Radikalische Cyclisierungen von Alkenyl‐substituierten 4,5‐Dihydro‐1,3‐thiazol‐5‐thiolen

Radical Cyclizations of Alkenyl‐Substituted 4,5‐Dihydro‐1,3‐thiazole‐5‐thiols 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 me CS group of 1,3‐thiazole‐5(4 H )‐thiones with Grignard ‐reagents or alkylcuprates. The thiazolethiones were obtained by the reaction of 3‐amino‐2 H ‐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 ).