Steric Stabilization of Nucleophilic Carbenes

Abstract

Two tert-butyl groups at the nitrogen atoms of the cyclic carbene 2, which is accessible from 1 by reduction with potassium, provide sufficient stability to enable it to be stored indefinitely under exclusion of air and moisture. In contrast, sterically less shielded carbenes of type 2 (R = Me, Et, iPr) dimerize slowly at room temperature to olefins 3.