PROCESS FOR IMPROVING ENANTIOMERIC PURITY OF ALDEHYDES

Abstract: This invention relates to a process for producing an optically active aldehyde (first aldehyde) containing a reduced amount of the corresponding enantiomeric aldehyde (second aldehyde) which process comprises: (1) providing an initial solution containing a non-eutectic mixture of the first aldehyde and the second aldehyde, which mixture has a composition in the compositional region where only the first aldehyde crystallizes when its solubility limit in the solution is exceeded, and (2) maintaining the solution at a temperature above the eutectic temperature of the mixture and under conditions such that the solubility limit of the first aldehyde is exceeded so as to form a crystalline first aldehyde containing relatively less of the second aldehyde than was present in the initial solution.

Description: PROCESS FOR IMPROVING ENANTIOMERIC PURITY OF ALDEHYDES Related Application This application is a continuation-in-part of U. S. Application Serial No. 08/265,207, filed June 24, 1994. " Brief Summary of the Invention Technical Field This invention relates to a process for improving the enantiometric purity of mixtures of optically active aldehyde isomers. Background of the Invention Asymmetric synthesis is of importance, for example, in the pharmaceutical industry, since frequently only one optically active isomer (enantiomer) is therapeutically active. An example of such a pharmaceutical product is the non-steroidal anti- inflammatory drug naproxen. The S enantiomer is a potent anti- arthritic agent while the R enantiomer is a Hver toxin. It is therefore oftentimes desirable to selectively produce one particular enantiomer over its mirror image. It is known that special precautions must be taken to ensure production of a desired enantiomer because of the tendency to produce optically inactive racemic mixtures, that is equal amounts of each mirror image enantiomer whose opposite optical activities cancel out each other. In order to obtain the desired enantiomer (or mirror image stereoisomer) from such a racemic mixture, the racemic mixture must be separated into its optically active components. This separation, known as optical resolution, may be carried out by actual physical sorting, direct crystallization of the racemic mixture, or other methods known in the art (see, for example, U.S. Patent 4,242,193). Such optical resolution procedures are often laborious and expensive as well as destructive to the desired enantiomer. Due to these difficulties, increased attention has been placed upon asymmetric synthesis in which one of the enantiomers is obtained in significantly greater amounts than the other enantiomer. Efficient asymmetric synthesis desirably affords the ability to control both regioselectivity (branched/normal isomer ratio in hydroformylation of terminal olefins) and stereoselectivity. Various asymmetric synthesis catalysts have been described in the art. For example, Wink, Donald J. et al., Inorg. Chem. 1990, 29, 5006-5008 discloses the synthesis of chelating bis(dioxaphospholane) ligands through chlorodioxaphospholane intermediates and the utility of bis(phosphite)rhodium cations in hydrogenation catalysis. A complex derived from dihydrobenzoin was tested as a precursor in the hydroformylation of olefins and gave a racemic mixture. Cationic rhodium complexes of bis(dioxaphospholane) ligands were tested in the hydrogenation of enamides and gave enantiomeric excesses on the order of 2-10%. Pottier, Y. et al., Journal of Organometallic Chemistry, 370, 1989, 333-342 describes the asymmetric hydroformylation of styrene using rhodium catalysts modified with aminophosphine- phosphinite ligands. Enantioselectivities greater than 30% ee are reportedly obtained. East Germany Patents Nos. 275,623 and 280,473 relate to chiral rhodium carbohydrate-phosphinite catalyst production. The catalysts are stated to be useful as stereospecific catalysts for carrying out carbon-carbon bond formation, hydroformylation, hydrosilylation, carbonylation and hydrogenation reactions to give optically active compounds. Stille et al., OrganometalHcs 1991, 10, 1183-1189 relates to the synthesis of three complexes of platinum Il-containing the chiral ligands: l-(tert-butoxycarbonyl)-(2S, 4S)-2-[(diphenyl- phosphino)methyl]-4-(dibenzophospholyl)pyrrolidine; l-(tert- butoxycarbonyl)-(2S,4S)-2-[(dibenzophos- pholyl)methyl]-4- (diphenylphosph_no)pyrrolidine; and l-(tert-butoxycarbonyl)-(2S,4S)- 4-(dibenzophospholyl)-2-[(dibenzophospholyl)methyl]pyrrohdine. Asymmetric hydroformylation of vinyl arenes (including methoxyvinylnaphthalene) was examined with use of platinum complexes of these three Hgands in the presence of stannous chloride as catalyst. Various branched normal ratios (0.5-3.2) and enantiomeric excess values (12-77%) were obtained. When the reactions were carried out in the presence of triethyl orthoformate to improve on the enantiomeric purity of the products, aU four catalysts gave virtually complete enantioselectivity (ee>96%) and similar branched normal ratios. A similar disclosure appears in published PCT patent appHcation WO 88/08835 PubHshed Patent Cooperation Treaty Patent AppHcation 93/03839 (Babin et al.) relates to asymmetric syntheses processes in which a prochiral or chiral compound is reacted in the presence of an optically active metal-Hgand complex catalyst to produce an optically active product. The processes of Babin et al. are distinctive in that they provide good yields of optically active products having high stereoselectivity, high regioselectivity, and good reaction rate without the need for optical resolution. The processes of Babin et al. stereoselectively produce a chiral center. An advantage of the processes of Babin et al. is that optically active products can be synthesized from optically inactive reactants. Another advantage of the processes of Babin et al. is that yield losses associated with the production of an undesired enantiomer can be substantially reduced. The asymmetric syntheses processes of Babin et al. are useful for the production of numerous optically active organic compounds, e.g., aldehydes, alcohols, ethers, esters, amines, amides, carboxylic acids and the like, which have a wide variety of appHcations. Despite the remarkable advance in the art represented by Babin et al, there remains further room for improvement with respect to the enantiomeric purity of the optically active aldehyde isomers produced by the Babin et al. processes. Enantiomeric purification of enantiomerically enriched compounds (e.g., by crystalHzation) is a well known process and has been observed for many compounds. However, the ability to purify a chiral product via crystalHzation varies widely from compound to compound and even closely related compounds may behave very differently. There appears to be no prior art relating to the enantiomeric purification of enantiomericaUy enriched aldehyde mixtures, particularly mixtures of R- and S-2-(6-methoxy-2- naphthyDpropionaldehyde, by crystaUization. The foUowing pubHcations are illustrative of prior art related to the crystalHzation of S-ibuprofen and S-naproxen acids, their sodium salts and 2-(6- methoxy-2-naphthyl)propionitrile from enantiomeric mixtures thereof. These references do not disclose crystalHzation of enantiomeric aldehyde mixtures. Manimaran, T.; Stahly, G.P. Tetrahedron: Asymmetry 1993, 4, 1949, Optical Purification of Profen Drugs," discloses the crystalHzation of the sodium salts of S-ibuprofen and S-naproxen. CrystalHzation of the sodium salts results in significant improvement in the enantiomeric purity of the product. The article includes phase diagrams for S-ibuprofen and S-naproxen acids and several salts of each. The article also describes some fundamental principles governing the enantiomeric purification of products via crystallization. Manimaran, T.; Stahly, G.P.; Herndon, C.R., Jr. U.S. Patent 5,248,813, 1993, "Enantiomeric Resolution," discloses the crystalHzation of various Ibuprofen salts as a means of improving enantiomeric purity. Pringle, P.; Murray, W.T.; Thompson, D.K.; Choudhury, A.A.; Patil, D.R. U.S. Patent 5,260,482, 1993, "Enantiomeric Resolution," discloses the use of hydrates of the sodium salt of ibuprofen in crystalHzation processes which result in enantiomeric purification of the product. Rajanbabu, T.V.; Casalnuovo, A.L. J. Am. Chem. Soc. 1992, 114, 6265, "Tailored Ligands for Asymmetric Catalysis: The Hydrocyanation of Vinylarenes," discloses the preparation and use of catalysts for the hydrocyanation of vinylarenes as a route for the preparation of S-ibuprofen and S-naproxen. The authors comment, although no experimental details are given, that enantiomericaUy enriched mixtures of 2-(6-methoxy-2-naphthyl)propionitrile may be purified by crystallization. The prior art relating to enantiomeric aldehyde mixtures does not disclose the use of crystalHzation to separate the enantiomers from each other. Thus, in the StiUe et al. article discussed above, there is no mention of crystalHzing aldehyde mixtures to improve their enantiomeric purity. Babin et al. discussed above discloses: "The desired opticaUy active products, e.g., aldehydes, may be recovered in any conventional manner. Suitable separation techniques include, for example, solvent extraction, crystalHzation, distiUation, vaporization, wiped film evaporation, falling film evaporation and the like. It may be desired to remove the optically active products from the reaction system as they are formed through the use of trapping agents as described in WO Patent 88/08835." Babin et al. does not disclose the use of crystaUization to separate enantiomeric aldehydes from each other. Disclosure of the Invention This invention provides a process for producing an optically active aldehyde (first aldehyde) containing a reduced amount of the corresponding enantiomeric aldehyde (second aldehyde) which process comprises: (1) providing an initial solution containing a non-eutectic mixture of the first aldehyde and the second aldehyde, which mixture has a composition in the compositional region where only the first aldehyde crystalHzes when its solubility limit in the solution is exceeded, and (2) maintaining the solution at a temperature above the eutectic temperature of the mixture and under conditions such that the solubility limit of the first aldehyde in the solution is exceeded so as to form a crystalline first aldehyde containing relatively less of the second aldehyde than was present in the initial solution. Brief Description of Drawings Fig. 1 is a flow diagram illustrating a membrane separation system that can be employed in the practice of this invention. Fig. 2 is a phase diagram iUustrating the phenomena involved in the practice of this invention when conglommerates are involved. Fig. 3 is a phase diagram iUustrating the phenomena involved in the practice of this invention when racemic compounds are involved. Fig. 4 shows a membrane and associated equipment useful in the practice of this invention. Fig. 5 shows a crystalHzer useful in the practice of this invention. Fig. 6 shows another crystalHzer useful in the practice of this invention. Fig. 7 is a melting point diagram for R- and S-2-(6- methoxy-2-naphthyl)propionaldehyde. Fig. 8 is a solubiH ty diagram for R- and S-2-(6-methoxy-2- naphthyDpropionaldehyde in acetone. Fig. 9 and Fig. 10 summarize distribution coefficients for R- and S-2-(6-methoxy-2-naphthyl)propionaldehyde in acetone. Fig. 11 is a flow diagram iUustrating a preferred crystalHzation scheme that can be employed in the practice of this invention. Detailed Description Forming Aldehyde Mixture This invention encompasses first providing a suitable enantiomeric aldehyde mixture. Such mixtures can be provided by such known processes as non-asymmetric processes (e.g., non- asymmetric hydroformylation, non-asymmetric olefin isomerization or non-asymmetric aldol condensation) foUowed by conventional resolution processes (e.g., chiral chromatography, kinetic resolution or other known resolution methods). However, the enantiomeric aldehyde mixtures are preferably provided by carrying out any known conventional non-asymmetric syntheses of aldehyde mixtures in an asymmetric fashion. In such preferred processes, the catalyst of a conventional non-asymmetric synthesis is replaced by an opticaUy active metal-Hgand complex catalyst and the process is conducted to produce a suitable optically active aldehyde mixture. Illustrative such asymmetric syntheses processes include, for example, asymmetric hydroformylation, asymmetric olefin isomerization and asymmetric aldol condensation. Preferably, the first step of the process of this invention comprises forming an enantiomeric aldehyde mixture by asymmetric hydroformylation. Such asymmetric hydroformylation processes involve the use of an opticaUy active metal-phosphorus Hgand complex catalyst and, optionaUy, free Hgand to produce optically active aldehydes by reacting a prochiral or chiral olefinic compound with carbon monoxide and hydrogen. The opticaUy active aldehydes produced in this preferred first step of the process of this invention are compounds obtained by the addition of a formyl group to an olefinically unsaturated carbon atom in the starting material with simultaneous saturation of the olefinic bond. The processing techniques of this preferred first step of the process of this invention may correspond to any of the known processing techniques heretofore employed in conventional asymmetric syntheses reactions, including asymmetric hydroformylation reactions. For instance, the asymmetric syntheses processes can be conducted in continuous, semi-continuous or batch fashion and can involve a liquid recycle operation if desired. This step of processes of this invention are preferably conducted in batch fashion. Likewise, the manner or order of addition of the reaction ingredients, catalyst and solvent are also not critical and may be accomplished in any conventional fashion. Alternatively, as the first step in the process of this invention, asymmetric olefin isomerization can be carried out in accordance with conventional procedures known in the art to produce the enantiomeric aldehyde mixtures used in this invention. For example, aUyHc alcohols can be isomerized under isomerization conditions in the presence of an opticaUy active metal-Hgand complex catalyst described herein to produce opticaUy active aldehydes. Also alternatively, as the first step in the process of this invention, asymmetric aldol condensation can be carried out in accordance with conventional procedures known in the art to produce the enantiomeric aldehyde mixtures used in this invention. For example, opticaUy active aldehydes can be prepared by reacting a prochiral aldehyde and a silyl enol ether under aldol condensation conditions in the presence of an opticaUy active metal-Hgand complex catalyst described herein. In general, the above-mentioned asymmetric synthesis processes are carried out in a Hquid reaction medium that contains a solvent for the optically active catalyst, preferably one in which the reaction ingredients including catalyst are substantially soluble. In addition, it may be desired that the asymmetric syntheses processes be effected in the presence of free Hgand as well as in the presence of the optically active complex catalyst. By "free Hgand" is meant Hgand that is not complexed with the metal atom in the opticaUy active complex catalyst. The prochiral and chiral starting materials useful in the processes for producing the enantiomeric aldehyde mixtures employed in the process of the present this invention are chosen depending on the particular asymmetric synthesis process that is used. Such starting materials are weU known in the art and can be used in conventional amounts in accordance with conventional methods. IUustrative starting material reactants include, for example, substituted and unsubstituted aldehydes (for aldol condensation processes), prochiral olefins (for hydroformylation processes) and ketones (for aldol condensation processes) and the like. IUustrative olefin starting material reactants useful