PROCESS FOR THE PREPARATION OF BETA-GAMMA UNSATURATED ESTERS

Abstract: A process for the carbonylation of allylic butenyl ether (e.g., methyl crotyl ether, 3-methoxybutene-1 and mixtures thereof) or mixture of butadiene and alcohol (e.g., methanol) and production of beta-gamma unsaturated carboxylic acid esters (e.g., methyl-3-pentenoate) utilizing a rhodium-containing catalyst (e.g., dicarbonylacetylacetonate rhodium(I) or the like) promoted with an iodide-containing compound (e.g., HI, AlI3, SnI4, TiI4, CrI3, and CoI2 or the like). Such a process is particularly useful in the production of difunctional monomers and intermediates in the synthesis of adipic acid. The representative reaction showing (a) butadiene in the presence of methanol under catalytic reaction conditions producing the 3-methoxybutene-1 intermediate (a positional isomer of methyl crotyl ether) which is then combined with carbon monoxide to produce methyl pentenoate is illustrative of the overall carbonylation.

Description: TITLE OF THE INVENTION PROCESS FOR THE PREPARATION OF BETA-GAMMA UNSATURATED ESTERS BACKGROUND OF THE INVENTION 1. Field of the Invention: The present invention relates to a process for the preparation of beta-gamma unsaturated carboxylic acid esters by catalytic carbonylation starting with either an allylic butentyl ether or mixture of butadiene and an alcohol. More specifically but not by way of limitation, the invention relates to the use of a rhodium-containing catalyst in combination with an iodide promoter for the carbonylation of methyl crotyl ether, 3-methoxybutene-l and mixtures thereof to produce methyl-3-pentenoate. 1. Description of Related Art The use of rhodium-containing catalyst with various types of co-catalysts and promoters for the carbonylation of a variety of saturated and unsaturated organic compounds is generally known. For example, U.S. Pat. No. 4,603,020 claims a process for the carbonylation of O-acetyl compounds, such as acetic anhydride, at 130 to 250 °C using a rhodium catalyst and an aluminum accelerator. U.S. Pat. No. 4,625,058 teaches a similar process but uses boron, bismuth or tertiary amide compounds as accelerators. U.S. Pat. No. 4,642,370 discloses a process for the carbonylation of hydrocarbyl halides which uses a boron, silicon, aluminum, or zirconium accelerator. U.S. Pat. No. 4,563,309 claims a process for the production of carboxylic acid anhydride of the formula RC(0)0(0)CCH 3 by reaction of a methyl carboxylate ester of formula RC(0)OCH 3 with carbon monoxide in the presence of a rhodium catalyst and a phosphorous-containing ligand. European patent application 0 428 979 A2 discloses the carbonylation of allylic butenols and butenol esters using a rhodium catalysts and a hydrogen bromide or hydrogen iodide promoter under anhydrous conditions for the production of 3-pentenoic acid. BRIEF SUMMARY OF THE INVENTION In view of the above prior art, it has now been discovered that the an allylic butenyl ether such as an alkyl crotyl ether or a corresponding mixture of butadiene and an alkanol will readily undergo carbonylation directly to a beta-gamma unsaturated carboxylic acid ester, such as alkyl-3-pentenoate, at high selectivity and high activity by use of a rhodium-containing catalyst in the presence of an iodide-containing promoter. Thus the present invention provides a process for the carbonylation of allylic butenyl ether or mixture of butadiene and an alcohol and the production of beta-gamma unsaturated carboxylic acid ester comprising the steps of: (a) reacting an allylic butenyl ether or mixture of butadiene and an alcohol with carbon monoxide in the presence of a rhodium-containing catalyst and an iodide-containing promoter; and (b) recovering a beta-gamma unsaturated carboxylic acid ester. In one embodiment of the invention the allylic butenyl ether is selected from the group consisting of methyl crotyl ether, 3-methoxybutene-l and mixtures thereof and the beta-gamma unsaturated carboxylic acid ester is methyl-3-pentenoate. In another embodiment, the carbonylation involves reacting butadiene and methanol and the beta-gamma unsaturated carboxylic acid ester is again methyl-3-pentenoate. Preferably, the iodide-containing promoter is selected from the group consisting of HI, A1I 3 , Snl 4 , Til 4 , Crl 3 , and CoI 2 and the rhodium-containing catalyst is dicarbonylacetylacetonate rhodium(I). DETAILED