Application of an S --> O Allylic Transposition in the Context of a Bridgehead Olefinic System. New Opportunities for the Structural Modification of Bicyclo[6.2.1]undecanes via Transannular Ring Closure

J Org Chem. 1998 Jan 9;63(1):129-136. doi: 10.1021/jo971591n.

Abstract

A practical route is described for the preparation of allylic sulfide 8, whose double bond resides at a bridgehead site. Following hydride reduction of the ketone carbonyl and sulfoxidation, exposure to trifluoroacetic anhydride results in the operation of an intermolecular S --> O allylic transposition. This central step leads to 14a, an intermediate useful for probing the consequences associated with epoxidation of its cis-cyclononene double bond. A total of three different transannular cyclizations are described in order to demonstrate the ease with which ring closures can operate in a medium-ring setting of this type. Represented are transformations that generate tetrahydrofuran, oxetane, and cyclopropane subunits. The kinetic biases favoring these transformations are highlighted.