in certain of the asymmetric synthesis processes useful in producing the enantiomeric aldehyde mixtures employed in this invention (e.g., asymmetric hydroformylation) include those which can be terminally or internally unsaturated and be of straight chain, branched-chain or cycHc structure. Such olefins can contain from 2 to 40 carbon atoms or greater and may contain one or more ethylenic unsaturated groups. Moreover, such olefins may contain groups or substituents which do not essentiaUy adversely interfere with the asymmetric syntheses process such as carbonyl, carbonyloxy, oxy, hydroxy, oxycarbonyl, halogen, alkoxy, aryl, haloalkyl, and the like. Illustrative olefinic unsaturated compounds include substituted and unsubstituted alpha olefins, internal olefins, alkyl alkenoates, alkenyl alkanoates, alkenyl alkyl ethers, alkenols and the like, e.g., 1- butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1- octadecene, 2-butene, isoamylene, 2-pentene, 2-hexene, 3-hexene, 2- heptene, cyclohexene, propylene dimers, propylene trimers, propylene tetramers, 2-ethylhexene, 3-phenyl-l-propene, 1,4- hexadiene, 1,7-octadiene, 3-cyclohexyl-l-butene, aUyl alcohol, hex-1- en-4-ol, oct-l-en-4-ol, vinyl acetate, aUyl acetate, 3-butenyl acetate, vinyl propionate, aUyl propionate, aUyl butyrate, methyl methacrylate, 3-butenyl acetate, vinyl ethyl ether, aUyl ethyl ether, n- propyl-7-octenoate, 3-butenenitrile, 5-hexenamide, styrene, norbornene, alpha-methylstyrene and the like. IUustrative preferred olefinic unsaturated compounds include, for example, p- isobutylstyrene, 2-vinyl-6-methoxy-2-naphthylene, 3-ethenylphenyl phenyl ketone, 4-ethenylphenyl-2-thienylketone, 4-ethenyl-2- fluorobiphenyl, 4-(l,3-dihydro-l-oxo-2H-isoindol-2-yl)styrene, 2- ethenyl-5-benzoylthiophene, 3-ethenylphenyl phenyl ether, propenylbenzene, isobutyl-4-propenylbenzene, phenyl vinyl ether, vinyl chloride and the like. Suitable olefinic unsaturated compounds useful in certain asymmetric syntheses processes of this invention include substituted aryl ethylenes described in U.S. Patent 4,329,507, the disclosure of which is incorporated herein by reference. Mixtures of different olefinic starting materials can be employed, if desired, in the asymmetric syntheses processes used as the first step in the process of this invention. More preferably, the first step involves hydroformylating alpha olefins containing from 4 to 40 carbon atoms or greater and internal olefins containing from 4 to 40 carbon atoms or greater or mixtures of such alpha olefins and internal olefins. IUustrative prochiral and chiral olefins useful in the processes that can be employed to produce the enantiomeric aldehyde mixtures that can be employed in this invention include those represented by the formula: wherein R.. , R 2 , RO and R 4 are the same or different (provided R-. is different from Ro or Rn is different from R.) and are selected from hydrogen; alkyl; substituted alkyl, said substitution being selected from dialkylamino such as benzylamino and dibenzylamino, alkoxy such as methoxy and ethoxy, acyloxy such as acetoxy, halo, nitro, nitrile, thio, carbonyl, carboxamide, carboxaldehyde, carboxyl, carboxyHc ester; aryl including phenyl; substituted aryl including phenyl, said substitution being selected from alkyl, amino including alkylamino and dialkylamino such as benzylamino and dibenzylamino, hydroxy, alkoxy such as methoxy and ethoxy, acyloxy such as acetoxy, halo, nitrile, nitro, carboxyl, carboxaldehyde, carboxyHc ester, carbonyl, and thio; acyloxy such as acetoxy; alkoxy such as methoxy and ethoxy; amino including alkylamino and dialkylamino such as benzylamino and dibenzylamino; acylamino and diacylamino such as acetylbenzylamino and diacetylamino; nitro; carbonyl; nitrile; carboxyl; carboxamide; carboxaldehyde; carboxylic ester; and alkylmercapto such as methylmercapto. It is understood that the prochiral and chiral olefins of this definition also include molecules of the above general formula where the R-groups are connected to form ring compounds, e.g., 3-methyl-l-cyclohexene, and the like. The opticaUy active catalyst useful in producing the aldehyde mixtures that are employed in this invention includes an opticaUy active metal-Hgand complex catalyst in which the Hgand is opticaUy active, preferably opticaUy pure. The permissible metals which make up the opticaUy active metal-Hgand complexes include Group VIII metals selected from rhodium (Rh), cobalt (Co), iridium (Ir), ruthenium (Ru), iron (Fe), nickel (Ni), paUadium (Pd), platinum (Pt), osmium (Os) and mixtures thereof, with the preferred metals being rhodium, cobalt, iridium and ruthenium, more preferably rhodium and ruthenium, especially rhodium. Other permissible metals include Group IB metals selected from copper (Cu), sUver (Ag), gold (Au) and mixtures thereof, and also Group VIB metals selected from chromium (Cr), molybdenum (Mo), tungsten (W) and mixtures thereof. Mixtures of metals from Group VIII, Group IB and Group VIB may be used in this invention. It is to be noted that the successful practice of this invention does not depend and is not predicated on the exact structure of the opticaUy active metal-Hgand complex species, which may be present in their mononuclear, dinuclear and or higher nuclearity forms, provided the Hgand is opticaUy active. Indeed, the exact opticaUy active structure is not known. Although it is not intended herein to be bound to any theory or mechanistic discourse, it appears that the opticaUy active catalytic species may in its simplest form consist essentiaUy of the metal in complex combination with the opticaUy active Hgand and, in hydroformylation, carbon monoxide, hydrogen and an olefin. The term "complex" as used herein and in the claims means a coordination compound formed by the union of one or more electronically rich molecules or atoms capable of independent existence with one or more electronically poor molecules or atoms, each of which is also capable of independent existence. For example, the preferred optically active Hgands employable herein, i.e., phosphorus Hgands, may possess one or more phosphorus donor atoms, each having one avaUable or unshared pair of electrons which are each capable of orming a coordinate covalent bond independently or possibly in concert (e.g., via chelation) with the metal. As can be surmised from the above discussions, carbon monoxide (which is also properly classified as Hgand) can also be present and complexed with the metal. The ultimate composition of the optically active complex catalyst may also contain an additional Hgand, e.g., hydrogen or an anion satisfying the coordination sites or nuclear charge of the metal. IUustrative additional Hgands include, e.g., halogen (Cl, Br, I), alkyl, aryl, substituted aryl, acyl, CF3, C2F5, CN, R 2 PO and RP(0)(OH)0 (wherein each R is alkyl or aryl), acetate, acetylacetonate, S0 4 , PF 4 , PF g , N0 2 , NOg, CHgO, CH 2 =CHCH 2 , CgHgCN, CH 3 CN, NO, NHg, pyridine, (C 2 Hg)gN, mono-olefins, diolefins and triolefins, tetrahydrofuran, and the like. It is of course to be understood that the opticaUy active complex spedes is preferably free of any additional organic Hgand or anion that might poison the catalyst and have an undue adverse effect on catalyst performance. It is preferred in the rhodium-catalyzed asymmetric hydroformylation reactions of this invention that the active catalysts be free of halogen and sulfur directly bonded to the rhodium, although such may not be absolutely necessary. The number of available coordination sites on such metals is weU known in the art. Thus the opticaUy active spedes may comprise a complex catalyst mixture, in their monomeric, dimeric or higher nudearity forms, which are preferably characterized by at least one phosphorus-containing molecule complexed per one molecule of rhodium. As noted above, it is considered that the optically active spedes of the preferred rhodium catalyst employed in this invention during asymmetric hydroformylation may be complexed with carbon monoxide and hydrogen in addition to the opticaUy active phosphorus Hgands in view of the carbon monoxide and hydrogen gas employed by the asymmetric hydroformylation process. Moreover, regardless of whether the opticaUy active complex catalyst is formed prior to introduction into the reaction zone or whether the active catalyst is prepared in situ during the reaction, the asymmetric synthesis processes (and espedally the asymmetric hydroformylation processes) may, if desired, be effected in the presence of free Hgand. The Hgands employable in producing the enantiomeric aldehyde mixtures useful in this invention include those opticaUy active ligands having the general formula: wherein each W is the same or different and is phosphorus, arsenic or antimony, each X is the same or different and is oxygen, nitrogen or a covalent bond l- aking W and Y, Y is an m-valent substituted or unsubstituted hydrocarbon residue, each Z is the same or different and is a substituted or unsubstituted hydrocarbon residue, preferably a hydrocarbon residue containing at least one heteroatom which is bonded to W, or the Z substituents bonded to W may be bridged together to form a substituted or unsubstituted cyclic hydrocarbon residue, preferably a cydic hydrocarbon residue containing at least 2 heteroatoms which are each bonded to W, and m is a value equal to the free valence of Y, preferably a value of from 1 to 6, provided at least one of Y and Z is opticaUy active. Referring to the above general formula, it is appredated that when m is a value of 2 or greater, the Hgand may include any combination of permissible cycHc hydrocarbon residues and/or acycHc hydrocarbon residues which satisfy the valence of Y. It is also appredated that the hydrocarbon residues represented by Z may include one or more heteroatoms and such heteroatom may be directly bonded to W. The optically active Hgands included in the above general structure should be easUy ascertainable by one skilled in the art. IUustrative opticaUy active ligands employable in the first step of the processes this invention include those of the formulae: wherein W, Y, Z and m are as defined hereinabove and Y" is the same or different and is hydrogen or a substituted or unsubstituted hydrocarbon residue. IUustrative preferred optically active Hgands encompassed by the above formulae include, for example, (poly)phosphites, (poly)phosphinites, (poly)phosphonites and the Hke. Illustrative preferred opticaUy active Hgands employable in this invention include the following: (i) optically active polyphosphites having the formula: wherein each Ar group is the same or different and is a substituted or unsubstituted aryl radical; Y is an m-valent substituted or unsubstituted hydrocarbon radical selected from alkylene, alkylene- oxy- alkylene, arylene and aιylene-(CH 2 ) -(Q) n -(CH 2 - arylene; each y is the same or different and is a value of 0 or 1; each n is the same or different and is a value of 0 or 1; each Q is the same or different and is a substituted or unsubstituted divalent bridging group selected from -CR 1 R 2 -, -0-, -S-, -NR 3 -, -SiR^ 5 - and -CO-, wherein R 1 and R 2 are the same or different and are hydrogen or a substituted or unsubstituted radical selected from alkyl of 1 to 12 carbon atoms, phenyl, tolyl and anisyl, and R , R and R are the same or different and are a radical selected from hydrogen or methyl; and m' is a value of from 2 to 6; (ii) opticaUy active diorganophosphites having the formula: wherein Y' is a substituted or unsubstituted monovalent hydrocarbon radical, and Ar, Q, n and y are as defined above; and (iii) opticaUy active open-ended bisphosphites having the formula: wherein Ar, Q, n, y, Y and Y are as defined above and Y can be the same or different. IUustrative aryl radicals of the Ar and Y groups of the above formulae include aryl moieties which may contain from 6 to 18 carbon atoms such as phenylene, naphthylene, anthracylene and the like. In the above formulae, preferably m is fro 2 to 4 and each y and each n has a value of 0. However, when n is 1, Q preferably is a 1 2 -CR R - bridging group as defined above and more preferably methylene (-CHo-) or alkyHdene (-CHR 2 -), wherein R 2 is an alkyl radical of 1 to 12 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, dodecyl, etc.), especially methyl. The m-valent hydrocarbon radicals represented by Y in the polyphosphite Hgand formula above are hydrocarbons containing from 2 to 30 carbon atoms selected from alkylene, alkylene-oxy- alkylene, arylene, and arylene-(-CH 2 -) -(Q) -(-CHg-) v - arylene radicals, wherein Q, n and y are the same as defined above. Preferably the alkylene moieties of said radicals contain from 2 to 18 carbon atoms and more preferably from 2 to 12 carbon atoms, whUe the arylene moieties of said radicals preferably contain from 6 to 18 carbon atoms. The divalent bridging group represented by Y in the open-ended bisphosphite Hgand formula above are divalent hydrocarbons containing from 2 to 30 carbon atoms selected from alkylene, alkylene-oxy-alkylene, arylene and arylene-(-CH2-)y-(Q) n- (-CH2-) y-arylene radicals, wherein Q, n and y are the same as defined above. Preferably the alkylene moieties of said radicals contain from 2 to 18 carbon atoms and more preferably from 2 to 12 carbon atoms, while the arylene moieties of said radicals preferably contain from 6 to 18 carbon atoms. Hydrocarbon radicals represented by Y in the above phosphite Hgand formulae include monovalent hydrocarbon radicals containing from 1 to 30 carbon atoms selected from alkyl radicals including linear or branched primary, secondary or tertiary alkyl radicals, such as methyl, ethyl, n-propyl, isopropyl, amyl, sec-amyl, t-amyl, 2-ethylhexyl and the like; aryl radicals such as phenyl, naphthyl and the like; aralkyl radicals such as benzyl, phenylethyl, tri-phenylmethylethane and the like; alkaryl radicals such as tolyl, xylyl and the Hke; and cycloalkyl radicals such as cyclopentyl, cyclohexyl, cyclohexylethyl and the like. Preferably, Y is selected from alkyl and aryl radicals which contain from about 1 and 30 carbon atoms. Preferably, the alkyl radicals contain from 1 to 18 carbon atoms, most preferably from 1 to 10 carbon atoms, whUe the aryl, aralkyl, alkaryl and cycloalkyl radicals preferably contain from 6 to 18 carbon atoms. Further, although each Y' group in the open- ended bisphosphite Hgand formula above may differ from the other, preferably they are identical. The aryl radicals in the above formulae may also be substituted with any substituent radical that does not unduly adversely affect the processes of this invention. Illustrative substituents include radicals αmteining from 1 to 18 carbon atoms such as alkyl, aryl, aralkyl, alkaryl and cycloalkyl radicals; alkoxy radicals; sUyl radicals such as -Si(R 9 )g and -Si(OR 9 )g * , amino radicals such as -N(R 9 )«; acyl radicals such as -C(0)R 9 ; acyloxy radicals such as -OC(0)R 9 ; carbonyloxy radicals such as -COOR 9 ; amido radicals such as -C(0)N(R 9 ) 2 and -N(R 9 )COR 9 ; sulfonyl radicals such as -SOoR 9 , sulfinyl radicals such as -SO (R 9 ) 2 ; thionyl radicals such as -SR 9 ; phosphonyl radicals such as -P(0)(R 9 ) 2 ; as well as halogen, nitro, cyano, trifluoromethyl and hydroxy radicals Q and the like, wherein each R can be a monovalent hydrocarbon radical such as alkyl, aryl, alkaryl, aralkyl and cycloalkyl radicals, with the provisos that in amino substitutents such as -N(R )„, each Q R taken together can also comprise a divalent bridging group that forms a heterocycHc radical with the nitrogen atom, in amido substituents such as -C(0)N(R 9 ) 2 and -N(R 9 )COR 9 , each R 9 bonded to N can also be hydrogen, and in phosphonyl substituents such as -P(0)(R 9 ) 2 , one R 9 can be hydrogen. It is to be understood that each R9 group in a particular substituent may be the same of different. Such hydrocarbon substituent radicals could possibly in turn be substituted with a substituent such as already herein outlined above provided that any such occurrence would not unduly adversely effect the processes of this invention. At least one ionic moiety selected from salts of carboxyHc