The Synthesis of Bridged and Fused Ring Carbocycles Using a Novel Variation of an Intramolecular Nicholas Reaction

Abstract

A novel variation of an intramolecular Nicholas reaction is described that provides an efficient method for the synthesis of fused and bridged bicyclic compounds. The mechanism appears to involve an initial regioselective in situ double bond migration of a terminal alkene. The more stable disubstituted alkene then undergoes an intramolecular cyclisation reaction with a dicobalt hexacarbonyl stabilised cation. This transformation generates a second cation, which is subsequently quenched by a halide ion derived from the Lewis acid.