Optically active monophosphino carboxylic acid derivative

Abstract: An optically active monophosphino carboxylic acid derivative of formula (I): wherein: each R 1 independently represents a C 1-6 alkyl group or phenyl group which is unsubstituted or substituted with a C 1-4 alkyl group or C 1-4 alkoxy group; R 2 represents a C 1-4 alkyl group; and R 3 and R 4 each independently represents a hydrogen atom, or a C 1-4 alkyl group or phenyl group which is unsubstituted or substituted with a C 1-4 alkyl or C 1-4 alkoxy group.

Description: The present invention concerns an asymmetric reaction catalyst and a ligand therefor which is useful for the production of medical or agricultural chemicals or intermediates thereof. It is important that biologically active agents are optically active since the biobodies on which they act have asymmetric structures. It has been strongly demanded socially to produce and provide only the optically active biologically active agents such as medical or agricultural chemicals to reduce side-effects and protect the environment. Development of a process for synthesizing optically active compounds is an important subject of study for satisfying such a demand, and has been studied energetically world-wide both in official and civil organizations. Development of a process for producing optically active compounds using asymmetric reaction catalysts is extremely useful for the chemical synthesis industry since this enables the production of optically active compounds in a great amount from a small amount of an asymmetric source. A number of asymmetric reaction catalysts have been developed ("Homogeneous Catalysis with Metal Phosphine Complex", ed. by L. H. Pignolet, Plenum Press, New York, 1983). Among them, several practical asymmetric oxidizing catalysts and asymmetric reduction catalysts have been reported ("Asymmetric Synthesis", Vol. 5, ed. by J. D. Morrison, Academic Press, Orlando (1985)). However, from the industrial viewpoint there are still many problems to be solved such as economic advantages and catalyst reaction conditions. While several studies at the laboratory level have been seen, for example, an asymmetric allylating reaction catalyst (B. M. Trost, Tetrahedron, 33, 2615 (1977); R. F Heck, "Palladium Reagents in Organic Synthesis", Academic Press, London, 117 (1985); J. Tsuji, Tetrahedron, 42, 4361 (1986) (hereinafter referred to as literature a ); and JP-A-5-306291 (hereinafter referred to as literature b )), development of a catalyst which can be utilized industrially has been demanded. Phosphorus, Sulfur, and Silicon, 1989, Vol. 42, pp 211-222 discloses synthesis of some functionalized phosphinocarboxylic acids. Tetrahedron Letters, Vol. 31, No. 27, pp 3905-3908, 1990 discloses synthesis of chiral phosphinocarboxylic ligands, trans-2-(diphenylphosphino) cycloalkanecarboxylic acids. We have earnestly sought an economic and highly selective asymmetric allylation catalyst which can be utilized industrially and, as a result, has found that a particular monophosphino carboxylic acid derivative can be an asymmetric ligand capable of satisfying this purpose. The present invention accordingly provides an optically active monophosphino carboxylic acid derivative of formula (I): wherein: each R 1 independently represents a C 1-6 alkyl group or phenyl group which is unsubstituted or substituted with a C 1-4 alkyl group or C 1-4 alkoxy group; R 2 represents a C 1-4 alkyl group; and R 3 and R 4 each independently represents a hydrogen atom, or a C 1-4 alkyl group or a phenyl group which is unsubstituted or substituted with a C 1-4 alkyl or C 1-4 alkoxy group. The present invention also provides a complex of a derivative of formula (I) and a transition metal compound. The present invention further provides a process for the preparation of a derivative of formula (I) as set out below. The present invention additionally provides the use of a complex as defined above as a catalyst in an asymmetric reaction. Since the asymmetric ligand of formula (I) can be easily produced from inexpensive starting materials as shown in the later Examples, it is a highly economical asymmetric ligand. A transition metal complex thereof can be a reaction catalyst