α-ACYLIMINIUM ION-ACETYLENE CYCLISATIONS

Article abstract of DOI:10.1016/0040-4020(80)85036-8

Cyclisation of acetylenic ethoxylactams 1b-12b leads to bridgehead nitrogen bicyclic ketones in excellent yields.The reaction is weakly acid-catalysed and proceeds at ambient temperature.The observed regioselectivity effect is discussed in terms of stability of exo vs endo vinyl cations and ring strain effects.The high yield conversion of N-(5-hexynyl)-ethoxy lactams 7b and 8b in the 5/8 and 6/8 fused bicyclic ketolactams 7c and 8c deserves special attention.