Stereoselective electrophile-induced mono- and bis-cyclisation-fragmentation reactions of alkenyl oxime O-allyl and O-benzyl ethers. Synthesis of dihydropinidine

摘要

Phenylseleny bromide-induced cyclisation of gamma- and delta-unsaturated aldoxime and ketoxime O-allyl and O-benzyl ethers is followed by a slow fragmentation of the resultant oxyiminium ions furnishing cyclic iminium salts which are readily reduced to pyrrolidines, piperidines or tetrahydroisoquinolines by sodium borohydride; dialkenyl oximes yield indolizidines and quinolizidines by an analogous sequence terminating in a mercury(II)-induced cyclisation. (C) 2002 Elsevier Science Ltd. All rights reserved. [References: 37]