5,5-Disubstituted pyrrolidinones and 5-substituted pyrrolidinones were obtained with moderate to good diastereoisomeric excess through the cis addition of allyltributyltin and triethylsilane, respectively, to the 4-OTBS group in the N-acyliminium ion prepared from the corresponding 5-hydroxy lactams. Cyclization of an N-allyl-5-propargyl pyrrolidinone and N-allyl-5-allyl-5-substituted pyrrolidinones using Grubbs' catalyst led to the preparation of a dehydropyrre lizinone and dehydroindolizinones containing a quaternary stereocenter. (C) 2000 Elsevier Science Ltd. All rights reserved.113753764