CARBODIIMIDE-SULFOXIDE REACTIONS .7. SYNTHESIS OF STABILIZED SULFONIUM YLIDES

A wide range of compounds containing reactive methylene groups flanked by carbonyl, ester, nitrile, amide, and phosphonate groups have been treated with dicyclohexylcarbodiimide and dimethyl sulfoxide, or other sulfoxides, in the presence of anhydrous phosphoric acid. The products from these reactions have been isolated in crystalline form and characterized as highly stabilized sulfonium ylides. The nuclear magnetic resonance spectra of certain of these ylides provide striking examples of magnetic nonequivalence of aliphatic methylene groups. Possible mechanisms of the reaction are discussed, and the X-ray crystallographic structure of one ylide is presented. © 1968, American Chemical Society. All rights reserved.