Synthesis of cyclic allenylsilanes via an intramolecular substitution reaction of 1-siloxy-2,3-epoxyalkanes

Intramolecular substitution reactions of 1-(alkynylsiloxy)-2,3-epoxyalkanes under acidic or basic conditions were investigated. In the presence of t-butyllithium, cyclic allenylsilanes, which can be easily converted to the corresponding allenes, were obtained in good yields. The regioselectivity was highly dependent on the configuration of the epoxide moiety, which was rationalized by assuming chair-like transition state models of the 6-endo type cyclization reactions.