Reaction of cyanotrimethylsilane with oxiranes under the catalytic action of Lewis acids Pd (CN)*, SnC12, or MeaGa affords 2-trimethylsiloxy isocyanides by regio-and stereoselective attack of isocyanide on the more substituted carbon. The reaction mediated by aluminium alkoxides gives predominantly 3-trimethylsiloxy nitriles by the selective attack of cyanide on the less substituted carbon.