Multigram scale cobalt catalyzed photochemical methoxycarbonylation of alkenes

Photocarbonylation of alkenes was successfully carried out on a multigram scale (5-10 g) on a number of alkenes. Optimum conditions (temperature, solvent, concentration, UV source and filters) were established; it was shown that the rate of reaction depends on the concentration of the cobalt catalyst. The cobalt catalyst was stable only under a narrow range of conditions and any deviation from them either reduced the rate of photocarbonylation, or caused the cobalt to precipitate and stop the reaction. It was shown that the rate and selectivity of photocarbonylation reaction depend on a degree of substitution of alkenes. Mono and disubstituted alkenes gave the corresponding methyl esters in good yields (69-85%), while trisubstituted alkenes either did not react at all, or gave complex mixtures of products. Selectivity can be achieved in carbonylation of dienes if conversion is kept low. (C) 2001 Elsevier Science B.V. All rights reserved.