N-alkenyl nitrone dipolar cycloaddition routes to piperidines and indolizidines .8. the scope of tandem reactions involving hydroxylamine-alkyne cyclisations

A tandem sequence of hydroxylamine-alkyne cyclisation/1,3-dipolar cycloaddition, provides useful entry into tricyclic systems of type 4. The scope of such reactions is explored in this paper. A novel cascade cyclisation of N-hydroxypyrrolidines of type 26 and 28 involving hydroxylamine-alkyne cyclisation, Cope elimination and 1,3-dipolar cycloaddition is also reported. Copyright (C) 1996 Elsevier Science Ltd