DESCRIPTION OF INVENTION The process of the present invention involves a rhodium catalyzed carbonylation of an allylic butenyl ether to produce a beta-gamma unsaturated carboxylic acid ester wherein the rhodium-contaming catalyst is promoted by the use of HI, HBr or a metal halide salt. The allylic butenyl ether being carbonylated is either an alkyl crotyl ether, a positional isomer thereof such as 3-alkoxybutene-l or mixtures of the same. For purposes of the present invention, mixtures that produce the allylic butenyl ether or equivalent in-situ are equivalent staring materials and such butadiene in the presence of an alkanol is to be considered an alternate starting material. The following representative reaction showing a butadiene in the presence of methanol under catalytic reaction conditions producing the 3-methoxybutene-l intermediate (a positional isomer of methyl crotyl ether) which is then combines with carbon monoxide to produce methyl pentenoate is illustrative of the overall carbonylation. Suitable allylic butenyl ethers are of the form H \ / C=C H R 1 C-OR 4 R 3 where one of the groups R , R , and R is methyl and the other two groups are H and wherein R 4 is a C \ to Cio alkyl. It should be appreciated that acceptable allylic compounds includes both cis and trans isomers, other positional isomers such as that illustrated by 3-alkoybutene-l and crotyl ester as well as mixtures of various allylic compounds. Also, for purposes of the present invention, butadiene in combination with a to do alkyl alcohol leads to in-situ ether formation and thus total equivalency relative to the use of allylic butenyl ether as starting material for the carbonylation reaction. The reaction can be performed at a temperature in the range of 40 °C to about 200 °C. Below 40 °C the reaction becomes too slow to be commercially feasible, and above 200 °C the formation of undesirable products leads to significant yield losses. Preferably the reaction temperature is between 90 °C and 150 °C and most preferably between 90 °C and 150 °C. Suitable total pressures for the reaction are in the range 25 to 3,000 psig. Preferably the pressure is between 100 and 2,000 psig with 200 to 1,000 psig being most preferred. The source of the carbon monoxide (CO) reactant for the present invention is not crucial. Commercially available grades of carbon monoxide are acceptable. As such, the carbon monoxide can contain inert impurities such as carbon dioxide, methane, nitrogen, noble gasses, and other hydrocarbon having up to four carbon atoms. Preferably the carbon monoxide also contains hydrogen typically at about a ten mole percent concentration relative to the carbon monoxide. At least 1 molar equivalent of carbon monoxide to allylic butenyl ether or butadiene is needed. Typically, an excess of CO is used. Suitable solvents for this process are those which are compatible with the reactants and the catalyst system under the reaction conditions. Such solvents include aromatic hydrocarbon solvents, saturated halocarbon solvents, and mixtures thereof. Carboxylic acid esters and lactones, such as methyl-3- pentenoate, valerolactone and the like, are also acceptable solvents. Suitable aromatic hydrocarbon solvents include benzene, toluene, 1,2,4-trichlorobenzene and other C 2 to C alkyl substituted benzenes. Suitable saturated halocarbon solvents include chlorinated and fluormated hydrocarbons such as methylene chloride, dichloroethane and chloroform as well as the so-called HCFC's including in particular HCFC-113 (FCC1 2 CF 2 C1) and HCFC-123 (CHC1 2 CF 3 ) or the like. The most preferred solvents are toluene, HCFC-113 and HCFC- 123. Alternatively, the process of this invention where the starting material is a methoxybutene may be run in the absence of solvent. The rhodium catalyst can be provided from any source or by any material which will produce rhodium ions under the carbonylation reaction conditions. Among the materials which can be employed as the source of the rhodium catalyst are rhodium metal, rhodium salts, rhodium oxides, rhodium carbonyl compounds, organorhodium compounds, coordination compounds of rhodium, and mixtures thereof. Specific examples of such compounds include, but are not limited to, RhCl 3 , RI 3 , Rh(CO) 2 I 3 , Rh(CO)I 3 , Rh 4 (CO) 12 , Rh 6 (CO) 16 , Rh(acac) 3 , Rh(CO) 2 (acac), Rh(C 2 H 4 ) 2 (acac), [Rh(C 2 H 4 ) Cl] 2 , [Rh(CO) 2 Cl] 