to produce an optically active compound. Particularly, the palladium complex is a catalyst suitable for an asymmetric allylating reaction. A prominent feature of the transition metal catalyst comprising the ligand of formula (I) is that the field of application is large since it can be utilized as an effective homogeneous catalyst both in water or a mixed solvent of water and an organic solvent due to its water solubility. The fields of application of conventional asymmetric reaction catalysts having organic ligands have been restricted due to their water insolubility. Further, the ligand of formula (I) can form complexes with various transition metal compounds and can be various asymmetric reaction catalysts depending on the central metals of the complexes. For example, the present inventor has already disclosed that a rhodium complex of this type can be an extremely useful asymmetric reduction catalyst (Minami et al., Chem. Lett., 1986, 613). Further, in common with the (ortho-diphenylphosphino) benzoic acid - nickel complex (R. F. MASON, USP No. 3686351) found by Shell Co., it can be expected that the nickel complex of the present ligand is an asymmetric polymerization catalyst for propylene. The derivative of the present invention is now explained in further detail. R 1 represents a C 1-6 alkyl group or phenyl group which is unsubstituted or substituted with a C 1-4 alkyl group or C 1-4 alkoxy group. The C 1-6 alkyl group may be linear, branched or cyclic and there can be mentioned, for example, methyl, ethyl, n-propyl, i-propyl, c-propyl, n-butyl, s-butyl, t-butyl c-butyl, n-pentyl, i-pentyl, 2-methylbutyl, neopentyl, 1-ethylpropyl, c-pentyl, n-hexyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,3-dimethylbutyl, 2-ethylbutyl and c-hexyl. The phenyl group is unsubstituted or substituted with a C 1-4 alkyl group or C 1-4 alkoxy group. The number of substituents can be from 1 to 5, and the alkyl group and the alkoxy group may be present either alone or together. The C 1-4 alkyl group may be linear, branched or cyclic and there can be mentioned, for example, methyl, ethyl, n-propyl, i-propyl, c-propyl, n-butyl, s-butyl, t-butyl and c-butyl. The C 1-4 alkoxy group may be linear, branched or cyclic and there can be mentioned, for example, methoxy, ethoxy, n-propoxy, i-propoxy, c-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy and c-butoxy. R 1 is preferably a phenyl group which is unsubstituted or substituted with a C 1-4 alkyl group or C 1-4 alkoxy group. R 2 represents a C 1-4 alkyl group. As the C 1-4 alkyl group, there can be mentioned those described above. R 3 and R 4 each independently represents a hydrogen atom, or a C 1-4 alkyl group or phenyl group which is unsubstituted or substituted with a C 1-4 alkyl group or C 1-4 alkoxy group. As the C 1-4 alkyl group or the phenyl group which may be unsubstituted or substituted with a C 1-4 alkyl group or C 1-4 alkoxy group, there can be mentioned those described above. Preferred compounds of the present invention are those in which R 1 represents a phenyl group which is unsubstituted or substituted with a C 1-4 alkyl group or C 1-4 alkoxy group, and R 3 and R 4 each independently represents a hydrogen atom or a C 1-4 alkyl group. The process reacting a substituted acrylic provided by the invention, and referred to above, comprises acid derivative of formula (II) with a phosphine compound of formula (III) in the presence of a base to form a (±)-monophosphino carboxylic acid derivative of formula (IV), which is then subjected to optical resolution and, if necessary, to separation of diastereomers, to produce the derivative of formula (I) in accordance with the following reaction scheme: A substituted acrylic acid derivative of formula (II) is reacted with a phosphine compound of formula (III) in the presence of a base to obtain a (±)-monophosphino carboxylic acid derivative of formula (IV), which is then subjected to optical resolution and if necessary, to separation of diastereomers, to produce the optically active derivative of formula (I). The mark "*" in formula (I) indicates that the absolute configuration on the indicated asymmetric carbon is either R or S, while the mark "(*)" indicates that the absolute