Cyclic B-ketoe sters, available by regioselective acylation of cycloalkanone enolates, are rapidly transformed to a,B-unsaturated acids. This functionality transposition allows the derived 3-hydroxy-4-methylthiazole-2- (3H)-thione derivatives to serve as precursors to synthetically useful vinyl bromides. The process involves heating the hydroxamate ester with AIBN in bromotrichloromethane solution. Alkylative and ring contractive variants of the methodology are highlighted. The short sequence makes available precursors to vinyl anions that are not otherwise conveniently accessible.
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