2 , [Rh(CO) 2 Br] 2 , Rh(COD)(acac), [Rh(COD)Cl] 2 , RhCl(CO)(PPh 3 ) 2 , Rh 2 [0 2 C(CR 2 ) 6 CH 3 ] 4 , and Rh 2 (acetate) 4 , where acac is acetylacetonate, COD is 1 ,5-cyclooctadiene, and Ph is phenyl. Rhodium compounds containing bidentate phosphorous or nitrogen ligands should be avoided. Preferred sources of rhodium catalyst include rhodium(I) compounds such as Rh(CO) 2 (acac), [Rh(CO) 2 Cl] 2 , [Rh(COD)Cl] 2 , Rh(COD)(acac), and rhodium iodide compounds such as Rhl 3 and Rh(CO) 2 I 3 . Most preferably the rhodium- containing compound is Rh(CO) 2 (acac). Suitable concentrations of rhodium in the reaction are in the range of 0.005 to 0.50 % by weight of rhodium metal based on the reaction medium. Preferably the concentration of rhodium is in the range of 0.02 to 0.20 wt%. Although high reaction rates on a per Rh basis can be obtained even at low concentrations of Rh, it is generally more economical to operate at Rh concentrations above 0.01 wt%. Similarly, Rh concentrations below 2.0 wt% are preferred to minimize the formation of unwanted by-products. The rhodium, which may be pre-formed or generated in situ, must be promoted by HI, HBr or a metal halide, preferably by HI or a metal iodide, to achieve a satisfactory rate and selectivity to pentenoate ester. Examples of suitable promoters are the acid halides as well as halides of Groups IIB, III A, IIIB, IVA, IVB, VIB, VII, VIII of the periodic table. Preferred promoters are those where the halide is iodide, such as but not limited to HI, A1I 3 , Snl , Til 4 , Crl 3 , and CoI 2 . The molar ratio of promoter to rhodium can be in the range of about 1:1 to about 50:1. Although high selectivities to the desired methyl-3- penetoate can be obtained even at low promoter to rhodium ratios, the rate of formation of methyl-3-pentenoate on a per Rh basis decreases significantly when the molar ratio of promoter to rhodium is less than 1. This decrease in reaction rates, coupled with the high cost of rhodium makes it more economical to use promoter to rhodium ratios greater than 1 : 1. Similarly, the molar ratio of promoter to rhodium must be less than about 50 to obtain reasonable yields of the unsaturated ester. Preferably, the molar ratio of promoter to rhodium is between about 10 and about 30. Reaction times can be varied and depend on choice of reactants, solvent, catalyst and promoter as well as their respective concentration and reaction conditions such as temperature and pressure. Residence times of the order of about 1 minute to about 20 hours are acceptable. The reaction of the present invention may be carried out in a batch or continuous mode. The products can be isolated and recovered by any of the techniques generally known in the art including by example but not limited thereto, extraction, distillation or the like. The following examples are present to further illustrate specific features and advantages of the present invention and as such are not intended to limit the scope of the invention. The conversion data reported is based on quantitative measurement of the relative amount of the primary or limiting reactant (e.g., 3-methoxybutene-l or alternatively butadiene) that is not consumed by chemical reaction. The selectivity to the desired methyl- 3-pentenoate (M3P) is based on and reported as the amount of methyl ester produced relative to the amount of the primary reactant consumed by the reaction. Example 1 3-Methoxybutene-l Carbonylation to M3P with Rh Catalyst Promoted by Aluminum Iodide: A 120 mL mechanically stirred Hastelloy-C autoclave was charged with 0.258 grams (0.1 mmole) of dicarbonylacetylacetonate rhodium(I), 1.63 grams (4.0 mmole) of anhydrous aluminum iodide and 72.1 grams (83.4 mL) toluene. The reaction vessel was pressurized to 400 psig with a 90/10 mixture of CO and hydrogen. The solution was heated to a temperature of 120 °C and the carbonylation reaction was initiated by injecting a solution of 8.6 grams (100 mmole) of 3-methoxybutene-l and 1.0 grams of ortho- dichlorobenzene (ODCB, internal GC standard) in 5 grams of toluene. The total pressure was then adjusted to 700 psig with the 90/10 CO/H 2 . Carbon monoxide and H (90/10 ratio) were continuously fed to the autoclave from a reservoir so as to maintain the total pressure constant at 700 psig. Samples were removed at intervals for GC analysis on a DBFFAP 30 M J&W Scientific capillary GC column. The