THE MECHANISM OF THE DIRECT PHOTO-OXIDATIVE DECARBOXYLATION OF α-OXOCARBOXYLIC ESTERS

Article abstract of DOI:10.1016/S0040-4020(01)91868-X

A variety of α-oxo-carboxylic esters are shown to undergo direct photo-oxidation, in both polar and non-polar solvents, to produce a higher yield of carbon dioxyde than under degassed conditions.In the case of n-hexyl pyruvate, hexaldehyde is also a product of the reaction.Evidence is presented which indicates that singlet oxygen plays little, if any, part in these decarboxylations.A mechanism involving electron transfer from the excited α-oxo-carboxylic ester to ground state oxygen, leading to per-acid intermediates, is proposed as being in competition with the TYpe II process for fragmentation of these esters.