Lewis acid mediated cascade reactions of silyl-substituted methylenecyclopropyl ketones

The Lewis acid mediated cyclisation of various silyl-substituted methylenecyclopropyl ketones has been investigated. The presence of the silyl-substituent enhances the reactivity of the methylene cyclopropane in comparison to our earlier study on non-silyl-substituted methylenecyclopropyl ketones, allowing milder Lewis acids (BF3·Et2O or BF3·2AcOH) to be used for the cyclisation reaction. The mild conditions used allow the allyl cation, formed as an intermediate in the cyclisation, to be trapped in further carbon–carbon bond-forming reactions.