configuration on the indicated asymmetric carbon to which the substituents except for the hydrogen atom are bonded is R or S, or a mixture thereof. The molar ratio between the starting materials in the reaction can be set freely but it is usually sufficient to use 1 to 5 moles, preferably 1.2 to 2 moles, of the phosphine compound of formula (III) per mole of the substituted acrylic acid derivative of formula (II). As the base, various metal bases can be used, for example, n-butyl lithium, t-butyl lithium, phenyl lithium, lithium diisopropylamide, lithium hydride, sodium hydride, calcium hydride and sodium amide. There is no particular restriction on the reaction solvent so long as it does not interfere with the reaction. There can be used, for example, ethers such as tetrahydrofuran, 1,4-dioxane, diethyl ether and 1,2-dimethoxyethane, benzene type solvents such as benzene, toluene and xylene, alkanes such as hexane and pentane, amide type solvents such as N,N-dimethylformamide and N-methylpyrrolidone, hexamethyl phosphoric triamide (HMPA), dimethyl sulfoxide (DMSO) or a mixed solvent thereof. The reaction is usually conducted at from -100°C to room temperature, and often conducted, preferably, at from -80°C to -10°C. To obtain the optically active derivative of formula (I) from the (±)-monophosphino carboxylic acid derivative of formula (IV), optical resolution methods usually employed can be used. For example, it can be produced by a chromatographic separation method using an optically active column, a preferential crystallization method, or an asymmetric hydrolysis method of the carboxylic acid ester of formula (IV) using an enzyme such as lipase (reaction kinetic resolution method; an optically active phosphino carboxylic acid ester and an optically active phosphino carboxylic acid as an epimer thereof can be obtained). In a case of a (±)-carboxylic acid (IV) in which R 3 is a hydrogen atom, a diastereomer salt resolution method using an optically active amine can be used and satisfactory results are often obtained by this method. Accordingly, also in a case of an optically active monophosphino carboxylic acid ester (I) (R 3 ≠ H), subjecting a corresponding (±)-monophosphino carboxylic acid ester of formula (IV) once to hydrolyzing reaction to provide a (±)-monophosphino carboxylic acid, and then subjecting it to diastereomer salt resolution using an optically active amine to obtain an optically active monophosphino carboxylic acid, which is subjected to an esterifying reaction employed conventionally, may be adopted. As the optically active amine used, there can be mentioned naturally occurring alkaloids such as quinine, quinidine, cinchonine, brucine and ephedrine, basic amino acids such as lysine and arginine or optically active synthetic amines such as α-methylbenzylamine, α-ethylbenzylamine, 1-(p-tolyl)ethylamine and 1-phenyl-2-(p-tolyl)ethylamine. Another production process comprising condensing a racemic carboxylic acid of formula (IV) with an optically active alcohol or optically active amine to obtain an ester or amide as a diastereomeric mixture, which is subjected to diastereomer separation using recrystallization or various kinds of chromatography, and then successively to hydrolysis to obtain an optically active monophosphino carboxylic acid of formula (I) can be also adopted. For the optically active alcohol or amine used and the reaction conditions and operation procedures after using them, those used in the usual optical resolution methods may be adopted with no trouble. The derivative of formula (I) thus obtained is extremely useful as a ligand of an asymmetric reaction catalyst. The ligand can form complexes with various transition metal compounds. As examples of the transition metal compounds, there can be mentioned hydrochlorides, sulfates, nitrates, acetates, phosphine or carbonyl complexes of titanium, vanadium, chromium, manganese, molybdenum, tin, copper, zinc, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium or platinum. As specific examples, there can be mentioned palladium hydrochloride, palladium sulfate, palladium nitrate and palladium acetate. They can be asymmetric reaction catalysts, for example, for an asymmetric alkylating