Photocyclisation of NN-dialkyl α-thioxoamides. Selective γ-hydrogen abstraction by the thiocarbonyl group

Abstract

NN-Di-isopropyl and NN-s-butyl-α-phenylthioxoacetamides (1a) and (1b) undergo γ-hydrogen-abstraction rather than δ-hydrogen abstraction on irradiation to give the corresponding β-lactams (2a) and (2b) respectively, while irradiation of NN-diethyl-α-phenylthioxoacetamide (1c) yields the disulphide (3c); the selective γ-hydrogen abstraction may be explained in terms of an electron transfer mechanism.