Ring transformation of 1,5‐diazabicyclo[3.1.0]hexanes under the action of arylketenes

Abstract

Abstract magnified image The reactions of 1,5‐diazabicyclo[3.1.0]hexanes 8 with arylketenes 1 have been studied in different conditions. The 1‐(arylacethyl)pyrazolidines 11 were obtained at −30 °C in ether and at 20 °C in benzene instead of the expected bicyclic systems 1,5‐diazabicyclo[3.2.1]octan‐6‐one 9 and 3‐aryl‐1,5‐diazabicyclo[3.3.0]octane‐2‐one 10 . The synthesis of two representatives of bicycles 10 ( 10a,b ) proceeded in the reaction of unsubstituted 1,5‐diazabicycle[3.1.0]hexane 8a , accordingly, with diphenylketene 1a in benzene at 20 °C and with 4‐chlorophenylketene 1b in toluene at 60‐110 °C. Mechanisms of the studied transformations were offered.