reaction, asymmetric allylating reaction, asymmetric reducing reaction, asymmetric oxidizing reaction or asymmetric addition reaction by changing the transition metal compounds or reaction conditions. It is not particularly necessary to isolate them but a complex may be formed in a reaction system by adding a ligand and a transition metal compound to the system. In this case, the amount of the transition metal compound added is from 0.01 to 10 molar equivalents, preferably from 0.1 to 2 molar equivalents, on the basis of the ligand. The amount of the catalyst used is from 0.01 mol% to 20 mol%, preferably 0.1 mol% to 5 mol%. There are no particular restrictions for the reaction temperature and the reaction solvent and they may depend on the kind of reaction to be conducted. Further, other ligands such as an imidazole derivative, pyridine derivative or phosphine derivative may be optionally present together. A complex of a palladium salt selected from the transition metal compounds described above with the compound of formula (I) is an asymmetric reaction catalyst which is particularly effective for the asymmetric allylating reaction. The allylating reaction mentioned herein can include a wide variety type of allylating reactions as disclosed, for example, in literature (a) described previously. The reaction can be represented, for example, by the following reaction scheme; In the reaction formula, R 5 , R 6 , R 7 and R 8 each independently represents a hydrogen atom, alkyl group or aryl group, or R 5 and R 6 , R 6 and R 7 or R 5 and R 8 may join to form a C 4-7 cycloalkyl or cycloalkenyl ring, wherein the alkyl group may be substituted at any position with an alkoxy group or acyl group; X represents an acyloxy group, alkoxycarbonyloxy group, dialkylaminocarbonyloxy group, dialkylamino group, nitro group, sulfonic group, dialkylphosphonyloxy group or chloro atom; Nu represents a carbon nucleophilic agent usually used in organic synthesis chemistry such as a β-ketoester derivative, malonic acid derivative, cyano acetic acid derivative, β-ketophosphonic acid derivative, phosphonyl acetic acid derivative, cyanomethyl phosphonic acid derivative, alkyl or aryl thiomethyl phosphonic acid derivative and various kinds of ester derivatives thereof, or represents a nitrogen nucleophilic agent such as a primary or secondary amine, amide, phosphoric acid amide derivative or sulfone amide derivative. The asymmetric allylating reaction represented by the reaction scheme described above can result in excellent asymmetric induction using the asymmetric catalyst formed from the ligand of formula (I) and the palladium salt instead of a 0-valent palladium complex used in the allylating reaction described, for example, in the literature (a). It has been shown that the asymmetry inducing capacity of the present asymmetric catalyst is larger in comparison with the capacity of the catalyst described in the literature (b). While the present reaction can be conducted under a neutral condition, the reaction may proceed or be completed rapidly when it is conducted with addition of various kinds of organic bases or inorganic metal bases such as trialkylamines, alkyl metal hydrides, metal hydrogen carbonate and metal carbonates. For other reaction conditions, those as described in the previous section relating to asymmetric reactions, as well as those similar to the reaction condition disclosed, for example, in the literature (a) may be adopted with no trouble. The optically active allylated derivatives obtained are useful as biologically active compounds such as medicines and agricultural chemicals and as intermediates for the production thereof. The present invention is now further described in the following Examples (Reference Examples, Synthetic Examples and Asymmetric Catalytic Reaction Examples). The terms "IR", "NMR" and "MS" mean "infrared absorption spectrum", "nuclear magnetic resonance spectrum" and "mass analysis spectrum", respectively. Reference Example 1 (±)-t-butyl-3-diphenylphosphino butanoate Under an argon atmosphere, a solution of n-butyl lithium in hexane (7.32 ml, 12 mmol) was added to a solution of diphenylphosphine (2.23 g, 12 mmol) in tetrahydrofuran (14 ml) at -78°C and