add and of sulfonic add may be substituted on an aryl moiety in the above formulae. Among the more preferred phosphite ligands useful in the first step in the process of this invention are those Hgands wherein the two Ar groups linked by the bridging group represented by -(CH2)y-(Q) n-(CH2)y- in the above formulae are bonded through their ortho positions in relation to the oxygen atoms that connect the Ar groups to the phosphorus atom. It is also preferred that any substituent radical, when present on such Ar groups, be bonded in the para and or ortho position on the aryl in relation to the oxygen atom that bonds the substituted Ar group to its phosphorus atom. IUustrative monovalent hydrocarbon residues represented by the Z, Y, Y' and Y" groups in the above formulae include substituted or unsubstituted monovalent hydrocarbon radicals containing from 1 to 30 carbon atoms selected from substituted or unsubstituted alkyl, aryl, alkaryl, aralkyl and aHcycHc radicals. While each Z and Y" group in a given formula may be individually the same or different, preferably they are both the same. More spedfic iUustrative monovalent hydrocarbon residues represented by Z, Y, Y 1 and Y" include primary, secondary and tertiary chain alkyl radicals such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, t-butyl, neo-pentyl, sec-amyl, t-amyl, iso-octyl, 2- ethyUiexyl, iso-nonyl, iso-decyl, octadecyl and the like; aryl radicals such as phenyl, naphthyl, anthracyl and the like; aralkyl radicals such as benzyl, phenylethyl and the like; alkaryl radicals such as tolyl, xylyl, p-alkylphenyls and the like; and alicycHc radicals such as cyclopentyl, cyclohexyl, cyclooctyl, cyclohexylethyl, 1- methylcyclohexyl and the like. Preferably the unsubstituted alkyl radicals may contain from 1 to 18 carbon atoms, more preferably from 1 to 10 carbon atoms, while the unsubstituted aryl, aralkyl, alkaryl and alicycHc radicals preferably contain from 6 to 18 carbon atoms. Among the more preferred Z, Y, Y" and Y" residues are phenyl and substituted phenyl radicals. IUustrative divalent hydrocarbon residues represented by Z, Y and Y in the above formulae include substituted and unsubstituted radicals selected from alkylene, -alkylene-oxy- alkylene, arylene, -arylene-oxy-arylene-, aHcycHc radicals, phenylene, naphthylene, -arylene-(CH2)y(Q)n(CH2)y-arylene- such as -phenylene-(CH2)y(Q)n(CH2)y-phenylene- and -naphthylene- (CH2)y(Q)n(CH2)y-naphthylene-radicals, wherein Q, y and n are as defined hereinabove. More specific iUustrative divalent radicals represented by Z, Y and Y indude, e.g., 1,2-ethylene, 1,3-propylene, 1,6-hexylene, 1,8-octylene, 1,12-dodecylene, 1,4-phenylene, 1,8- naphthylene, l,l'-biphenyl-2,2'-diyl, l,l , -binaphthyl-2,2 , -diyl, 2,2 * - binaphthyl-ljl'-diyl and the like. The alkylene radicals may contain from 2 to 12 carbon atoms, whUe the arylene radicals may contain from 6 to 18 carbon atoms. Preferably Z is an arylene radical, Y is an alkylene radical and Y is an alkylene radical. Moreover, the above-described radicals represented by Z, Y, Ar, Y and Y' of the above formulae, may be further substituted with any substituent that does not unduly adversely effect the desired results of this invention. IUustrative substituents are, for example, monovalent hydrocarbon radicals having between one and about 18 carbon atoms, such as alkyl, aryl, alkaryl, aralkyl, cycloalkyl and other radicals as defined above. In addition, various other substituents that may be present include, e.g., halogen, preferably chlorine or fluorine, -N0 2 , -CN, -CFg, -OH, -Si(CHg)g, -Si(OCHg)g, -Si(C 3 H 7 )g, -C(0)CHg, -C(0)C 2 H 5 , -OC(0)CgH 5 , -C(0)OCHg, -N(CH 3 ) 2 , -NH 2 , -NHCHg, -NH(C 2 H 5 ), -CONH 2 , -CON(CHg) 2 , -S(0) 2 C 2 H 5 , -OCHg, -OC 2 H 5 , -OC 6 H 5 , -C(0)C 6 H 5 , -0(t-C 4 H 9 ), -SC 2 H 5 , -OCH 2 CH 2 OCH 3 , -(OCH 2 CH 2 ) 2 OCHg, -(OCH 2 CH 2 )gOCHg, -SCHg, -S(0)CH 3 , -SC 6 H 5 , -P(0)(C 6 H 5 ) 2 , -P(OXCHg) 2 , -P(0)(C 2 H 5)2 , -P(0)(C 3 H 7 ) 2 , -P(0)(C 4 H 9 ) 2 , -P(0)(C 6 H 13 ) 2 , -P(0)CHg(C 6 H 5 ), -P(0)(H)(C 6 H 5 ), -NHC(0)CHg and the like. Moreover, each Z, Y, Ar, Y and Y' group may contain one or more such substituent groups which may also be the same or different in any given Hgand molecule. Preferred substituent radicals include alkyl and alkoxy radicals containing from 1 to 18 carbon atoms and more preferably from 1 to 10 carbon atoms, espedaUy t-butyl and methoxy. As used herein, the term "substituted" is contemplated to include all permissible substituents of organic compounds. In a broad aspect, the permissible substituents include acycHc and cycHc, branched and unbranched, carbocycHc and heterocyclic, aromatic and nonaromatic substituents of organic compounds. IUustrative substituents include, for example, those described hereinabove. The permissible substituents can be one or more and the same or different for appropriate organic compounds. For purposes of this invention, the heteroatoms such as nitrogen may have hydrogen substituents and/or any permissible substituents of organic compounds described herein which satisfy the valendes of the heteroatoms. This invention is not intended to be Hmited in any manner by the permissible substituents of organic compounds. The optically active Hgands employed in the complex catalysts useful in the first step of the process of this invention are uniquely adaptable and suitable for asymmetric syntheses processes, espedaUy rhodium-catalyzed asymmetric hydroformylation. For instance, the opticaUy active phosphorus Hgands may provide very good rhodium complex stabiHty in addition to providing good catalytic activity for the asymmetric hydroformylation of aU types of permissible olefins. Further, their unique chemical structure should provide the Hgand with very good stabiHty against side reactions such as being hydrolyzed during asymmetric hydroformylation, as weU as upon storage. The types of novel optically active Hgands of the generic class employable in the first step of the process of this invention can be prepared by methods known in the art. For instance, the optically active phosphorus ligands employable in this invention can be prepared via a series of conventional phosphorus haHde-alcohol or amine condensation reactions in which at least one of the alcohol or amine ingredients is optically active or opticaUy pure. Such types of condensation reactions and the manner in which they may be conducted are weU known in the art. Moreover, the phosphorus Hgands employable herein can be readUy identified and characterized by conventional analytical techniques, such as Phosphorus-31 nuclear magnetic resonance spectroscopy and Fast Atom Bombardment Mass Spectroscopy if desired. As noted above, the opticaUy active Hgands can be employed as both the Hgand of the above-described opticaUy active metal-Hgand complex catalyst as weU as the free Hgand that can be present in the reaction medium of the processes of this invention. In addition, while the opticaUy active Hgand of the metal-Hgand complex "catalyst and any excess free Hgand preferably present in a given process of this invention are normaUy the same Hgand, different opticaUy active Hgands, as well as mixtures of two or more different opticaUy active Hgands, may be employed for each purpose in any given process. The opticaUy active metal-Hgand complex catalysts of this invention may be formed by methods known in the art. See, for example, U.S. Patent Nos. 4,769,498, 4,717,775, 4,774,361, 4,737,588, 4,885,401, 4,748,261, 4,599,206, 4,668,651, 5,059,710 and 5,113,022, aU of which are incorporated herein by reference. For instance, preformed metal hydrido-carbonyl catalysts may possibly be prepared and introduced into the reaction medium of an asymmetric syntheses process. More preferably, the metal-Hgand complex catalysts of this invention can be derived from a metal catalyst precursor which may be introduced into the reaction medium for in situ formation of the active catalyst. For example, rhodium catalyst precursors such as rhodium dicarbonyl acetylacetonate, Rh 2 Og, Rh 4 (CO)-, 2 , Rhg(CO)., g, Rh(NOo) o and the like may be introduced into the reaction medium along with the Hgand for the in situ formation of the active catalyst. In a preferred embodiment, rhodium dicarbonyl acetylacetonate is employed as a rhodium precursor and reacted in the presence of a solvent with a phosphorus Hgand compound to form a catalytic rhodium-phosphorus complex precursor which is introduced into the reactor, optionaUy along with excess free phosphorus Hgand, for the in situ formation of the active catalyst. In any event, it is sufϊϊdent for the purpose of this invention to understand that an opticaUy active metal-Hgand complex catalyst is present in the reaction medium under the conditions of the asymmetric syntheses and more preferably asymmetric hydroformylation process. Moreover, the amount of opticaUy active complex catalyst present in the reaction medium need only be that minimum amount necessary to provide the given metal concentration desired to be employed and which wiU furnish the basis for at least that catalytic amount of metal necessary to catalyze the particular asymmetric syntheses process desired. In general, metal concentrations in the range of from about 1 ppm to about 10,000 ppm, calculated as free metal, and Hgand to metal mole ratios in the catalyst ranging from about 0.5:1 to about 200:1, should be suffident for most asymmetric syntheses processes. Moreover, in the rhodium catalyzed asymmetric hydroformylation processes of this invention, it is generaUy preferred to employ from about 10 to 1000 ppm of rhodium and more preferably from 25 to 750 ppm of rhodium, calculated as free metal. A further aspect of the first step of the process of this invention involves the use of a catalyst precursor composition consisting essentially of a solubiHzed metal-Hgand complex precursor catalyst, an organic solvent and free Hgand. Such precursor compositions may be prepared by forming a solution of a metal starting material, such as a metal oxide, hydride, carbonyl or salt e.g., a nitrate, which may or may not be in complex combination with an optically active Hgand, an organic solvent and a free Hgand as defined herein. Any suitable metal starting material may be employed, e.g., rhodium dicarbonyl acetylacetonate, Rh 2 Og, Rh 4 (CO) 12 , Rhg(CO)- j 6 , Rh(NOg)g, poly-phosphite rhodium carbonyl hydrides, iridium carbonyl, poly-phosphite iridium carbonyl hydrides, osmium halide, chlorosmic add, osmium carbonyls, palladium hydride, palladous haHdes, platinic add, platinous halides, ruthenium carbonyls, as weU as other salts of other metals and carboxylates of adds such as cobalt chloride, cobalt nitrate, cobalt acetate, cobalt octoate, ferric acetate, ferric nitrate, nickel fluoride, nickel sulfate, paUadium acetate, osmium octoate, iridium sulfate, ruthenium nitrate, and the like. Of course, any suitable solvent may be employed such as those employable in the asymmetric syntheses process desired to be carried out. The desired asymmetric syntheses process may of course also dictate the various amounts of metal, solvent and optically active Hgand present in the precursor solution. Optically active ligands if not already complexed with the initial metal may be complexed to the metal either prior to or in situ during the asymmetric syntheses process. The opticaUy active catalyst used in the first step of the process of this invention may optionaUy be supported. Advantages of a supported catalyst may indude ease of catalyst separation and Hgand recovery. IUustrative examples of supports include alumina, silica gel, ion-exchange resins, polymeric supports and the like. The process conditions employable in the asymmetric processes that can be employed in the first step of the process of this invention are chosen depending on the particular asymmetric synthesis process. Such process conditions are well known in the art. AU of the asymmetric syntheses processes useful in this invention can be carried out in accordance with conventional procedures known in the art. IUustrative reaction conditions for conducting the asymmetric syntheses processes of this invention are described, for example, in Bosnich, B., Asymmetric Catalysis, Martinus Nijhoff PubHshers, 1986 and Morrison, J ames D., Asymmetric Synthesis, Vol. 5, Chiral Catalysis, Academic Press, Inc., 1985, both of which are incorporated herein by reference. Depending on the particular process, operating temperatures can range from about -80°C or less to about 500°C or greater and operating pressures can range from about 1 psig or less to about 10,000 psig or greater. The reaction conditions for effecting the preferred asymmetric hydroformylation process that can be employed in the first step of the process of this invention may be those heretofore conventionally used and may comprise a reaction temperature of from about -25°C or lower to about 200°C and pressures ranging from about 1 to 10,000 psia. While the preferred asymmetric syntheses process is the hydroformylation of olefinicaUy unsaturated compounds carbon monoxide and hydrogen to produce opticaUy active aldehydes, it is to be understood that the opticaUy active metal- Hgand complexes may be employed as catalysts in other types of asymmetric syntheses processes to obtain good results. As noted, the first step of the preferred process of this invention involves the production of opticaUy active aldehydes via asymmetric hydroformylation of a prochiral or chiral olefinic unsaturated compound with carbon monoxide and hydrogen in the presence of an opticaUy active metal-phosphorus Hgand complex catalyst and, optionaUy, free phosphorus Hgand, espedally an optically active rhodium-phosphorus Hgand complex catalyst. While the optimization of the reaction conditions necessary to achieve the best results and efifidency desired are dependent upon experience in the utiHzation of this invention, only a certain measure of experimentation should be necessary to ascertain those conditions which are optimum for a given situation and such should be well within the knowledge of one skilled in the art and easUy obtainable by foUowing the more preferred aspects of this invention as explained herein and/or be simple routine experimentation. For instance, the total gas pressure of hydrogen, carbon monoxide and olefinic unsaturated starting compound of the preferred asymmetric hydroformylation process of this invention may range from about 1 to about 10,000 psia. More preferably, however, in the asymmetric hydroformylation of prochiral olefins to produce opticaUy active aldehydes, it is preferred that the process be operated at a total gas pressure of hydrogen, carbon monoxide and olefinic unsaturated starting compound of less than about 1500 psia, and more preferably less than about 1000 psia. The minimum total pressure of the reactants is not particularly critical and is limited predominately only by the amount of reactants necessary to obtain a desired rate of reaction. More specificaUy, the carbon monoxide partial pressure of the asymmetric hydroformylation process of this invention is preferably from about 1 to about 360 psia, and more preferably from about 3 to about 270 psia, while the hydrogen partial pressure is preferably about 15 to about 480 psia and more preferably from about 30 to about 300 psia. In general, the molar ratio of gaseous hydrogen to carbon monoxide may range from about 1:10 to 100:1 or higher, the more preferred hydrogen to carbon monoxide molar ratio being from about 1:1 to about 1:10. Higher molar ratios of carbon monoxide to gaseous hydrogen may generaUy tend to favor higher branched/normal isomer ratios. Further as rioted above, the preferred asymmetric hydroformylation process useful in the first step of the process of this invention may be conducted at a reaction temperature from about -25°C or lower to about 200°C. The preferred reaction temperature employed in a given process wiU of course be dependent upon the particular olefinic starting material and opticaUy active metal-Hgand complex catalyst employed as weU as the effidency desired. Lower reaction temperatures may generaUy