Cycloaddition of New N-Unsubstituted Azomethine Ylides Generated from N-(Trimethylsilylmethyl)thioureas to Electron-Deficient Olefins, Acetylenes and Aldehydes, Synthetic Equivalents of Nonstabilized Aminonitrile Ylides

The S-methylation of N-(trimethylsilylmethyl)thioureas and the subsequent desilylation of the silylmethyl group generates N-unsubstituted azomethine ylides having both methylthio and amino groups at the ylide carbon. These azomethine ylides undergo successful cycloaddition to electron-deficient olefins, acetylenes and aldehydes. As the methylthio group is eliminated under the reaction conditions to produce the corresponding pyrrolines, pyrroles and 2-oxazolines bearing the amino group at 2-position, these azomethine ylides can be synthetic equivalents of nonstabilized aminonitrile ylides that are otherwise relatively inaccessible.