THE SCOPE AND LIMITATIONS OF INTRAMOLECULAR RADICAL CYCLIZATIONS OF ACYLSILANES WITH ALKYL, ARYL, AND VINYL RADICALS

5-Exo cyclizations of primary and secondary radicals with acylsilanes successfully give cyclopentyl silyl ethers. The corresponding 6-exo cy clizations are sensitive to changes of the size of silyl groups. Secon dary radicals undergo 6-exo cyclizations with acylsilanes more slowly. Reaction of aryl radical with acylsilane proceeds well for 5-exo cycl ization but not for 6-exo cyclization. Vinyl radicals give best result s in 5-exo cyclizations with acylsilanes but give low yields (similar to 30%) in 6-exo cyclizations. Intramolecular cyclizations of vinyl ra dicals with acylsilanes give enol silyl ethers regiospecifically.