Activation of elemental sulfur by electrogenerated cyanomethyl anion: synthesis of substituted 2-aminothiophenes by Gewald reaction.

The activation of elemental sulfur (S8) has been achieved by means of electrogenerated cyano- methyl anion [easily obtained by galvanostatic reduc- tion from acetonitrile/tetraethylammonium hexa- fluorophosphate (MeCN-Et4NPF6)] . The “activated” sulfur reacted with ylidenemalononitriles to give sub- stituted 2-aminothiophenes in very high yields. This variation of the Gewald reaction has been carriedout using only catalytic amounts of electricity and supporting electrolyte. A proposed mechanism for the interaction between S8 and cyanomethyl anion is described.