The Scope and Limitations of Intramolecular Radical Cyclizations of Acylsilanes with Alkyl, Aryl, and Vinyl Radicals

Abstract

5-Exo cyclizations of primary and secondary radicals with acylsilanes successfully give cyclopentyl silyl ethers. The corresponding 6-exo cyclizations are sensitive to changes of the size of silyl groups. Secondary radicals undergo 6-exo cyclizations with acylsilanes more slowly. Reaction of aryl radical with acylsilane proceeds well for 5-exo cyclization but not for 6-exo cyclization. Vinyl radicals give best results in 5-exo cyclizations with acylsilanes but give low yields (∼30%) in 6-exo cyclizations. Intramolecular cyclizations of vinyl radicals with acylsilanes give enol silyl ethers regiospecifically.