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 and propargylsilanes. Treatment of these allene containing lactams and oxazolidinone with allyl halides or an allyl carbonate using Pd(II)-salts as the catalyst gave rise to a coupling-cyclization reaction, yielding bicyclic systems in which the allyl moiety is incorporated. With this methodology several substituted pyrrolizinones, an oxazolone and indolizinone were prepared. (C) 2001 Elsevier Science Ltd. All rights reserved.