Stereospecific and regioselective isocyanide insertions into siliranes andreactions of the resulting iminosilacyclobutanes

The insertions of p-tolyl and tert-butyl isocyanide into siliranes yielded iminosilacyclobutanes with stereospecific retention of configuration. Monos ubstituted siliranes underwent insertion into the more substituted Si-C bon d of the ring, although this regioselectivity was eroded as substitution in creased on the silirane ring. The iminosilacyclobutane products tautomerize d thermally or in the presence of a palladium catalyst to yield the thermod ynamically more stable aminosilacyclobutenes. Ring-expansion reactions of i minosilacyclobutanes were promoted by acids: treatment with aqueous copper sulfate produced an oxasilacyclopentane in high yield, whereas with trifluo roacetic acid, oxasilacyclohexanes were formed.