GENERATION AND INTRAMOLECULAR CYCLIZATION OF ALPHA-PHENYLSULFENYL ANDALPHA-ALKYLSULFENYL RADICALS

alpha-Phenylsulfenyl radicals are generated by the reaction of dipheny l dithioacetals or phenyl alpha-chlorosulfides with tributyltin hydrid e. Alkyl phenyl dithioacetals react selectively with tributyltin hydri de to give alpha-alkylsulfenyl radicals. 5-Exo-type of intramolecular cyclizations of these radicals are studied. The cyclization is most su ccessful when the olefin is terminally substituted with an ester group . The cis/trans ratio of the cyclized product varies according to the reaction rates. With a faster cyclization, cis-isomer is the major pro duct. A slower cyclization gives more trans-product. (C) 1997 Elsevier Science Ltd.