tend to favor higher enantiomeric excesses (ee) and branched/normal ratios. In general, asymmetric hydroformylations at reaction temperatures of about 0°C to about 120 °C are preferred for aU types of olefinic starting materials. More preferably, alpha-olefins can be effectively hydroformylated at a temperature of from about 0°C to about 90°C wbile even less reactive olefins than conventional linear alpha- olefins and internal olefins as weU as mixtures of alpha-olefins and internal olefins are effectively and preferably hydroformylated at a temperature of from about 25°C to about 120°C. Indeed, in the rhodium-catalyzed asymmetric hydroformylation process of this invention, no substantial benefit is seen in operating at reaction temperatures much above 120°C and such is considered to be less desirable. The processes employed in the first step of the process of this invention are conducted for a period of time suffident to produce an enantiomeric aldehyde mixture. The exact reaction time employed is dependent, in part, upon factors such as temperature, nature and proportion of starting materials, and the like. The reaction time wiU normally be within the range of from about one- half to about 200 hours or more, and preferably from less than about one to about 10 hours. The asymmetric synthesis processes, preferably asymmetric hydroformylation processes, useful as the first step in the process of this invention can be carried out in either the Hquid or gaseous state and involve a batch, continuous Hquid or gas recycle system or combination of such systems. A batch system is preferred for conducting such processes. Preferably, such asymmetric hydroformylation involves a batch homogeneous catalysis process wherein the hydroformylation is carried out in the presence of both free phosphorus Hgand and any suitable conventional solvent as further described herein. The asymmetric synthesis processes, and preferably asymmetric hydroformylation process, useful as the first step in the process of this invention may be conducted in the presence of an organic solvent for the opticaUy active metal-Hgand complex catalyst. Depending on the particular catalyst and reactants employed, suitable organic solvents include, for example, alcohols, alkanes, alkenes, alkynes, ethers, aldehydes, ketones, esters, adds, amides, amines, aromatics and the like. Any suitable solvent which does not unduly adversely interfere with the intended asymmetric synthesis process can be employed and such solvents may include those heretofore commonly employed in known metal catalyzed processes. Increasing the dielectric constant or polarity of a solvent may generaUy tend to favor increased reaction rates and selectivity. Mixtures of one or more different solvents may be employed if desired. The amount of solvent employed is not critical to this invention and need only be that amount suffident to provide the reaction medi urn with the particular metal, substrate and product concentration desired for a given process. In general, the amount of solvent when employed may range from about 5 percent by weight up to about 95 percent by weight or more based on the total weight of the reaction medium. As noted above, the metal-Hgand-catalyzed asymmetric synthesis processes (and espedally the asymmetric hydroformylation process) useful as the first step in the process of this invention can be carried out in the presence of free Hgand, i.e., Hgand that is not complexed with the metal of the opticaUy active metal-Hgand complex catalyst employed. While it is preferred to employ a free Hgand that is the same as the Hgand of the metal-Hgand complex catalyst such ligands need not be the same in a given process, but can be different if desired. While the asymmetric syntheses and preferably asymmetric hydroformylation process may be carried out in any excess amount of free Hgand desired, the employment of free Hgand may not be absolutely necessary. Accordingly, in general, amounts of Hgand of from about 2 to about 100, or higher if desired, moles per mole of metal (e.g., rhodium) present in the reaction medium should be suitable for most purposes, particularly with regard to rhodium catalyzed hydroformylation; said amounts of Hgand employed being the sum of both the amount of Hgand that is bound (complexed) to the metal present and the amount of free (non-complexed) Hgand present. Of course, if desired, make-up Hgand can be suppHed to the reaction medium of the asymmetric hydroformylation process, at any time and in any suitable manner, to maintain a predetermined level of free Hgand in the reaction medium. The abiHty to carry out the processes useful as the first step of the process of this invention in the presence of free Hgand can be a benefidal aspect of this invention in that it removes the criticaHty of employing very low predse concentrations of Hgand that may be required of certain complex catalysts whose activity may be retarded when even any amount of free Hgand is also present during the process, particularly when large scale commerdal operations are involved, thus helping to provide the operator with greater processing latitude. As indicated above, the aldehyde-forming processes useful in this invention can be conducted in a batch or continuous fashion, with recycle of unconsumed st-arting materials if required. The reaction can be conducted in a single reaction zone or in a pluraHty of reaction zones, in series or in paraUel or it may be conducted batchwise or continuously in an elongated tubular zone or series of such zones. The materials of construction employed should be inert to the starting materials during the reaction and the fabrication of the equipment should be able to withstand the reaction temperatures and pressures. Means to introduce and/or adjust the quantity of starting materials or ingredients introduced batchwise or continuously into the reaction zone during the course of the reaction can be conveniently utiHzed in the processes espedaUy to maintain the desired molar ratio of the starting materials. The reaction steps may be effected by the incremental addition of one of the starting materials to the other. Also, the reaction steps can be combined by the joint addition of the starting materials to the opticaUy active metal-Hgand complex catalyst. When complete conversion is not desired or not obtainable, the starting materials can be separated from the product and then recycled back into the reaction zone. The processes may be conducted in either glass lined, stainless steel or similar type reaction equipment. The reaction zone may be fitted with one or more internal and/or external heat exchangers) in order to control undue temperature fluctuations, or to prevent any possible "runaway" reaction temperatures. The aldehyde-forming processes useful as the first step in the process of this invention are useful for preparing mixtures of substituted opticaUy active aldehydes. The aldehyde-forming processes useful in this invention stereoselectively produce a chiral center. IUustrative opticaUy aldehydes prepared by the processes of this invention include, for example, substituted aldehydes. IUustrative preferred opticaUy active aldehyde compounds prepared by the asymmetric hydroformylation process of this invention include, for example, S-2-(p-isobutylphenyl)-propionaldehyde, S-2-(6- methoxy-2-naphthyl)propionaldehyde, S-2-(3-benzoylphenyl)- propionaldehyde, S-2-(p-thienoylphenyl)propionaldehyde, S-2-(3- fluoro-4-phenyl)phenylpropionaldehyde, S-2-[4-(l,3-dihydro-l-oxo-2H- isoindol-2-yl)phenyl]propionaldehyde, S-2-(2-methylacetaldehyde)-5- benzoylthiophene and the like, πiustrative of suitable optically active compounds which can be prepared by the processes of this invention (including derivatives of the optically active compounds as described hereinbelow and also prochiral and chiral starting material compounds as described hereinabove) include those permissible compounds which are described in K k-Othmer, Encyclopedia of Chemical Technology, Third Edition, 1984, the pertinent portions of which are incorporated herein by reference, and The Merck Index, An Encyclopedia of Chemicals, Drugs and Biologicals, Eleventh Edition, 1989, the pertinent portions of which are incorporated herein by reference. The aldehyde-foπmng processes useful as the first step in the process of this invention can provide opticaUy active aldehydes having very high enantioselectivity and regioselectivity. Enantiomeric excesses of preferably greater than 50%, more preferably greater than 75% and most preferably greater than 90% can be obtained by such processes. Branched/normal molar ratios of preferably greater than 5:1, more preferably greater than 10:1 and most preferably greater than 25:1 can be obtained by such processes. In the process of this invention, the aldehyde mixtures may be separated from the other components of the crude reaction mixtures in which the aldehyde mixtures are produced by any suitable method. Suitable separation methods include, for example, solvent extraction, crystalHzation, distillation, vaporization, wiped film evaporation, falling film evaporation and the like. It may be desired to remove the optically active products from the crude reaction mixture as they are formed through the use of trapping agents as described in published Patent Cooperation Treaty Patent AppHcationWO 88/08835. A preferred method for separating the enantiomeric aldehyde mixtures from the other components of the crude reaction mixtures is by membrane separation. Such membrane separation can be achieved as set out below which for purposes of illustration, relates to the separation of a crude asymmetric hydroformylation reaction mixture. In membrane separation of a crude hydroformylation reaction product, a hydrophobic solvent-resistant membrane is used which allows the aldehyde mixture, any unreacted olefin and any solvent to pass through whUe retaining a substantial portion of the opticaUy active metal-phosphorus Hgand complex catalyst and any free Hgand. A flow diagram of a suitable membrane separation system is shown in Fig. 1. The membrane separation is a pressure- driven process and, typically, the pressure of the feed stream (i.e., the crude reaction product that is being separated) is about 400 to 500 pounds per square inch, although pressures as low as 50 pounds per square inch and as high as 1000 pounds per square inch can be used. The feed stream to the membrane is the crude reaction product comprising an opticaUy active, metal-phosphorus Hgand complex catalyst and any free Hgand dissolved in the aldehyde mixture, the unreacted olefin and any solvent used in the asymmetric hydroformylation. The "permeate" is the stream which has passed through the membrane, as compared to the feed stream, the permeate is at a greatly reduced pressure. TypicaUy, the permeate is near atmospheric pressure. The permeate contains a greatly reduced amount of optically active metal-phosphorus Hgand complex catalyst and any free Hgand dissolved in the bulk of the aldehyde, the unreacted olefin and any solvent. The "raffinate" stream (also caUed the "concentrate" or "non-permeate" stream) is the stream that does not pass through the membrane. The raffinate contains the bulk of the opticaUy active metal-phosphorus Hgand complex catalyst and any free Hgand dissolved in some aldehyde, unreacted olefin and any solvent. The raffinate stream is typicaUy only sHghtly lower in pressure than the feed stream. The raffinate stream can be recycled back to the hydroformylation reactor for reuse. The permeate stream can be repressurized if it is desired to remove more of the opticaUy active metal-phosphorus Hgand complex catalyst and any free Hgand catalyst and sent to another membrane to undergo separation again. Alternatively, the permeate stream can be sent to the next step of the process of this invention (crystalHzation) if the levels of catalyst and Hgand are acceptably low. Suitable membranes for the above separations are disclosed in pubHshed European Patent AppHcation 0 532,199 Al. Such membranes are a composite membranes which are substantiaUy insoluble in acetonitrile, ethanol, hexane, toluene, N- methylpyrroHdone, dimethylsulfόxide, dimethylformamide, dimethylacetamide, mixtures thereof with each other, and mixtures of any of the foregoing with water. The membranes comprise a substrate layer made from a polymer selected from copolymers and homopolymers of ethylenicaUy unsaturated nitriles, which substrate layer has been subjected to a stepwise treatment sequence comprising the steps of: (1) insolubiHzing the polymer by crosslin ng; (2) coating with a siHcone layer; and (3) crosslinking the siHcone layer. These membranes can be composite membrane further characterized by at least one of the following features (a), (b), (c) and (d), namely: (a) the ethylenically unsaturated nitriles are selected from acrylonitrile and substituted acrylonitriles; (b) prior to step (2), the crossHnked insolubiUze substrate obtained in step (1) has been treated with a pore protector in absence of curing agents and catalysts therefor; (c) the siHcone coating layer comprises at least one member selected from the group consisting of sUanol-terminated polydimethylsUoxane, other sUanol-terminated polysUoxanes, other hydroxy-terminated polysUoxanes, siHcones containing alkyl groups, sUicones containing aryl groups, and siHcones containing both alkyl and aryl groups; (d) the composite membrane sweUs to an extent of no more than about 10% when immersed in said solvents. The pore protector that may be present in such membranes comprises at least one member selected from the group consisting of sUanol-terminated polydimethylsiloxane, other silanol- terminated polysUoxanes, other hydroxy-terminated polysUoxanes, siHcones containing alkyl groups, sUicones containing aryl groups, and siHcones containing both alkyl and aryl groups. The substrate layer may be self-supporting or the substrate layer may be supported on another porous material. The insolubiHzing step comprises at least step (i) of the foUowing steps (i) and (H), namely: (i) treatment with at least one base selected from organic and inorganic bases; (u) subsequently to step (i), subjection of said substrate to heat-treatment, preferably at a temperature within the range of about 110-130°C. Either the siHcone coating or the pore protector, if present, or both, comprises at least one member selected from the group consisting of sUicones containing fluorine-substituted alkyl groups, siHcones contaiiiing fluorine-substituted aryl groups and siHcones containing both alkyl and aryl groups wherein either the alkyl groups or the aryl groups, or both the alkyl and aryl groups, are at least partly fluorine- substituted. Such membranes are composites having an membrane substrate which is a porous material, such as a microfiltration (MF), ultrafiltration (UF) or Reverse Osmosis (RO) membrane. The substrate can be made from a polymer, particularly a copolymer or a homopolymer of an ethylenicaUy unsaturated nitrile. The substrate is preferably treated with a pore protector (in absence of a curing agent) and then coated with a siHcone layer which is then crosslinked. The pore protector (which may be, for example, a hydroxy-terminated polysUoxane) serves the dual purposes of: (1) preventing the pores from coUapsing when the support is dried during the curing of the subsequently-appHed sflicone layer and (2) preventing passage of the subsequently-applied siHcone layer deeply into the pores and thus also preventing an undue reduction of the flux of the finished membrane. Treatment with the pore protector may be carried out, for example, by dipping the membrane substrate into a dilute solution of the pore protector in a low-boiling inert solvent, (e.g. a low boiling alcohol having 1 to 4 carbon atoms, such as methanol, ethanol, propanol or butanol). The final siHcone layer and the intermediate pore-protecting siHcone layer should desirably have a total thickness in the range of from 500 to 5000 A and, more preferably, in the range of from 1000 to 2000A. The above procedure Ulustrates a process for producing an opticaUy active aldehyde