X=Y–ZH Systems as potential 1,3-dipoles. Part 52: Fused-ring forming electrophile induced oxime→nitrone→cycloaddition cascades
作者:H Ali Dondas、Ronald Grigg、Sylvie Thibault
DOI:10.1016/s0040-4020(01)00661-5
日期:2001.8
Electrophileinducedcyclisation of oximes onto endocyclic alkenes and exo-methylene cycloalkanes occurs stereo- and regio-specifically generating cis-fused bicyclic nitrones in good yield. Subsequent facially selective cycloaddition with N-methylmaleimide occurs in good yield. The sequence may be carried out as a one-pot procedure and results in the formation of 4 bonds, 2 rings and 6 stereocentres
Stereoselective electrophile-induced mono- and bis-cyclisation–fragmentation reactions of alkenyl oxime O-allyl and O-benzyl ethers. Synthesis of dihydropinidine
作者:H Ali Dondas、Ronald Grigg、Jasothara Markandu、Trevor Perrior、Tekka Suzuki、Sylvie Thibault、W Anthony Thomas、Mark Thornton-Pett
DOI:10.1016/s0040-4020(01)01118-8
日期:2002.1
Phenylseleny bromide-induced cyclisation of γ- and δ-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
The potential of the oxy-Favorskii rearrangement to form branched cis-fused bicyclic ethers was explored. Both tertiary and quaternary centers were constructed in highly stereospecific manners. Methanol and primary amines were effective nucleophiles for the rearrangement. The total synthesis of (±)-communiol E was achieved based on this method.