Radical Cyclizations of Alkenyl-Substituted 4,5-Dihydro-1,3-thiazole-5-thiols

Article abstract of DOI:10.1002/hlca.19890720425

Heating of 5-alkenyl- or 5-alkinyl-4,5-dihydro-1,3-thiazole-5-thiols of type 5 in the presence of a radical initiator gave dithiaspirobicycles in fair-to-excellent yield (Scheme 3).Under analogous conditions, the 4,5-dihydro-4-vinyl-1,3-thiazole-5-thiol 5d underwent a cyclization to give the annellated dithiabicycle 7 (Scheme 4).In this reaction, a minor product 8 was formed by an unknown reaction mechanism.The structure of 8 was established by X-ray crystallography.The starting 1,3-thiazole-5-thiols 5 have been synthesized by carbophilic alkylation of the C=S group of 1,3-thiazole-5(4H)-thiones with Grignard-reagents or alkylcuprates.The thiazolethiones were obtained by the reaction of 3-amino-2H-azirines with thiobenzoic acid followed by sulfurization and cyclization.The 4-benzyl derivative 1b was thermally rearranged via 1,3-benzyl migration to yield the benzyl (1,3-thiazol-5-yl) sulfide 11 (Scheme 5).