mixture having reduced metal content which comprises: (a) providing a crude hydroformylation reaction mixture, said reaction mixture comprising an opticaUy active aldehyde mixture and an opticaUy active metal-Hgand complex catalyst and (b) passing the reaction mixture through a membrane comprising a porous substrate layer and a siHcone layer to produce, as a permeate, an opticaUy active aldehyde mixture containing a reduced amount of the metal. Crystallization a. Solutions Once the requisite mixture of enantiomeric aldehydes has been provided, the next step of the process of this invention involves crystaUizing the mixture from a solution thereof so as to isolate the desired enantiomer in a purer form. Suitable solutions can be provided by using Hquid aldehydes or by melting solid aldehydes (when melt crystalHzation is employed). However, suitable solutions usually consist of the aldehydes dissolved in an appropriate solvent (e.g., in the solvent in which the first step of the process of this invention was conducted). Any solvent which will dissolve the aldehyde mixture may be used. Examples of suitable solvents are ketones (e.g., acetone), esters (e.g., ethyl acetate), hydrocarbons (e.g., toluene), nitrohydrocarbons (e.g., nitrobenzene) and ethers [e.g., tetrahydrofuran (THF) and glyme]. A mixture of two or more solvents can be employed to maximize the purity and yield of the desired aldehyde. The solution used may also contain materials other present in the crude reaction product of the aldehyde- forming reaction (e.g., catalyst, Hgand and heavies). Preferably, however, the solution consists essentiaUy of only the aldehyde mixture and the solvent. The concentration of the aldehyde mixture in the solvent solution wiU be limited by the solubiHty of the aldehyde mixture in the solvent. b. Crystallization Conditions In the process of this invention the solution containing the enantiomeric aldehyde mixture is maintained under conditions such that the solubiHty limit of the desired aldehyde is exceeded. Such conditions include addition of a non-solvent to the solution, removal of any solvent from the solution and, preferably, cooHng the solution (including vacuum cooling the solution). Combinations of these conditions canHoe used tcr effective desired crystallization. With respect to crystalHzation by using solvent removal, it should be noted that, if the pressure above the solution is fixed, then adding heat wiU increase solution temperature until the solution boUs. Upon continued addition of heat, solvent wiU evaporate and the solution wiU become saturated. At this point, the solution concentration wiU remain constant. (Gibbs Phase Rule) and continued heating wiU predpitate (crystaUize) solute (i.e., the desired aldehyde). Conversely, if the pressure above the saturated solution which exhibits an increase in solubility with increased temperature is slowly reduced, the temperature of the solution will decrease and cooling will cause predpitation (crystalHzation) of solute (i.e., the desired aldehyde). With respect to crystalHzation by using non-solvent (e.g., water) addition, it should be noted that adding a Hquid to the saturated solution that is misdble with the solvent but in which the solute has limited solubUity wUl cause the solute (i.e., the desired aldehyde) to predpitate (crystaUize). CrystalHzation using non- solvent addition is a preferred practice of this invention and is demonstrated in Example 10 below. Although the description of this invention appearing below relates primarily to crystalHzation by cooling, this invention encompasses any conditions for effecting the desired crystalHzation. c. Phase Diagrams This invention is appHcable to the separation of any enantiomeric aldehyde (first aldehyde) from an mixture containing that aldehyde and the corresponding enantiomeric aldehyde, provided the mixture is in the compositional region where only the first aldehyde crystalHzes on cooling of solution of the mixture. Suitable mixtures include mixtures of conglomerate aldehyde compounds ( lustrated by Fig. 2 which is discussed below) and mixtures of aldehydeεrthat can form racemic compounds (iUustrated by Fig. 3 which is discussed below). When aldehydes being separated are conglomerates, the crystalHzation phenomenon that occurs in the practice of this invention is generaUy governed by the factors Ulustrated in Fig. 2 which is a phase diagram of two substances, X and Y (e.g., enantiomer aldehydes). In Fig. 2, area (i.e., compositional region) I represents a unsaturated solution containing X and Y, area (i.e., compositional region) II corresponds to the coexistence of crystals of substance Y and the saturated solution containing ' X and Y, area (i.e., compositional region) III represents the coexistence of crystals of substance X and the saturated solution containing X and Y, and area (i.e., compositional region) IV corresponds to mixtures of crystals of substances X and Y. The curve separating areas (i.e., compositional regions) I and II is the solubiHty curve for substance Y, while the curve separating areas (i.e., compositional regions) I and III is the curve for phase equUibrium between soHd X and the corresponding solution containing X and Y. The curves intersect at point E, where soHd X, soHd Y and a solution with composition E, that is saturated with both X and Y are in equUibrium. Points t x and ty are the melting points of pure components X and Y, respectively. If an unsaturated solution containing X and Y (represented by point A in Fig. 2) is cooled, the composition of the solution does not change and the point representing the cooling solution therefore moves verticaUy downward on the phase diagram (Fig. 2). With continued cooling, this vertical line intersects the solubiHty curve at point B, lying on the boundary of the region corresponding to the separation of crystals of substance Y. On still further cooHng, crystals of only substance Y separate, the solution is depleted in component Y and hence the composition of the solution moves along the solubility curve from right to left. For example, on cooling the solution down to a temperature corresponding to point C, crystals of comp^sitiollT ^ aΕ ^teTiϊolhertiquor (melt θr ~ solutiori) with a composition corresponding to point D are in equilibrium in the weight ratio CD : CF. On a further decrease in temperature, the point representing the Hquid phase (solution) moves along the solubiHty curve towards point E. Finally, at a temperature corresponding to point G, crystals of H are in equUibrium with a solution of composition E. Solution E is saturated with both components, so that the crystals of both components wUl separate from a Hquid phase (solution) with a constant composition at constant temperature te on further removal of heat. Temperature t e is thus the lowest temperature at which crystals of a single component can still be obtained from the solution. For initial solution A, the weight ratio of the maximum obtainable amount of crystals of Y to mother liquor E is given by the ratio of segments EG : GH. Point E is called the eutectic point, temperature tβ is the eutectic temperature and the mixture of substances X and Y with composition corresponding to point E is a eutectic mixture. Fig. 3 is a melting point diagram (or phase diagram) of enantiomers that can form a racemic compound. The shape of such diagram can vary within rather large Hmits depending upon whether the racemic compound melting point is greater, lower, or equal to that of the enantiomers. In Fig. 3, tR represents a racemic compound having a melting point that is lower than tY (or t.χ), which is the melting point of the pure opticaUy active substance. The eutectic EY (or Ex consists of a mixture of crystalline Y (or X) and racemic compound R. If a solution of X and Y having composition A in Fig. 3 is cooled to B, pure crystalline Y wUl begin to form. As the solution of composition B is cooled further, the composition of the solution foUows the path from B to D to EY while continuing to form pure crystalline Y. Upon reaching solution composition Ey a mixture of crystalline pure Y and crystaUine racemic compound R forms thereby limiting possibUity of additional recovery of pure Y. SimUarly, crystals of only X can be obtained by cooling solutions in area V (i.e., compositional region V). If point K in Fig. 3 represents the initial solution composition, then cooling the solution to L initiates formation of racemic crystalline compound R. Upon Further cooling, the solution composition foUows the path L to N to EY whUe continuing to form crystalline racemic compound R. Upon reaching composition EY, a mixture of crystaUine pure Y and crystaUine racemic compound R forms. Thus, if K represents the initial solution composition, pure crystalline Y can not be obtained by cooling. Thus, Areas II and V in Fig. 3 illustrate compositional regions in which the process of this invention can be practiced to produce relatively pure X (area V) or relatively pure Y (area II). Although Fig. 2 and Fig. 3 have been disclosed above in terms of crystaUization achieved by cooHng, the phase relationships shown in Fig. 2 and Fig. 3 are also appHcable to crystallization achieved by any other means. d. Compositional Region InitiaUy, the appropriate concentration of the aldehydes in the solution (i.e., concentration in the region where only the desired enantiomer crystalHzes) can be achieved by controlling the above-described asymmetric syntheses, particularly by the proper selection of the chiral Hgand used in the syntheses. By way of Ulustration, the foUowing Hgands have resulted in aldehyde mixtures in the desired compositional region when used in rhodium-catalyzed asymmetric hydroformylation of 6-methoxy-2-vinylnaphthalene to produce the aldehyde precursor for S-naproxen (S-2-(6-methoxy-2- naphthyl)propionaldehyde): The results achieved with the above Hgands were as follows: Aldehyde Product Ligand b/n ratio* ee** A 100:1 78% B 70:1 76% C 50:1 79% D 65:1 82% E 60:1 83% F 75:1 82% * Ratio of branched isomer to normal isomer. ** Enantiomeric excess. The above hydroformylation reaction conditions were: 25°C, 130 psi, 1:1 H2/CO, 300 ppm Rh, 2:1 Hgand Rh ratio and an acetone solvent. The second step of the process of this invention (crystalHzation) is conducted using solutions containing non-eutectic aldehyde mixtures in the compositional region where only the desired aldehyde is obtained by crystalHzation. During crystalHzation by cooling, the relative concentration of the enantiomeric aldehydes, the uniformity of solution temperature, the cooling rate and the cooling temperature are controUed so that the concentration of the aldehydes remains in the region where only the desired enantiomer crystalHzes. Thus, with reference to Fig. 1, in order to crystaUize only component Y, the relative concentration of the enantiomers must be controUed to be to the right of eutectic concentration (E). During the crystalHzation (when the concentration of Y in the solution shifts to the left on the solubiHty curve toward the eutectic concentration, E), the appropriate concentration is maintained by stopping crystalHzation before the eutectic concentration and/or temperature are reached. The enantiomeric aldehyde mixtures useful in the process of this invention can have any composition other than the composition at which the mixture is eutectic (i.e., the mixtures are non-eutectic), provided the composition is in the region where only the desired aldehyde crystalHzes on cooling the mixture. The reason for the requirement of using non-eutectic mixtures is that unacceptably large amounts of the undesired enantiomer usuaUy crystallize from eutectic mixtures. e. Crystallization Temperature In the preferred practice of the process of this invention, solutions containing the enantiomeric aldehyde mixtures are cooled to effect crystalHzation of the desired enantiomer. Higher crystallization temperatures promote the formation of desirably larger crystals but increase the possibility of undesirable racemization. The temperature of the solution can be raised sHghtly after the crystals initiaUy form to a temperature just below the initial crystalHzation temperature and then the temperature can be lowered again. This technique causes the smaUer crystals to redissolve and the larger crystals to grow stiU larger with the result that better generation of the crystals from the solution is achieved. Crystallization temperature wiU effect both product purity and yield in that lower temperatures produce higher yields. Vacuum cooling is a preferred practice of this invention and is demonstrated in Example 11 below. f. Crystallization In Stages In the preferred practice of the process of this invention, the crystalHzation can, if desired, be conducted by cooling in stages. That is, the initial solution of the aldehyde mixture can cooled to a temperature at which the desired aldehyde crystaUizes and held at that temperature until crystalHzation is complete. Then the crystals can be filtered from the remaining solution to produce a filtrate and the filtrate can be again cooled to crystaUize additional amounts of the desired aldehyde. The cooling-crystaUization- filtration-cooling sequence can be repeated as often as desired, provided the eutectic composition and temperature are not reached. The advantage of operating in stages is increased yield of the desired aldehyde. It is desirable to remove some of the solvent between each cooling stage. g. Crystallization Apparatus In the practice of this invention, the crystalHzation of the desired enantiomeric aldehyde can be achieved using any convenient apparatus. The preferred apparatus is a faUing film crystaUizer such as is disclosed in U.S. Patent 3,621,664 and that apparatus contains vertical (usuaUy metalHc) wall surfaces which are cooled from the opposite wall surface. When the. Hquid phase (i.e., the solution of the aldehyde mixture) flows as a much smaUer stream-like film that is spread over the area of the waU, the separation is superior to that obtained when the Hquid phase fiUs the entire cross section of the means, such as a pipe, down which it flows, the wetted c cumference and the quantity of flow for the one case being equal to those of the other. The reason for this is that in the case of the film the flow is turbulent, whereas in the other case, for a given example, the flow has a Reynolds Number of 1600, indicating a laminar flow. The turbulent flow in the faUing film has a laminar boundary layer a few tenths of a millimeter thick where mass transfer occurs by molecular diffusion, whereas this boundary layer for a completely laminar flow is approximately ten millimeters thick. The equation for the actual distribution coeffident, reproduced in "Background of the Invention" in U.S. Patent 3,621,664, shows that a distribution coeffident approaching the best possible value is obtainable with film flow, when the crystalHzation rate is on the order of one centimeter per hour, as would be required in a large scale operations and, when the molecular diffusion coeffident in the Hquid phase is on the order of 10"^ centimeters^/second; whereas in the other case the distribution coeffident is dose to one, indicating virtually no separation. If good separation is wanted in the other case, the Reynolds Number must be raised, which necessitates a larger flow and greater power consumption, particularly with viscous liquids, rendering operation uneconomical. Good separation of the desired enantiomeric aldehyde during crystalHzation occurs in the apparatus of U.S. Patent 3,621,664 even in the laminar region, provided that the waves appearing on the film surface cause a mixing action. Here also the layer thickness is only a few tenths of a millimeter and separation is correspondingly good. The quantity of Hquid processed and the power consumed by the drculation pump are relatively little. The cooled vertical walls of the crystalHzer are, in a preferred embodiment, in the form of tube bundles having any desired number of vertical, paraUel tubes, the Hquid being introduced at the tops of the tubes by a distributor to flow down the tubes inner surfaces as a