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.
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.
Johnston
Jeffrey N.
JN
Evans Chemical Laboratories, The Ohio State University, Columbus, Ohio 43210.
Tsui
Hon-Chung
HC
Paquette
Leo A.
LA