N-Acyliminium ion chemistry and palladium catalysis: a useful combination to obtain bicyclic heterocycles

By using N-acyliminium ion chemistry, several omega -propadienyllactams and a propadienyloxazolidine were prepared from N-acyliminium ion precursors a nd propargylsilanes. Treatment of these allene containing lactams and oxazo lidinone with allyl halides or an allyl carbonate using Pd(II)-salts as the catalyst gave rise to a coupling-cyclization reaction, yielding bicyclic s ystems in which the allyl moiety is incorporated. With this methodology sev eral substituted pyrrolizinones, an oxazolone and indolizinone were prepare d. (C) 2001 Elsevier Science Ltd. All rights reserved.