Carboalkoxylation

In industrial chemistry, carboalkoxylation is a process for converting alkenes to esters. This reaction is a form of carbonylation. A closely related reaction is hydrocarboxylation, which employs water in place of alcohols.

A commercial application is the carbomethoxylation of ethylene to give methyl propionate:^[1]

C₂H₄ + CO + MeOH → MeO₂CC₂H₅

The process is catalyzed by Pd[C₆H₄(CH₂PBu-t)₂]₂. Under similar conditions, other Pd-diphosphines catalyze formation of polyethyleneketone.

Methyl propionate ester is a precursor to methyl methacrylate, which is used in plastics and adhesives.^[2]

Carboalkoxylation has been incorporated into various telomerization schemes. For example carboalkoxylation has been coupled with the dimerization of 1,3-butadiene. This step produces a doubly unsaturated C9-ester:^[3][4]

2 CH₂=CH−CH=CH₂ + CO + CH₃OH → CH₂=CH(CH₂)₃CH=CHCH₂CO₂CH₃

Hydroesterification

Related to carboalkoxylation is hydroesterification, the insertion of alkenes and alkynes into the H-O bond of carboxylic acids. Vinyl acetate is produced industrially by the addition of acetic acid to acetylene in the presence of zinc acetate catalysts:^[5] Presently, zinc acetate is used as the catalyst:

CH₃CO₂H + C₂H₂ → CH₃CO₂CHCH₂

Further reading

• Schoenberg, A.; Bartoletti, I.; Heck, R. F. (1974). "Palladium-catalyzed carboalkoxylation of aryl, benzyl, and vinylic halides". The Journal of Organic Chemistry. 39 (23): 3318–3326. doi:10.1021/jo00937a003.