analysis showed that 62.5% of the methoxybutene charged was converted in the first hour and the selectivity to methyl-3- pentenoate (M3P; cis and trans isomers) was 93.9%. After 4 hours the conversion was 98% and the selectivity to M3P was 93%. The only significant by-products were mixed butenes and butadiene (not separated, 5.2%), valerolactone (1.5%) and 3-pentenoic acid (0.3%). The first order rate constant for the formation of M3P was 1.02 hr 1 , corresponding to a space-time yield (STY) of 734 mmole M3P per liter per hour. Example 2 Methoxybutene Carbonylation to M3P With Rh Catalyst Promoted by Aluminum Iodide (Higher Iodide/Rh ratio and Higher Temperature): The experiment in Example 1 was repeated except that the 3-methoxybutene-l was replaced with a 70/30 mixture of l-methoxybutene-2 (methyl crotyl ether) and 3-methoxybutene-l, the iodide to rhodium ratio was increased from 12/1 to 18/1 and the temperature was increased to 130°C. The GC analysis showed a methoxybutene conversion of 85.8% after 30 minutes and a selectivity to M3P of 82%. After 60 minutes the conversion was 97% and the selectivity to M3P was 84.6%. The first order rate constant for the formation of M3P was 2.96 hr "1 , corresponding to a space-time yield (STY) of 2,135 mmole M3P per liter per hour. Example 3 Carbonylation of 3 -Methoxybutene- 1 using a Rhodium Catalyst and aqueous HI Promoter: A 25 mL glass lined pressure vessel was charges with 5 mL of a solution containing 5.9 grams (69 mmol) of 3-methoxybutene-l (3MB1), 0.258 grams (1.0 mmol) of dicarbonylacetylacetonate rhodium(I), 1.34 grams (6.0 mmol) of 57% aqueous HI solution, and 1.00 grams of o-dichlorobenzene (internal gas chromatograph standard) in 100 mL of toluene. The pressure vessel was freed from air by purging first with nitrogen (twice) and then with carbon monoxide containing 10 mol% hydrogen (twice). The vessel was then pressurized to 500 psig of 90/10 CO/H 2 and heated to 120 °C with agitation for 3 hours. The heat was shut off, the pressure vessel was allowed to cool to room temperature and the excess gases were vented. The product was analyzed by gas chromatography on a DBFFAP 30 M J&W Scientific capillary GC column. The results of the analysis are summarized below: Before esterification mmol/100 mL - Butadiene 13.3 Methoxybutenes 0.9 3-Pentnoic acid 9.0 Methyl-3-pentenoate 54.9 Methoxybutene conversion was 94.0%, selectivity to methyl-3-pentonate (M3P) was 84.8% and selectivity to 3-pentenoic acid was 13.9%. Product accounting was 99%. Example 4 In a manner analogous to the procedure employed in Example 3, an additional run was performed except that 0.064 grams of methanol (MeOH) per 100 grams of methoxybutene (2 equivalents per 100 equivalents) was added. The resulting data for this example as well as the corresponding data from Example 1 are presented in Table 1. Example 5 The procedure employed in Example 4 was repeated except that 0.19 grams of methanol per 100 grams of methoxybutene (6 equivalents per 100 equivalents) was added. The resulting data are presented in Table 1. Example 4 The procedure employed in Example 1 was repeated except that the toluene solvent was replaced with the halocarbon HCFC-123 (CHC1 2 CF 3 ). The resulting data are presented in Table 1. Example 7 The procedure employed in Example 5 was repeated except that the aqueous HI promoter was replaced with an equivalent amount of A1I 3 (2 equivalents of A1I 3 per g-atom of Rh). The resulting data are presented in Table 1. Example 8 The procedure employed in Example 3 was repeated except that the toluene solvent was replaced with the halocarbon HCFC-113 (FCC1 2 CF 2 C1). The resulting data are presented in Table 1. Example 9 The procedure employed in Example 3 was repeated except that the toluene solvent was replaced with the halocarbon HCFC-113 (FCC1 2 CF 2 C1) and the aqueous HI promoter was replaced with an equivalent amount of Til 4 (2 equivalents of Til 4 per g-atom of Rh). The resulting data are presented in Table 1. Table 1 Example Solvent Iodide MeOH Conversion Select Promoter per 100 meq to iV (6I/Rh) substrate 3 Toluene aq HI 0 94.0 84.8 4 Toluene aq HI 2 93.7 87.0 5 Toluene aq HI 6 94.0 83.5 6 HCFC-113 a HI 0 95.8 94.8 7 Toluene A1I 3 6 80.8 97.2 8 HCFC-113 aq HI 0 95.4 91.2 9 HCFC-113 Til 4 2 17.8 67.6 Examples 10-15 The procedure employed in Example 3 was repeated for a series of six additional runs except that the iodide promoter was varied and the resulting product was esterified with methanol to determine total carbonylation selectivity including dibasic esters (DBE's; esters of adipic acid, 2- methylglutaric and ethylsuccinic acids). The results are summarized in Table 2. Table 2 Example Iodide I/Rh Conversion Selectivity Selectivity Selectivity Promoter to M3P to M2P DBE's 10 arm * , HI 3 33.2. 