STEREOCONTROL IN INTERMOLECULAR NUCLEOPHILIC ADDITION TO N-ACYLIMINIUM ION DIRECTED BY A BICYCLO[2.2.1]HEPTENE OR 7-OXABICYCLO[2.2.1]HEPTENE GROUP. A NOVEL ROUTE TO 5-SUBSTITUTED 3-PYRROLIN-2-ONES OF HIGH OPTICAL PURITY

Abstract

Intermolecular nucleophilic additions to the conformationally rigid, tricyclic pyrrolidinium ion (derived from 2 or 6) took place exclusively from the less-hindered face fused with its bicyclo[2.2.1]heptene or 7-oxabicyclo[2.2.1]heptene moiety. Retro-Diels-Alder fragmentation of the resulting chiral 7-oxabicyclo[2.2.1]heptene system furnished a 5-substituted 3-pyrrolin-2-one without a loss of optical purity.