Francisco Ros
Reaction of 2-chloroisobutyrophenone with two equivalents of malononitrile anion furnishes 2-amino-1,3dicyano-5,5-dimethyl-4-phenylcyclopenta-1,3-diene. The cyclic compound represents the novel 2-amino-1,3dicyanocyclopentadiene structure. The unique 1-cyano-2-amino-3-cyano arrangement in the cyclopentadiene brings about a strong polarization of the electronic configuration of the diene system that is conformed by two opposite dipolar halves. The polarized electronic configuration accounts for the extreme persistence manifested by the cyclopentadiene. The compound owns a vivid lemon-hued yellow color consequent to an unusually intense n absorption of a cyano group in the extensively conjugated compound. This is built up by consecutive one-pot reaction of two molecules of malonon itrile carbanion and the ketonic substrate followed by a new tandem carbon-carbon cyclization with final elimination of cyanate ion.