95.9 0 1.9 11 aq HI 3 22.1 94.9 1.3 1.4 12 aq HI 3 7.2 100 0 0 13 aq HI 3 22.0 94.0 0 1.6 14 AII 3 3 97.2 10.1 53.3 36.6 15 aq HI 3 31.2 96.4 0 1.4 anhydrous HI in Acetic acid Example 16 Carbonylation of butadiene in the presence of methanol using a Rhodium Catalyst and aqueous HI Promoter: A 25 mL glass lined pressure vessel was charges with 5 mL of a solution containing 5.4 grams (100 mmol) of butadiene, 1.34 grams (6.0 mmol) of 57% aqueous HI, 3.2 grams methanol (100 mmole), 0.258 grams (1.0 mmol) of dicarbonylacetylacetonate rhodium(I), and 1.00 grams of o-dichlorobenzene (internal gas chromatograph standard) in 100 mL of toluene. The pressure vessel was freed from air by purging first with nitrogen (twice) and then with carbon monoxide containing 10 mol% hydrogen (twice). The vessel was then pressurized to 500 psig of 90/10 CO/H 2 and heated to 120 °C with agitation for 3 hours. The heat was shut off, the pressure vessel was allowed to cool to room temperature and the excess gases were vented. The product solution was analyzed directly by gas chromatography on a DBFFAP 30 M J&W Scientific capillary GC column. The results of the analysis are summarized below in Table 3. Examples 17-27 The procedure employed in Example 16 was repeated for a series of eleven additional runs except that the iodide promoter, the temperature, and the solvent were varied. The results are summarized in Table 3. Table 3 Example Temp. Solvent Iodide I/Rh Conversion Selectivity (°C) Promoter to M3P 16 120 Toluene aq HI 6 59.6 22.0 17 120 Toluene A1I 3 6 74.2 46.6 18 120 HCFC-123 aq HI 6 60.6 44.5 19 120 HCFC-123 A1I 3 6 83.0 32.7 20 140 Toluene A1I 3 6 85.7 58.1 Table 3 (continued) Exampl e Temp. Solvent Iodide I/Rh Conversion Selectivity 21 140 HCFC-123 A1I 3 6 87.5 47.7 22 120 Toluene anh HI 3 62.9 28.0 23 120 Toluene A1I 3 3 69.2 39.8 24 120 Toluene Snl 4 6 52.6 19.3 25 120 Toluene Crl 3 3 53.7 33.0 26 120 Toluene Til 4 3 63.6 41.8 27 120 Toluene aq HI 3 60.5 29.8 The process of the present invention is useful for the preparation of beta-gamma unsaturated carboxylic acid esters and in particular the production of methyl-3-pentenoate by the carbonylation of methyl crotyl ether, 3-methoxybutene-l and their mixtures or directly from a mixture of butadiene and methanol. Such products are useful as difunctional monomers and as intermediates in the synthesis of adipic acid. Having thus described and exemplified the invention with a certain degree of particularity, it should be appreciated that the following claims are not to be so limited but are to be afforded a scope commensurate with the wording of each element of the claim and equivalents thereof.

Claims: CLAIM OR CLAIMS I claim: 1. A process for the carbonylation of allylic butenyl ether or mixture of butadiene and an alcohol and the production of beta-gamma unsaturated carboxylic acid ester comprising the steps of: (a) reacting an allylic butenyl ether or mixture of butadiene and an alcohol with carbon monoxide in the presence of a rhodium-containing catalyst and an iodide-containing promoter; and (b) recovering a beta-gamma unsaturated carboxylic acid ester. 2. The process of Claim 1 wherein said allylic butenyl ether is selected from the group consisting of methyl crotyl ether, 3-methoxybutene-l and mixtures thereof and said beta-gamma unsaturated carboxylic acid ester is methyl-3 -pentenoate . 3. The process of Claim 1 wherein said carbonylation involves reacting butadiene and methanol and said beta-gamma unsaturated carboxylic acid ester is methyl-3-pentenoate. 4. The process of Claim 2 or 3 wherein said iodide-containing promoter is selected from the group consisting of HI, A1I 3 , Snl 4 , Til 4 , Crl 3 , and CoI 2 and said rhodium-containing catalyst is dicarbonylacetylacetonate rhodium(I).

Inventors: BURKE PATRICK MICHAEL, BURKE, PATRICK, MICHAEL
Applicants: DSM NV, DU PONT, DSM N.V., E.I. DU PONT DE NEMOURS AND COMPANY
Application year: 1999
Main classification: C07C67
IPC codes: C07B61, C07C67, C07C69