Photochemistry of Phthaloylcsteine, its methyl ester and C-unprotected S-Alkyl derivatives

Article abstract of DOI:10.1016/S0040-4020(98)00063-5

N-Phthaloyl cysteine derivatives 1a-d were photochemically transformed by elimination, decarboxylation, and via electron transfer cyclization to the products 2,3,4 and 6-8. The spin selectivities of the singlet and triplet pathways were investigated in acetonitrile and acetone . The excited singlets were prone to elimination and γ-H abstraction (e.g. formation of 5) whereas the triplets cyclized to thiazinoisoindoles. This behavior can be correlated with efficiencies of forward and return electron transfer stepsversus homolytic hydrogen abstraction as exemplified for the cysteine substrate.