Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Patent
1997-09-16
2000-06-13
Richter, Johann
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C07C 6737
Patent
active
060751614
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for preparing 3-pentenoic esters by carbonylation of alkoxybutenes in the presence of a catalyst and a solvent at elevated temperature and elevated pressure.
EP-A 301 450 and EP-A 351 616 disclose processes for preparing alkyl pentenoates by reacting butadiene with carbon monoxide and alcohols in the presence of cobalt carbonyl complexes and tertiary nitrogen bases. These processes require high pressures of from 120 to 700 bar and form mixtures of 2-, 3- and 4-pentenoic esters.
GB-A 1 110 405 describes a process for preparing pentenoic esters by carbonylation of butadiene in the presence of an alcohol using platinum, palladium and/or nickel catalysts. Here too, high pressures of from 100 to 1000 bar are required.
EP-A 60 734 discloses a process for preparing pentenoic esters by carbonylation of butadiene in the presence of an alcohol, a hydrogen halide and a palladium catalyst at lower pressures around 150 bar. A disadvantage of this process is that a large excess of corrosive hydrogen halide is required (molar ratio of hydrogen halide to palladium is 20-100:1).
According to EP-A 284 170 and EP-A 271 145, pentenoic esters can be prepared by carbonylation of butadiene in the presence of alcohols using palladium compounds, phosphines and acids. This does not give the 3-pentenoic ester in pure form, but in admixture with its isomers.
Another way of preparing .beta.,.gamma.-unsaturated esters is described in U.S. Pat. No. 4,622,416. Carbonylation of allyl ethers catalyzed by nickel, cobalt or iron halides gives the esters. A disadvantage of this process is the formation of product mixtures. The carbonylation of 8-methoxy-1,6-octadiene gives not only methyl 3,8-nonadienoate but also three cyclic carboxylic acid compounds. Satisfactory selectivities (maximum 91%) can only be obtained at a pressure above 170 bar and a temperature of 150.degree. C. Under these conditions the catalyst loss resulting from formation of volatile nickel compounds is very high.
EP-A 217 407 describes the carbonylation of allyl ethers with PdCl.sub.2 /CuCl.sub.2 catalysis to give unsaturated esters. Here, large amounts of tetrabutylammonium chloride (25 mol % based on starting material) are added to the reaction mixture for extraction of the product. This addition leads to extensive precipitation of metallic palladium.
EP-A 514 288, EP-A 478 471 and EP-A 433 191 disclose the double carbonylation of 1,4-butenediols and 1,4-dialkoxybutenes to give dehydroadipic acid (diesters) using palladium compounds and chlorides such as alkali metal, alkaline earth metal or quaternary ammonium or phosphonium halides. These processes require a large excess of chloride (typical molar ratios of Pd to chloride of from 1:17 to 1:27) or else large amounts of PdCl.sub.2 of about 20 mol %, based on the starting material.
It is an object of the present invention to provide a process for preparing 3-pentenoic esters containing a very low proportion of isomeric 2- and 4-pentenoic esters by carbonylation of alkoxybutenes in the presence of a catalyst based on palladium under mild conditions.
We have found that this object is achieved by a process for preparing 3-pentenoic esters by carbonylation of alkoxybutenes in the presence of a catalyst and a solvent at elevated temperature and elevated pressure, by reacting at least one C.sub.1 -C.sub.10 -alkoxybutene in which the alkoxy group is in the allyl position relative to the double bond with carbon monoxide at from 60 to 140.degree. C. and a carbon monoxide partial pressure in the range from 3 to 30 MPa in the presence of a catalyst based on palladium.
In addition, we have found a homogeneous catalyst system in which no catalyst deactivation occurs as a result of palladium precipitation if the carbonylation is carried out in the additional presence of quaternary ammonium or phosphonium salts or specific phosphines.
The starting materials used in the process of the invention include at least one C.sub.1 -C.sub.10 -alkoxybutene, preferably a C.sub.1 -C.sub.4 -alkoxybutene, in
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Dictionary of Organom. Compounds, vol. 2, 1984, pp. 1484-1544.
Hohn Arthur
Langguth Ernst
Lippert Ferdinand
Schneider Regina
BASF - Aktiengesellschaft
Keys Rosalynd
Richter Johann
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