film, and the cooling medium filling the jacket surrounding the tubes. The lower end of the crystalHzer incorporates a tank for coUecting the Hquid phase. The desired aldehyde crystals usuaUy form on the inner surface of the falling film crystalHzer. The crystals are removed by dissolving the crystals in a solvent (e.g., acetone) at a temperature below the melting point of the desired crystals to avoid substantial racemization of the desired crystals. Two other arrangements of the apparatus of U.S. Patent 3,621,664 can be used for crystallization in accordance with this invention on an industrial scale. In one arrangement, crystalHzation occurs on the outer surfaces of a heat exchanger composed of a bundle of thin, paraUel tubes, with baffle plates causing a strong cross flow of the Hquid phase. In the other arrangement, the crystals form on the outer surface of a horizontal pipe grid, the Hquid phase flowing down over the grid. In both arrangements, the cross flow about the pipes causes a turbulence producing a general mixing action, the laminar boundary layer at each pipe being then very thin. Similar results are obtained with cooled or, for some appHcations, heated short fins or baffle plates positioned in the flow to give a pronounced cross flow. The separation in the preferred crystalHzation apparatus may be improved during crystalHzation by periodicaUy briefly heating (or cooling, in certain appHcations) the fluid phase before it enters the crystalHzer. This measure yields a smooth crystal surface and avoids dendritic or uneven crystal growth with the attendant undesirable trapping of mother Hquid within the crystal layer. CrystalHzation in the above-mentioned preferred crystaUization apparatus is conveniently carried out in a single apparatus in such a manner that single crystaUizations are cyclicaUy repeated, beginning with the step of the highest concentration of impurity or impurities and advancing to the step of the desired component in its purest form. The small amount of mother Hquor (i.e., solution of the aldehyde mixture) held on the surfaces of the crystalHzer only sHghtly contaminates the crystalHzation of the succeeding step and going from the "purest" step to the "least pure" step, when ending one cycle and starting another, does not influence the separation. The crystaUization process can be conducted in the preferred crystalHzation apparatus in an inert atmosphere. The crystals of the final step can be further purified by distillation or partial melting and the less pure separated substance returned to the final step. The surface on which crystalHzation occurs can be cooled by flowing a heat exchange medium, in the form of a film, over the opposite surface of the crystalHzer waU. This surface can be vertical, horizontal, or at any_angle therebetween. h. Product Purity The crystals of the desired enantiomeric aldehyde produced by the process of this invention contain considerably less of the other enantiomeric aldehyde than is contained the starting Hquid aldehyde mixture. However, some of the other aldehyde may be present in the crystals due to occlusion, incomplete draining or entrainment of the solution from which the crystals are formed. Thus, the process of this invention provides opticaUy active aldehydes having very high enantioselectivities and very high regioselectivities. With respect to enantioselectivity, enantiomeric excesses of preferably greater than 96%, and more preferably greater than 99%, can be obtained by the process of this invention. With respect to regioselectivity, branched/normal molar ratios of preferably greater than 100:1, more preferably greater than 200:1 and most preferably greater than 1000:1, can be obtained by the process of this invention. In addition, the desired aldehydes are relatively free of any residual metal catalyst (e.g., rhodium) used in the production of the starting aldehyde mixture, espedaUy when the above-described membrane separation is employed. Thus, if the initial aldehyde solution contains substantial amounts of metal catalyst (e.g., 300 parts per mflhon of rhodium), the desired aldehydes can contain less than 20 parts per million by weight of residual metal catalyst (e.g., rhodium) when crystalHzation without membrane separation is used. The desired aldehydes can contain less than 2 parts per million by weight of residual metal catalyst (e.g., rhodium) when membrane separation foUowed by crystalHzation is used. Derivatives and Utility The enriched, optically active aldehydes produced by the process of this invention can undergo further reaction(s) to afford desired derivatives thereof. Such derivatization reactions can be carried out in accordance with conventional procedures. IUustrative derivatization reactions indude, for example, oxidation to carboxyHc adds, reduction to alcohols, aldol condensation to alpha, beta- unsaturated compounds, reductive animation to amines, animation to imines and the like. This invention is not intended to be limited in any manner by the derivatization reactions. A preferred derivatization reaction involves oxidation of an opticaUy active aldehyde prepared by asymmetric hydroformylation to give the corresponding opticaUy active carboxylic add. A number of important pharmaceutical compounds can be prepared by such derivatization processes process including, but not limited to, S- naproxen, S-ibuprofen, S-ketoprofen, S-suprofen, S-flurbiprofen, S- indoprofen, S-tiaprofenic add and the like. Illustrative of such derivatization reactions include, for example, reactions that involve the foUowing reactant/ aldehyde intermediate/product combinations: Aldehyde Reactant Intermediate Product 2-vinyl-6-methoxy- S-2-(6-methoxy-2- S-naproxen naphthalene naphthyl)- propionaldehyde 2-vinyl-6-methoxy- S-2-(6-methoxy-2- S-naproxen naphthalene naphthyl)- sodium propionaldehyde p-isobutylstyrene S-2-(p-isobutylphenyl)- S-ibuprofen propionaldehyde 3-ethenylphenyl S-2-(3-benzoylphenyl)- S-ketoprofen phenyl ketone propionaldehyde 4-ethenylphenyl- S-2-(p-thienoylphenyl)- S-suprofen 2-thienylketone propionaldehyde 4-ethenyl-2-fluoro- S-2-(3-fluoro-4-phenyl)- S-flurbiprofen biphenyl phenylpropionaldehyde 4-(l,3-dihydro- 1-oxo- S-2-[4-(l,3-dihydro-l- S-indoprofen 2H-isoindol-2-yl)- oxo-2H-isoindol-2-yl)- styrene phenyl]propionaldehyde 2-ethenyl-5-benzoyl- S-2-(2-methyl- S-tiaprofenic thiophene acetaldehyde)-5-benzoyl- acid thiophene 3-ethenylphenyl S-2-(3-phenoxy)propion- S-fenoprofen phenyl ether aldehyde propenylbenzene S-2- S-phenetamid, S phenylbutyraldehyde butetamate phenyl vinyl ether S-2-phenoxypropional- phenetidllin dehyde vinyl chloride S-2-chloropropional- S-2-chloro- dehyde propionic add 2-vinyl-6-methoxy- S-2-(6-methoxy-2- S-naproxol naphthalene naphthyl)- propionaldehyde 5-(4-hydroxy)benzoyl- 5-(4-hydroxy)benzoyl- 1- ketorolac 3H-pyrrolizine formyl-2,3-dihydro- or derivative pyrroHzine 3-ethenylphenyl R-2-(3-benzoylphenyl)- R-ketoprofen phenyl ketone propionaldehyde 4-ethenyl-2-fluoro- R-2-(3-fluoro-4-phenyl)- R-flurbiprofen biphenyl phenylpropionaldehyde The opticaUy active derivatives of the products of the process of this invention have a wide range of utility that is well known and documented in the prior art, e.g. they are espedaUy useful as pharmaceuticals, flavors, fragrances, agricultural chemicals and the like. Ulus trative therapeutic appHcations, include, for example, non-steroidal anti-inflammatory drugs, ACE inhibitors, beta-blockers, analgesics, bronchodUators, spasmolytics, antihistimines, antibiotics, antitumor agents and the like. As used herein, the foUowing terms have the indicated meanings: Chiral - compounds which have a non-superimposable mirror image. Achiral - compounds which do not have a non- superimposable mirror image. Prochiral - compounds which have the potential to be converted to a chiral compound in a particular process. Chiral center- any structural feature of a compound that is a site of asymmetry. Racemic - a 50/50 mixture of two enantiomers of a chiral compound. Stereoisomers - compounds which have identical chemical constitution, but differ as regards the arrangement of the atoms or groups in space. Enantiomers - stereoisomers which are non- superimposable mirror images of one another. Stereoselective - a process which produces a particular stereoisomer in favor of others. Enantiomeric excess (ee) - a measure of the relative amounts of two enantiomers present in a product, ee may be calculated by the formula [amount of major enantiomer - amount of minor enantiomerjVE amount of major enantiomer + amount of minor enantiomer]. Optical activity - an indirect measurement of the relative amounts of stereoisomers present in a given product. Chiral compounds have the abUity to rotate plane polarized Hght. When one enantiomer is present in excess over the other, the mixture is optically active. Optically f.r.__γp. mixture- a mixture of stereoisomers which rotates plane polarized Hght due to an excess of one of the stereoisomers over the others. Optically pure compound- a single stereoisomer which rotates plane polarized Hght. Regioisomers - compounds which have the same molecular formula but differing in the connectivity of the atoms. Regioselective - a process which favors the production of a particular regioisomer over all others. IsoBHA chloridite - l,l'-biphenyl-3,3'-di-t- butyl-5,5'- dimethoxy-2,2'-diylchlorophosphite. (IsoBHA-P_9-2R.4R-pentanediol - A Hgand having the formula: The latter Hgand can be produced from Iso BHA chloridite by the process described in Example 1 of above-mentioned PCT Patent AppHcation 93/03839. The complete chemical name of this Hgand is (2R, 4R)-Di[2,2 , -(3,3'-di-tert-butyl-5,5 , -dimethoxy-l,l'- biphenyl)]-2,4-pentyl diphosphite. For purposes of this invention, the chemical elements are identified in accordance with the Periodic Table of the Elements, CAS version, Handbook of Chemistry and Physics, 67th Ed., 1986-87, inside cover. Also for purposes of this invention, the term "hydrocarbon" is contemplated to include aU compounds having at least one hydrogen and one carbon atom. In a broad aspect, the hydrocarbons include acycHc and cycHc, branched and unbranched, carbocyclic and heterocycHc, aromatic and nonaromatic organic compounds which can be substituted or unsubstituted. As used herein, the foUowing symbols have the indicated L liter mL milliliter wt% weight percent mL/min milHHters per minute ppm parts per million by weight ε grams psi pounds per square inch °C degrees centigrade b/n branched to normal isomer ratio CC cubic centimeter DSC Differential Scanning Calorimeter GC Gas Chromatographic HPLC High Performance Liquid Chromatography mm millimeter The foUowing Examples are provided to illustrate the process of this invention. roug rysta zat on n cetone A solution consisting of 6-methoxy-2-vinylnaphthalene (395 g), Iso(BHA-P)2-2R,4R-pentanediol (6.041 g), R__4(CO)i2 0.862 g) and acetone (1500 mL) was charged to a 1 gaUon reactor which was pressurized to 250 psi with 1:1 H2/CO. The reaction mixture was stirred at ambient temperature for four days to effect hydroformylation. The crude reaction product so produced was removed from the reactor and an aHquot removed to determine the composition of the product. GC analysis of the aliquot of the crude reaction product indicated that 98.8% of the olefin starting material had been converted to aldehydes and that a 95:1 ratio of 2-(6-methoxy-2- naph thyl)propionaldehyde to 3-(6-methoxy-2-naphthyl)- propionaldehyde had been obtained. Oxidation of the aldehydes in the aliquot followed by chiral High Performance Liquid Chromatography (HPLC) analysis of the resulting carboxylic adds indicated that an 81% ee of the desired S-aldehyde [i.e., S-2-(6-methoxy-2-naphthyl)- propionaldehyde] was produced. The above-mentioned oxidation and HPLC analysis were conducted as foUows: 3 mL of the crude reaction product was diluted in 50 mL of acetone and mixed with 0.3 g of potassium permanganate and 0.32 g of magnesium sulfate. The mixture so formed was stirred at room temperature for 30 minutes to effect oxidation of the aldehydes in the crude reaction product to the corresponding carboxylic adds. Then the acetone was removed under reduced pressure. The residue so produced was extracted three times with 50 mL of hot water and the three aqueous solutions so obtained were combined, filtered and washed with 50 mL of chloroform. The aqueous layer was then aάdified with HC1 to a pH of 2 at which time a white, solid predpitate formed. The precipitate was filtered, washed with water and dried to isolate the carboxyHc adds. The carboxyHc adds were analyzed by chiral HPLC on a CHIRACEL™ OD-H column which could separate the two enantiomers of the resulting 2-(6-methoxy-2-naphthyl)propionic add. The remainder of the crude reaction product was stored at -22°C overnight and during that time crystals formed. These crystals were filtered, washed with cold acetone and dried under vacuum to yield 111 g of off-white crystals and a first filtrate. Analysis of the crystals indicated that the b/n isomer ratio had been increased to >250:1. Oxidation of the aldehydes to carboxyHc adds and chiral HPLC of the resulting carboxylic adds indicated a 93% ee of the S-enantiomer had been obtained. The first filtrate was stored overnight at -22°C and additional crystals formed. These crystals were filtered, washed with cold acetone and dried under vacuum to yield a second filtrate and 70 g of white crystals with an b/n isomer ratio of 250:1 and a 93% ee of the S-enantiomer. The second filtrate was stored at -22°C overnight and again crystals formed. FUtration, washing and vacuum drying of these crystals resulted in isolation of 50 g of a crystalline aldehyde product having an b/n isomer ratio of 200:1 and an ee of 92% S- enantiomer. r ample 2 Imnroving Enantiomeric Purity of Aldehydes Through Crystallization in Ethyl Acetate A solution consisting of 6-methoxy-2-vinylnaphthalene (60 g), Iso(BHA-P)2-2R,4R-pentanediol (1.25 g), R__4 (CO)i2 (0.131 g) and ethyl acetate (180 g) was charged to a 300 mL reactor which was pressurized to 250 psi with 1:1 H2/CO. The reaction mixture so formed was stirred at ambient temperature for four days to effect hydroformylation. The crude reaction product was removed from the reactor and an aHquot removed to determine the composition of the product. GC analysis of the aliquot indicated that 99% of the olefin starting material had been converted to aldehydes and that a 59:1 ratio of 2-(6-methoxy-2-naphthyl)propionaldehyde to 3-(6-methoxy-2- naphthyl)propionaldehyde had been obtained. Oxidation of the aldehyde products foUowed by chiral HPLC analysis of the resulting carboxyHc adds indicated that an 80% ee of the desired S-aldehyde [i.e., S-2-(6-methoxy-2-naphthyl)propionaldehyde] was produced. The remainder of the crude reaction product was then stored at -22°C overnight, during which time crystals formed in the container. These crystals were filtered, washed with cold acetone and dried under vacuum to yield 32 g of off white crystals. Subsequent analysis of these crystals indicated that the b/n isomer ratio had been increased to >129:1. Oxidation of the crystalline aldehyde and chiral HPLC of the resulting carboxyHc add indicated a 92% ee of the S-enantiomer had been obtained. Example 3 Membrane Separation of An Aldehyde from Acetone Solution A. A crude hydroformylation reaction product simUar to the crude reaction product produced in Example 1 above was processed through a membrane to remove the rhodium and Hgand. The crude reaction product contained 2-(6-methoxy-2- naphthyDpropionaldehyde (30 wt%) dissolved in acetone (70 wt%) . The crude reaction product also contained rhodium (263.3 ppm) and ligand. The membrane and associated equipment is shown in Fig. 4. The membrane was arranged and used as follows: Three-2 inch circles were cut from an 8 inch xll inch sheet of MPF-50 membranes (Lot #021192, code 5107) which are sold by Membrane Products Kiryat Weizmann Ltd. and which are beHeved to be within the scope of above-mentioned European Patent AppHcation 0 532,199 Al. These drcles were placed into three Osmonics membrane holders. The crude reaction product (feed) was placed into a 2L