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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

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journal contribution
posted on 09.01.1998 by Jeffrey N. Johnston, Hon-Chung Tsui, Leo A. Paquette
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.