Thiyl radical-mediated cyclization of ω-alkynyl O-tert-butyldiphenylsilyloximes

ω-Alkynyl O-tert-butyldiphenylsilyloximes, upon treatment with odorless 4-tert-butylbenzenethiol in the presence of azobisisobutyronitrile (AIBN) in refluxing benzene, underwent addition of a thiyl radical to the alkynyl group followed by radical cyclization of the corresponding vinyl radical onto the O-silyloxime moiety to give cyclic O-silylhydroxylamines in good yields. The reactivity of O-silyloximes in radical cyclization was similar to or even higher than that of O-benzyloximes. Facile removal of the silyl group of the cyclization products leading to hydroxylamines and nitrone formation of the hydroxylamines were also demonstrated.