Hoke cylinder under nitrogen. The feed was pumped to 500 psi at a flow rate of about 380 mL/min. The feed flowed through a 60 micron filter and then was split into three streams which went to the membranes. Flowmeters were used to ensure that the flow was split equally to the holders. The permeate from the membranes was combined and collected under nitrogen. The raffinate flowed to a back pressure regulator and was then returned to the Hoke cylinder. About 1500 g of the crude reaction product was permeated and the rhodium content of the resulting first permeate was about 69.4 ppm. The membrane and equipment were washed with acetone and the acetone was discarded. The above-described membrane separation was repeated on the 1500 g of the first permeate (which contained 69.4 ppm rhodium) and 1000 g of a solution (containing 19.2 ppm rhodium) was separated as a second permeate. The composition of the second permeate was 80% acetone and 20% soHds. The b/n isomer ratio of the soHds was 64:1 and it contained 1.4% normal isomer, 9.9% R- isomer, and 88.7% S-isomer [i.e., S-2-(6-methoxy-2-naphthyl)- propionaldehyde]. The enantiomeric excess (ee) of the crystalline solids was 80.7%. The second permeate so obtained was then concentrated and crystaUized as described below. A portion of the second permeate produced as described above was concentrated by evaporating acetone at 18°C and 25 inches of mercury pressure to produce a concentrated solution containing 70% acetone and 30% soHds. The concentrate so obtained was charged into the crystalHzer shown in Fig. 5. The crystalHzer consisted of a jacketed, 250 cc vertical cylinder (A) fitted with a stirrer (B) and an internal filter (C). CrystalHzation was initiated by cooling the jacket to -14°C thus cooling the contents of the cylinder to near -14°C. In order to dissolve the smaU crystals that formed on the inner surface of the cylinder and to enhance crystal size, the crystalHzer was reheated to 3°C and again cooled to -14°C using cooler (D). This procedure was repeated three times. Since the internal filter (C) clogged, the soHd crystals formed in the cylinder and Hquid were removed from the crystaUizer and separated in a laboratory vacuum filter. The resulting filter cake was washed with one part by weight of cold acetone (0°C) per two parts (by weight) of wet solids (filter cake). The resultant crystalline filter cake contained 13% acetone and 87% crystalline solids and had a b/n isomer ratio of 386:1. The soHds contained 0.3 normal isomer, 2.4% R-isomer and 97.3% S-isomer. The enantiomeric excess of the soHds was 95.2%. Scanning Electron Microscope (SEM) photos indicated that soHd particles were uniform and about 100 microns in size. B. The concentration and crystaUization procedure of A above was repeated with another portion of the second permeate obtained in the above-described membrane separation and the crystals produced had a b/n isomer ratio of 446:1 and contained of 0.2% normal isomer, 2.7% R-isomer, and 97.1% S-isomer. The ee of the crystals was 94.6%. C. The wet filter cakes produced via the procedures of A and B above were combined and dissolved in two parts by weight of acetone per part by weight of the combined wet filter cake. The solution so obtained was crystaUized using the crystalHzation procedure of A above, separated and washed per the procedure of A above. The resultant crystals had a b/n isomer ratio of 921:1 and contained 0.1 normal isomer, 1.3% R-isomer, and 98.6% S-isomer. The ee of the crystals was 97.4%. D. The wet crystaUine filter cake produced by procedure of C above was dissolved in two parts (by weight) of acetone per part of the combined wet cake and crystaUized using the crystalHzation procedure of A above, separated and washed according to the procedure of A above. The final crystals so obtained had a b/n isomer ratio of 1836:1. The crystal contained 0.05% normal isomer, .6% R-isomer, 99.35% S-isomer and 4 ppm rhodium. The ee of the crystals was 98.8%. The melting point of the crystals was 72.5°C deteπnined in a Differential Scanning Calorimeter (DSC). _f-τrιpl 4 Refining An Aldehyde from Ethyl Acetate Solution A . A crude hydroformylation reaction product was used that was similar to the crude reaction product produced in Example 2 above and that was composed of 62.9% ethyl acetate and 37.1% soHds containing 2-(6-methoxy-2-naphthyl)propionaldehyde. The soHds had a b/n of 42:1 were composed of 2.3% normal isomer, 11.7% R-isomer and 86% S-isomer [i.e., S-2-(6-methoxy-2-naphthyl)- propionaldehyde] and had an ee of 76%. The crude reaction product was crystaUized as foUows: B. Seven successive 250 cc charges of the crude reaction product were cooled to -7°C in the crystaUizer used in Example 3 above (see Fig. 5). The crystals and Hquid resulting from the crystaUization were separated on an external vacuum filter and the crystals were washed with 0.5 parts of ethyl acetate per part of wet cake. The resultant composite cake from the seven crystaUizations contained 24% ethyl acetate and 76% crystalline soHds. The b/n isomer ratio of the crystalline soHds was 123:1 and the solids contained .8% normal isomer, 6.0% R-isomer, and 93.2% S- isomer. The ee of the crystaUine soHds was 87.9%. C . The wet filter cake from step B. above was dissolved in two parts by weight of ethyl acetate per part (by weight) of wet filter cake. The solution was cooled to -13°C in the laboratory crystalHzer (Fig. 5). The contents of the crystaUizer were then reheated to 3°C and again cooled to -13C. This cool-reheat cycle was repeated two times to enhance the crystal size. The soHd-Hquid mixture so produced was separated in an external vacuum filter and the wet filter cake 50 produced was washed with 0.5 parts of cold (-10°C) ethyl acetate per part of wet filter cake. The resultant cake contained 25% ethyl acetate and 75% crystalline soHds. The crystaUine soHds had a b/n isomer ratio of 483:1 and had, a normal isomer content of .2%, a R-isomer content of 1.6% and a S-isomer content of 98.2%. The ee of the crystaUine solids was 96.8%. Example 5 Refining of An Aldehyde from Acetone Solution in a Falling Film CrystaUizer Crude hydroformylation reaction product that was similar to the crude reaction product produced in Example 1 above and that contained 70% acetone and 30% soHds was refined in a laboratory falling film crystalHzer. The soHds in the crude reaction product had a b/n isomer ratio of 69:1 and the soHds composition was 1.4% normal isomer, 8.9% R-isomer, and 89.7% S-isomer [i.e., S-2-(6- methoxy-2-r_aphthyl)propionaldehyde]. The enantiomeric excess of the soHds was 81.9%. The crude reaction product was concentrated by evaporating 30% by weight of the solution. The resulting concentrate consisted of 57% acetone and 43% soHds. This was crystaUized in a laboratory falling film crystalHzer by the foUowing procedure. The crystaUizer used is shown in Fig. 6 and consisted of a kettle (A), a jacketed column (B) {the column was a one meter long jacketed vertical tube having a one inch diameter internal opening} and (D) means for pumping (i.e., circulating) Hquid from the kettle to the film device (C) at the top of the faUing film crystalHzer. The jacket of the crystalHzer was affixed to a supply of coolant (E) which flowed co-current with the faUing film. That is, both the falling film and the coolant in the jacket flowed downward in a co-current fashion. The crystalHzer shown in Fig. 6 is similar in prindple of operation to those described in above-mentioned U.S. Patent 3,621,664. Two thousand milHHters of the concentrate produced as described above were charged to the kettle (A) of the falling film crystaUizer (Fig. 6). The concentrate in the kettle was circulated briefly down through the column (B) to wet the inside waUs and then circulation was discontinued. Since the waUs of the column were maintained at -20°C by drculating coolant, a thin frosting of solids quickly formed on the inner walls of the column. The flow through the faUing film crystalHzer was resumed depositing crystals on the inside of column wall. After the kettle temperature was reduced to -16°C, the redrculation flow was stopped. During the cooling, a slight amount of heat was added to the kettle by a heating mantle (F) to prevent crystaUization in the kettle. To compensate for this hea ting, the recirculating Hquid was cooled slightly by drculating coolant from bath (G) to coolers (H). After crystalHzation was complete, the residual Hquid in the kettle was emptied and the solids inside the crystaUizer walls were washed with 50 cc of wash Hquid that was added from the top of the column and this wash Hquid was discarded. The composition of the kettle residue was 61% acetone and 39% soHds. The soHds in the kettle had a b/n isomer ratio of 60:1 and contained 1.6% normal isomer, 12.8% R-isomer and 85.6% S- isomer. The ee of the kettle soHds was 74.0%. 600 CC of reagant grade acetone was added to the kettle and drculated to the falling film device at 20°C and then down the inside waU of the column to dissolve the soHds adhering to the inside of the column. This was a very quick and effident technique for recovering adhering soHds and is a unique method for recovery of soHds from the falling film crystaUizer. In the prior art, the internal film of crystals in such crys talHzers is normaUy melted (see above- mentioned U.S. Patent 3,621,664). However, this invention is designed to increase the amount of the desired enantiomeric aldehyde (in this Example, the S-isomer) and melting is not feasible since the S-isomer wiU quickly racemize at its melting point (72.5°C) and so the ee of the crystals wiU deteriorate. The acetone solution recovered from the column waU contained 78% acetone and 22% crystaUine soHds. The crystaUine soHds had a b/n isomer ratio of 111:1 and contained 0.9% normal isomer, 6.9% R-isomer and 92.2% S-isomer. The crystalHne soHds ee was 86.1%. Example 6 Refining of An Aldehyde from Acetone Solution Utilizing Cooling Crystallization Three 2 inch circles from an 8.5 inch x 11 inch sheet of MPF-50 membranes (LOT #021192 code 5102). These were placed into three Osmonics membrane holders. Feed was placed into a 2L Hoke cylinder under nitrogen in equipment arranged as shown in Fig. 4. The feed was pumped to 500 psi at a flow rate of about 380 mL min. The feed flowed through a 60 micron filter and then was spHt into three streams which went to the membranes. Flowmeters were used to ensure that the flow was spHt equaUy. The permeate from the membranes was combined and coUected under nitrogen. The raffinate flowed to a back pressure regulator and then was returned to the Hoke cylinder. The feed was a 4 L batch of a crude hydroformylation reaction product containing 2-(6-methoxy-2-naphthyl)- propionaldehydes (30 wt%) in acetone (70 wt%). The mixture also contained rhodium (389.3 ppm) and Iso(BHA-P)2-2R,4R-pentanediol. About 3325 g of this solution was permeated through the membrane and the resulting permeate solution had a rhodium content about 36.3 ppm. The system was emptied, cleaned with acetone and the waste discarded. The 3325 g of the permeate solution containing 36.3 ppm rhodium was placed back into the Hoke cylinder and about 1439 g of this solution was again permeated through the membrane. The resulting permeate solution contained about 5.6 ppm rhodium. The 1439 g of the solution containing 5.6 ppm rhodium was placed back into the Hoke cylinder and passed back through the membrane for the third time. About 935 g of this solution was permeated through the membrane and the resulting permeate had about 1.2 ppm rhodium. This permeate was then used as a feed for the crystallization process described below. Recovery and refining of S-2-(6-methoxy-2-naphthyl)- propionaldehyde aldehyde from the permeate obtained as described above was accompHshed by the sequence of operations depicted in Fig. 11. In summary, the permeate feed solution was batch crystaUized by cooling to - 10°C. The slurry so obtained was filtered to remove crystals and the crystals were washed with one half gram of acetone per gram of wet soHds. The filtrate and was were combined and the solution concentrated to 40 percent soHds by evaporating acetone. The crystalHzation, filtration and washing was repeated on this concentrated solution. The crystals from this second stage were combined with crystals from the first crystalHzation and dissolved in one and one half parts by weight of acetone per part of wet soHds. This solution was processed in the same manner as the original permeate feed solution. The soHds that were recovered and washed from both crystalHzation stages were again combined and dissolved in acetone. The final recrystaUization was also conducted in the manner as described above in this Example. The refined crystaUine solids from this last stage represented the final product (i.e., S-2-(6- methoxy-2-naphthyl)propionaldehyde). The final ee was 96.8. The yield of S-2-(6-methoxy-2-naphthyl)propionaldehyde as a fraction of that supplied in the feed was 26.8 percent. Example 7 A. Naproxen Aldehyde Melting Point Diagram Fig. 7 is a melting point diagram for naproxen aldehyde enantiomers [i.e., R- and S-2-(6-methoxy-2-naphthyl)- propionaldehyde]. The liquidus curves in Fig. 7 were calculated using the Schroder-Van Laar equation [see Jacques, J., A. Collet, and S.H. Wilen, "Enantiomers,Racemates, and Resolutions"; Kriegar (1991) p. 46] using 74°C as the melting point of the pure isomers and 5630.4 calories per gram mole for the enthalpy of fusion. The assumptions in the Schroder-Van Laar equation include immisdbility of enantiomers in the solid state and ideality of the enantiomer mixture in the Hquid state. Experimental data was obtained using the crystalHzer shown in Fig. 5 and is indicated in Fig. 7 as circles. Samples were obtained during crystallization tests in acetone solutions. The solid samples were removed from the slurry by filtration. The samples were then slowly heated in a Perkin/Elmer DSC7 to obtain the melting point. The data on Fig. 7 are tabulated on Table 1. The melting point of pure S enantiomer (S-2-(6-methoxy- 2-naphthyl)propionaldehyde) is discernible. It is difficult to develop a complete Hquidus curve for a variety of reasons. A problem with melting point determination of such solid samples is that N isomer is present in suffiάent concentration to depress the mixture melting point. Table 1 Naproxen Aldehvde Melting Point Data Sample Comnosition Melting Point. °C _ £ R %N 98.2 1.7 0.1 73.5 94.3 5.0 0.7 66.1 98.2 1.6 0.2 72.7 94.8 4.7 0.5 69.4 87.4 10.8 1.8 63.7 95.5 4.0 0.5 72.5 88.1 8.7 3.2 57.2 92.3 7.0 0.7 66.9 B. Naproxen Aldehyde Solubility Fig. 8 summarizes solubUity data for soHds in acetone solvent. The data were obtained by visuaUy obtaining a "cloud" point for a solution of known composition by slowly cooling the solution. After obtaining a "cloud" point the solution was slowly heated until a "clear" point was observed. The "clear" point represents the saturation temperature of the solution and the "cloud" point the temperature at which massive spontaneous nucleation occurs. The data are shown in Table 2. Naproxen aldehydes [i.e., R- and S-2-(6-methoxy-2- naphthyl)propionaldehyde] are very soluble in acetone. The solubiHty of these aldehydes is very sensitive to temperature and a high degree of solution subcooling is required to nucleate the solution. Table 2 Naproxen Aldehyde Solubility Data in Acetone Solids Ratio Clear Cloud (wt%) Solids/Liαuid Point. °C Point. °C 29.0 0.41 6 -17 35.3 0.55 15 -9 30.0 0.43 11 -6 22.0 0.28 1 -15 47.0 0.89 25 5 C. Naproxen Aldehyde Distribution Coeffidents Fig. 9 and Fig. 10 summarize distribution coefficients or "K" factors for "Naproxen aldehydes" [i.e., R- and S-2-(6-methoxy-2- naphthyl)propionaldehyde] crystallized from acetone solutions. The data are obtained from a variety of experimental runs over a wide range of Hquid compositions. κ A = c A C A wherein: s CA = aldehyde concentration in soHd L CA = aldehyde concentration in Hquid If K is greater than 1, then the crystaUized soHds are enhanced in that component. If K is less than 1 then the crystaUized solids are depleted of the particular component. Experimental