stirred at that temperature for 30 min. Hexamethylphosphoric triamide (2.09 ml, 12 mmol) was added thereto and the temperature was once elevated to 0°C to dissolve the solidified hexamethyl phosphoric triamide and then rapidly lowered to -78°C. Successively, t-butyl chrotonate (1.42 g, 10 mmol) was added and stirred at that temperature for 10 min, and then an aqueous saturated solution of ammonium chloride was added followed by extraction with ether. After washing the organic layer with water and drying over anhydrous sodium sulfate, the solvent was distilled off under reduced pressure and the residue was purified by silica gel column chromatography (ether/hexane = 1/3) to obtain the above captioned compound. 1 H-NMR(CDCl 3 ) δ 1.11(dd, J d(H-H) = 7.0 Hz, J d(P-H) = 15.0 Hz, 3H, CH 3 ), 1.48(s, 9H, t-Bu), 1.70-2.80(m, 3H, CH 2 and CH), 7.33-7.52(m, 10H, Ar-H). Reference Example 2 (±)-3-diphenylphospino butanoic acid Under an argon atmosphere, p-toluene sulfonic acid (7.61 g, 40 mmol) was added to a solution of (±)-t-butyl-3-diphenylphosphino butanoate (2.60 g, 7.9 mmol) in benzene (20 ml) and the mixture was refluxed under heating for three hours. The reaction solution was concentrated under reduced pressure and the residue was dissolved with chloroform, washed with water and dried over anhydrous sodium sulfate. Successively, the solvent was distilled off under a reduced pressure and the residue was purified by silica gel column chromatography to obtain the above captioned compound. Amount obtained: 2.07 g Yield : 76% IR(neat) 1710 cm -1 1 H-NMR(CDCl 3 ) δ 1.11(dd, J d(H-H) = 7.0 Hz, J d(P-H) = 15.0 Hz, 3H, CH 3 ), 2.19(ddd, J d(H-H) = 16.0, 11.1Hz, J d(P-H) = 5.2Hz, 1H, CH 2 ), 2.50(ddd, J d(H-H) = 15.8, 3.4Hz, J d(P-H) = 8.2Hz, 1H, CH 2 ), 2.86(dddq, J q(P-H) = 7.0Hz, J d(H-H) = 11.1, 3.4Hz, J d(P-H) = 17.9Hz, 1H, CH 2 ), 7.33-7.52(m, 10H, Ar-H). 31 P-NMR(CDCl 3 ) δ-0.67(s) (from H 3 PO 4 ) EIMS m/z 272 (M + ) Example 1 (+)-3-diphenylphosphino butanoic acid Under an argon atmosphere, (±)-3-diphenylphosphino butanoic acid (2.0 g, 7.4 mmol) was dissolved in acetone (5 ml), to which (+)-phenethylamine (0.55 ml, 4.4 mmol) was added and stirred under heating for 30 min. The temperature was lowered to -78°C, and elevated up to 0°C simultaneously with deposition of crystals and kept for three hours to completely crystallize the ammonium salt. After being filtered under a nitrogen atmosphere and washed with a mixed solvent of ethyl acetate/hexane (1/9), the crystals were dried and the optical rotation thereof was measured. Further, the ammonium salt was recrystallizzed repeatedly from ethyl acetate/hexane until no change of the optical rotation values was observed. The salt was dissolved in chloroform and washed with 2N-hydrochloric acid to form the carboxylic acid. After distilling off the solvent under reduced pressure, the residue was purified by silica gel chromatography to obtain the above captioned compound. Amount obtained: 620 mg Optical rotation: [α] D = +22.0°. Example 2 (-)-3-diphenylphosphino butanoic acid The above-captioned compound was obtained by the same procedures as in Example 1 except that (-)-phenethylamine was used instead of (+)-phenethylamine in Example 1. Optical rotation [α] D = -21.9° Asymmetric Catalytic Reaction Example 1 (Asymmetric Allylating Reaction) Under an argon atmosphere, a solution of (-)-3-diphenylphosphino butanoic acid (17 mg, 0.06 mmol) in tetrahydrofuran (4 ml) prepared in Example 2 was added to palladium acetate (7 mg, 0.03 mmol). After confirming the formation of a palladium complex by means of the turbidity of the solution, cyclohexenyl acetate (0.21 g, 1.5 mmol) was added. Ethyl diethylphosphono acetate carbo anions prepared from sodium hydride (0.08 g, 2.0 mmol) and ethyl diethylphosphono acetate (0.50 g, 2.2 mmol) were added thereto. After stirring at 60°C for 4 hours, 2N-hydrochloric acid was added to the reaction mixture, which was extracted with ethyl acetate and dried over anhydrous sodium sulfate. After distilling off the solvent under reduced pressure, optically active ethyl 2-cyclohexenyl diethyl phosphono acetate was obtained by purification with silica gel thin layer chromatography. Amount obtained: 0.46 g Yield: 