Iron( III ) mediated transformations of cyclopropyltrimethylsilyl ethers. Part 1. Free radical tandem ring expansion–cyclisation reactions for the rapid construction of [n.3.0] bicyclic ring systems

Treatment of a number of [n.1.0] cyclopropyl trimethylsilyl ethers with anhydrous ferric chloride in dry dimethylformamide leads to diastereoisomerically pure [n.3.0] bicyclic chloro ketones by a novel tandem ring expansion–cyclisation sequence. The reaction is thought to proceed by a mechanism involving the intermediacy of a cyclopropyl alkoxy radical.