data shown that the distribution coeffident for S-aldehyde, (Ks), is greater than 1 for the solution concentration range tested. Experimental evidence shows that S- aldehyde is enhanced by crystalHzation from acetone solutions ranging from 54 to 98.6% S isomer (i.e., S-2-(6-methoxy-2- naphthyDpropionaldehyde). Also there is experimental evidence that verifies that R and N isomers are preferentially excluded via crystallization in the S solution range between 54 and 98.6%. There is some evidence that the S and R isomers form a solid solution in the high purity S isomer range. Although the Kg factor is greater than one, the stage effidency is only 50% at the high purity end versus 80% or better in the middle range. In the low S isomer region, the 54% S isomer residue Hquid soHdified after concentrating and cooling. It may be possible to squeeze a Httle more S isomer out of solution but 50% S is probably a lower limit on residue concentration via crystalHzation technology. Fig. 9 also indudes data from a single faUing film crystalHzer experiment conducted in the crystalHzer shown in Fig. 6. ^ Suffident data were generated to show that the falling film crystalHzation was effective in upgrading the ee of the desired aldehyde. Distribution coeffidents for falling film crystalHzation using the crystalHzer of Fig. 6 are similar in magnitude to results obtained using the crystalHzer of Fig. 5. Example 8 Recovery of S-Naproxen Aldehyde from Acetone Solution A crude reaction product of an asymmetric hydroformylation reaction was produced with low ee (62%) to experimentally investigate the quaHty of S-naproxen aldehyde [i.e., S- 2-(6-methoxy-2-naphthyl)propionaldehyde] that can be recovered from solutions with high concentrations of corresponding isomeric R- and N-aldehydes. Using the cooling crystalHzation procedure described in Example 3 above (i.e., the solution is cooled to -15°C, reheated to 0°C and this technique repeated three times before a final cool down to minus 15), a feed solution containing 77.6% S-isomer, 18.2% R- isomer and 4.2% N-isomer and having an enantiomeric excess (ee) of 62% was processed. The resulting crystals were recovered on a vacuum filter and washed with cold acetone. The composition of the crystals was 95.5% S-isomer, 4.0% R-isomer, and 0.5% N-isomer giving an enantiomeric excess of 92%. The filtrate recovered from the crystaUization procedure described above in this Example and having a solids concentration of 65.5% S-isomer, 26.8% R-isomer and 7.7% N-isomer was concentrated to 53% soHds by evaporating acetone under vacuum. The concentrate so obtained was crystaUized using the crystalHzation procedure described above in this Example. The composition of the crystalline soHds obtained by the latter crystalHzation was 92.3% S-isomer, 7.0% R-isomer and 0.7% N- isomer. The enantiomeric excess of those solids was 85.9%. The composition of the solids in the final filtrate was 54.1% S-isomer, 37.6% R-isomer and 8.3% N-isomer. JSxample 9 Improving Enantiomeric Purity of 2-.p-Isobutylphenyl)propionaldehvde Through Melt Crystallization A solution was prepared consisting of p-isobutylstyrene (100.2 g), Iso(BHA-P)2-2R,4R-pentanediol (0.85 g), and Rh4(CO)i2 (0.091 g). 100 mL of the mixture so formed was charged to a 300 mL reactor which was pressurized with 1:1 H2/CO. The mixture was stirred at 25°C for 46 hours at 130 psi to effect hydroformylation. The crude reaction product was removed from the reactor and an aHquot removed to determine the composition of the product. GC analysis on a beta-cyclodextrin chiral capUlary column (Cyclodex-B™) indicated that 99.4% of the olefin starting material had been converted to aldehydes and that a 42:1 ratio of 2-(p- isobutylphenyl)propionaldehyde to 3-(p-isobutylphenyl)propion- aldehyde had been obtained. Oxidation of the aldehyde products followed by chiral gas chromatography of the resulting carboxyHc adds indicated that an 85±5 % ee of the desired S-aldehyde [i.e., S-2- (p-isobutylphenyl)propionaldehyde] was produced. A portion (25 mL, 23.54 g) of the crude product was flash distilled to separate the products from the catalyst. The first cut (12.4 g) was obtained at 89-92°C head temperature at a pressure of 1 mm of Hg. A second cut (9.4 g) was obtained at 83-4°C at 0.6 m of Hg, and a small amount was left as residue. The second cut was partially frozen and some Hquid (3.27 g) was withdrawn, first with a pipet and then a fritted glass filter stick with the Hquid at -12 to -17°C. Oxidation of portions of the Hquid and crystals with sodium chlorite followed by chiral gas chromatography of the resulting carboxyHc adds indicated 92±1 and 75±2 % ee for the S- aldehyde in the crystals and and Hquid respectively. The ratios of the concentrations of other impurities in Hquid to their concentrations in the crystals averaged 2.2 and the b/n ratio in the crystals was 54:1. The oxidation with sodium chlorite referred to above was conducted as foUows: A mixture of 0.28 gram of aldehyde and 2.0 mL of distilled water was cooled to 0°C and stirred. Aqueous sodium sulfamate (3 L of 1 M, adjusted to pH 5 with phosphoric add) and sodium chlorite (0.61 mL of 20%) solutions were added. After 15 minutes, the cooling bath was removed and the solution was stirred for an additional 15 minutes as it was allowed to warm to room temperature. The pH was adjusted to 9.5 with 0.5 mL of 1 N sodium hydroxide and the material rinsed with water into a separatory funnel. The solution was shaken with added dichloromethane (10 mL) to extract neutral compounds. The aqueous layer was separated and addified to pH<2 with concentrated hydrochloric add. The cloudy mixture that formed was extracted with 20 mL of dichloromethane, toluene was added as an internal standard, and a small sample was taken to determine the yields of branched and normal adds by gas chromatography. The remaining solution was dried over anhydrous magnesium sulfate and filtered. The dichloromethane was removed with a rotary evaporator under vacuum (-150 mm Hg) with the bath at 60°C. The residue (0.02 g)was dissolved in toluene and analyzed by chiral gas chromatography. Example 10 Refining of An Aldehyde from Acetone Solution Utilizing Cooling Crystallization and Non-Solvent Addition Crude hydroformylation reaction product (47 g) that was similar to the crude reaction product produced in Example 1 above and that contained 70.5 g of acetone was partiaUy refined in a laboratory crystalHzer in a manner similar to Example 6. The solids in the partially refined reaction product had 97.65% S-isomer [i.e., S- 2-(6-methoxy-2-naphthyl)propionaldehyde]. The partiaUy refined product was further predpitated by adding non-solvent (water) at the final crystaUizer condition. The quantity of water added was 0.5 CC per CC of crystaUized slurry. The quaUty of the S-isomer recovered after vacuum filtration and washing with 150 CC of water was 97.87%. The quantity of material recovered was 40 g. By repeating this procedure four times, product quaUty increased to 99.10% ( 98.2% ee) with a recovery of 28 g. Example 11 Refining of An Aldehyde from Acetone Solution Utilizing Va_....m Cooling Crude hydroformylation reaction product (666 g) that was similar to the crude reaction product produced in Example 1 above and that contained 40% acetone and 60% soHds was added to a crystalHzation apparatus designed to provide vacuum cooling as described below. The soHds had a b/n ratio (2-(6-methoxy-2- naphthyl)propionaldehyde to 3-(6-methoxy-2-naphthyl)- propionaldehyde) of 82.76:1 and a 76% ee of the S-isomer [i.e., S-2-(6- methoxy-2-naphthyl)propionaldehyde]. The apparatus consisted of a jacketed one Hter kettle equipped with stirrer, condenser and vacuum pump. The solution was cooled to 5°C, where crystals formed, and then to 0°C by slowly reduάng the vacuum to a final reading of 50 mm absolute. The contents of the kettle were maintained at 0°C for 15 minutes and then heated to 8°C by increasing system pressure to 150 mm and warming the kettle jacket to 10°C to heat the contents. Conditions in the kettle were maintained at 8°C for 10 minutes, vacuum was again reduced to 50 mm and the kettle temperature reduced to 0°C. This heat back technique was employed to dissolve fine crystals and re-deposit the supersaturation onto existing crystals thereby enhancing the crystal size. After maintaining kettle temperature at 0°C for 10 minutes the contents were separated in a laboratory centrifugal filter and washed with cold acetone. About 60 g of dry soHds were recovered with a b/n ratio of 440:1 and an ee of 92.3%. Although the invention has been Ulustrated by certain of the preceding examples, it is not to be construed as being limited thereby; but rather, the invention encompasses the generic area as hereinbefore disclosed. Various modifications and embodiments can be made without departing from the spirit and scope thereof.

Claims: Claims 1. A process for producing an optically active aldehyde (first aldehyde) containing a reduced amount of the corresponding enantiomeric aldehyde (second aldehyde) which process comprises: (1) providing an initial solution containing a non- eutectic mixture of the first aldehyde and the second aldehyde, which mixture has a composition in the compositional region where only the first aldehyde crystallizes when its solubility limit in the solution is exceeded, and (2) maintaining the solution at a temperature above the eutectic temperature of the mixture and under conditions such that the solubiHty limit of the first aldehyde is exceeded so as to form a crystalline first aldehyde containing relatively less of the second aldehyde than was present in the initial solution. 2. A process as claimed in claim 1 wherein the first aldehyde is S-2-(6-methoxy-2-naphthyl)propionaldehyde and the second aldehyde is R-2-(6-methoxy-2-naphthyl)propionaldehyde. 3. A process as claimed in claim 1 wherein the first aldehyde is S-2-(p-isobutylphenyl)propionaldehyde and the second aldehyde is R-2-(p-isobutylphenyl)propionaldehyde. 4. A process as claimed in claim 1 wherein step (2) involves cooHng the initial solution in a falling film crystaUizer to achieve crystaUization of the first aldehyde on a surface of the crystaUizer. 5. A process as claimed in claim 4 in which the first aldehyde crystallizes on a surface of the crystaUizer and is dissolved by a solvent at a temperature below the melting point of the first aldehyde to avoid substantial racemization of the first aldehyde. 6. A process as claimed in claim 1 wherein step (2) is conducted by cooHng the initial solution in stages wherein (a) the solution (depleted solution) resulting from crystalHzation in a first stage is separated from the crystals formed in the first stage, (b) the depleted solution so formed is cooled in a second stage to form additional crystals and (c) additional stages are conducted per (a) and (b) until the desired degree of crystalHzation is achieved. 7. The process of claim 1 in which the optically active product has an enantiomeric excess of greater than 96%. 8. The process of claim 1 wherein the regio¬ selectivity of the product, in terms of its branched to normal isomer ratio, is greater than 1000:1. 9. A process as claimed in claim 1 wherein step (1) comprises contacting a prochiral or chiral compound in the presence of an optically active metal-Hgand complex catalyst to produce an optically active aldehyde mixture, said optically active metal-Hgand complex catalyst comprising a metal complexed with an optically active Hgand having the formula: wherein each W is the same or different and is phosphorus, arsenic or antimony, each X is the same or different and is oxygen, nitrogen or a covalent bond linking W and Y, Y is a substituted or unsubstituted hydrocarbon residue, each Z is the same or different and is a substituted or unsubstituted hydrocarbon residue or the Z substituents bonded to W may be bridged together to form a substituted or unsubstituted cyclic hydrocarbon residue, and m is a value equal to the free valence of Y, provided at least one of Y and Z is optically active. 10. The process of claim 9 which comprises isomerization, aldol condensation or hydroformylation. 11. A process as claimed in claim 9 wherein step (1) comprises a hydroformylation process which comprises contacting a prochiral or chiral olefinically unsaturated organic compound with carbon monoxide and hydrogen in the presence of an opticaUy active rhodium-ligand complex catalyst to produce an opticaUy active product, said optically active metal-Hgand complex catalyst comprising a metal complexed with an optically active Hgand having the formula wherein each W is the same or different and is phosphorus, arsenic or antimony, each X is the same or different and is oxygen, nitrogen or a covalent bond linking W and Y, Y is a substituted or unsubstituted hydrocarbon residue, each Z is the same or different and is a substituted or unsubstituted hydrocarbon residue or the Z substituents bonded to W may be bridged together to form a substituted or unsubstituted cyclic hydrocarbon residue, and m is a value equal to the free valence of Y, provided at least one of Y and Z is optically active; with the provisos that when each W is phosphorus and each X is a covalent bond, then the Z substituents cannot all be hydrocarbon residues having a carbon atom directly bonded to phosphorus, and when Y is a substituted 2 carbon aliphatic chain and m is a value of 2 and both W substituents are phosphorus and one X substituent is oxygen and the other X substituent is nitrogen, then the Z substituents cannot aU be phenyl, and when Y is a substituted tetrahydropyran and m is a value of 2 and both W substituents are phosphorus and the X substituents are both oxygen, then the Z substituents cannot aU be aryl. 12. A process as claimed in claim 11 wherein the Hgand is (2R,4R)-di[2,2'-(3,3 , -di-tert-butyl-5,5 , -dimethoxy- 1,1'biphenyl)] 2,4-pentyl diphosphite. 13. The process of claim 11 in which the opticaUy active metal-Hgand complex catalyst comprises a metal selected from a Group VIII, Group IB and Group VIB metal complexed with an optically active Hgand having the formula selected from wherein W, Y, Z and m are as defined in claim 1 and Y" is the same or different and is hydrogen or a substituted or unsubstituted hydrocarbon residue. 14. The process of claim 11 in which the olefinicaUy unsaturated organic compound is p-isobutylstyrene, 2-vinyl-6- methoxynaphthylene, 3-ethenylphenyl phenyl ketone, 4- ethenylphenyl-2-thienylketone, 4-ethenyl-2- fluorobiphenyl, 4-(l,3- dihydro-l-oxo-2H-isoindol- 2-yl)styrene, 2-ethenyl-5-benzoylthiophene, 3-ethenylphenyl phenyl ether, propenylbenzene, isobutyl-4- propenylbenzene, phenyl vinyl ether or vinyl chloride. 15. The process of claim 11 in which the product of the hydroformylation contains, as the first aldehyde, S-2-(p-isobutyl- phenyDpropionaldehyde, S-2-(6-methoxy-2-naphthyl)- propionaldehyde, S-2-(3-benzoylphenyl)propionaldehyde, S-2-(p- thienoylphenyD-propionaldehyde, S-2-(3-fluoro-4-phenyl)- phenylpropionaldehyde, S-2-[4-(l,3-dihydro-l-oxo-2H-isoindol-2- yDphenyl]- propionaldehyde, S-2-(2-methylacetaldehyde)- 5- benzoylthiophene, S-2-(3-phenoxy)-propionaldehyde, S-2- phenylbutyraldehyde, S-2-(4-isobutylphenyl)- butyraldehyde, S-2- phenoxypropionaldehyde, S-2-chloropropion-aldehyde, R-2-(3- benzoylphenyl)propionaldehyde or R-2-(3-fluoro-4-phenyl)- phenylpropionaldehyde. 16. The process of claim 1 wherein step (2) is conducted by addition of a non-solvent to the solution, removal of any solvent from the solution, cooHng the solution, vacuum cooling the solution or combinations thereof.

Inventors: BARNER BRUCE ARMIN, BRIGGS JOHN ROBERT, KURLAND JONATHAN JOSHUA, MOYERS CHARLES GUTHRIE JR, BARNER, BRUCE, ARMIN, BRIGGS, JOHN, ROBERT, KURLAND, JONATHAN, JOSHUA, MOYERS, CHARLES, GUTHRIE, JR.
Applicants: BARNER BRUCE ARMIN, BRIGGS JOHN ROBERT, KURLAND JONATHAN JOSHUA, MOYERS CHARLES GUTHRIE JR, UNION CARBIDE CHEM PLASTIC, BARNER, BRUCE, ARMIN, BRIGGS, JOHN, ROBERT, KURLAND, JONATHAN, JOSHUA, MOYERS, CHARLES, GUTHRIE, JR., UNION CARBIDE CHEMICALS & PLASTICS TECHNOLOGY CORP
Application year: 1995
Main classification: C07B57
IPC codes: C07C45, C07C51