100 % Optical Yield: 77% ee IR(neat) 1730, 1650, 1250 cm -1 1 H-NMR(CDCl 3 ) δ 1.29(t, J=7.0Hz, 3H, CH 3 ), 1.34(t, J=7.0Hz, 6H, CH 3 ), 1.4-2.2(m, 6H, CH 2 ), 2.4-3.2(m, 2H, CH), 4.11(q, J=7.0Hz, 2H, CO 2 CH 2 ), 4.22(q, J=7.0Hz, 4H, POCH 2 ), 5.2-6.2(m, 2H, CH=CH). The optical yield in the asymmetric allylating reaction was determined after conversion of the product into a diastereomeric amide, as shown below. Determination of Optical Yield Under an argon atmosphere, sodium hydride (62.9 mg, 1.6 mmol) was added to a tetrahydrofuran solution (4 ml) of ethyl 2-cyclohexenyldiethyl phosphono acetate (0.40 g, 1.31 mmol) obtained by the asymmetric allylating reaction described above. After stirring at room temperature for 30 min, paraformaldehyde (0.12 g, 4.0 mmol) was added and stirred at room temperature for further 3 hours. After the reaction was completed, the 2N-hydrochloric acid was added and after extracting the reaction solution with ethyl acetate, the organic phase was dried over anhydrous sodium sulfate. After distilling off the solvent under reduced pressure an optically active ethyl 2-(2-cyclohexenyl) acrylate was obtained by purification with silica gel thin layer chromatography (benzene/hexane = 1/1). Amount obtained: 0.22 g Yield : 91.7% Optical rotation: [α] D = 59.0 (c=1.66, CH 2 Cl 2 ) Further, an aqueous solution (4 ml) of sodium hydroxide (0.11 g, 2.75 mmol) was added to a solution of ethyl 2-(2-cyclohexenyl) acrylate (0.10 g, 0.55 mmol) in ethanol (8 ml) and the mixture was refluxed under heating for 2 hours. After the hydrolysis was completed, 2N-hydrochloric acid was added to the reaction mixture, which was extracted with chloroform and then dried over anhydrous sodium sulfate. After distilling off the solvent under reduced pressure, to the residue a solution of 2-chloro-1-methyl pyridinium pyridinium iodide (0.21 g, 0.83 mmol) in dichloromethane (3 ml) was added. A solution of triethylamine (0.23 ml, 1.65 mmol) and (+)-phenethylamine (0.10 ml, 0.83 mmol) in dichloromethane (2 ml) was added thereto and stirred at a room temperature for 3 hours. After the reaction was completed, 2N-hydrochloric acid was added to the reaction mixture, which was extracted with chloroform and then dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure and the resultant compound was analyzed by high performance liquid chromatography, to determine the optical yield in the asymmetric allylating reaction.

Claims: An optically active monophosphino carboxylic acid derivative of formula (I): wherein: each R 1 independently represents a C 1-6 alkyl group or phenyl group which is unsubstituted or substituted with a C 1-4 alkyl group or C 1-4 alkoxy group; R 2 represents a C 1-4 alkyl group; and R 3 and R 4 each independently represents a hydrogen atom, or a C 1-4 alkyl group or phenyl group which is unsubstituted or substituted with a C 1-4 alkyl or C 1-4 alkoxy group. A derivative according to claim 1 wherein: R 1 represents a phenyl group which is unsubstituted or substituted with a C 1-4 alkyl group or C 1-4 alkoxy group; and R 3 and R 4 each independently represents a hydrogen atom or a C 1-4 alkyl group. A complex of a derivative as defined in claim 1 or 2 and a transition metal compound. A complex according to claim 3 wherein the transition metal compound is a palladium compound or salt. A process for the preparation of a derivative as defined in claim 1 or 2 which comprises reacting a substituted acrylic acid derivative of formula (II) with a phosphine compound of formula (III) in the presence of a base to form a (±)-monophosphino carboxylic acid derivative of formula (IV), which is then subjected to optical resolution and, if necessary, to separation of diastereomers, to produce the derivative of formula (I) in accordance with the following reaction scheme: wherein R 1 , R 2 , R 3 and R 4 are as defined in claim 1. Use of a complex as defined in claim 3 or 4 as a catalyst in an asymmetric reaction. Use according to claim 6 wherein the reaction is an asymmetric allylating reaction.

Inventors: MINAMI TOHRU, MINAMI, TOHRU
Applicants: NISSAN CHEMICAL IND LTD, NISSAN CHEMICAL INDUSTRIES LTD.
Application year: 1996
Main classification: C07F9
IPC codes: C07F15, C07B53, C07F9