Branched 2-amino-1, 3-dicyanocyclopenta-1, 3-diene

Reaction of 2-chloroisobutyrophenone with two equivalents of malononitrile anion furnishes 2-amino-1,3-dicyano-5,5-dimethyl-4-phenylcyclopenta-1,3-diene. The cyclic compound represents the novel 2-amino-1,3-dicyanocyclopentadiene structure. The unique 1-cyano-2-amino-3-cyano arrangement in a cyclopentadienic ring brings about a strong polarization of the electronic configuration of the diene pi system that is conformed by two opposite dipolar halves as revealed by IR and 13C NMR data for the compound. Such polarized configuration accounts for the extreme persistence manifested by the compound in contrast with unsubstituted cyclopentadiene. The cyclopentadiene owns a vivid lemon-hued yellow color consequent to an unusually intense n pi absorption of a cyano group in the extensively conjugated compound. It owns odd photophysical characteristics connected with the arrangement of amino and cyano groups in the diene ring. The compound is built up by consecutive one-pot reaction of two molecules of malononitrile carbanion and a ketonic substrate, and the reaction mechanism continues by a new type of tandem carbon-carbon cyclization that comprises a final elimination of cyanate ion. Reaction of 2-chloroisobutyrophenone with two equivalents of malononitrile anion furnishes 2-amino-1,3-dicyano-5,5-dimethyl-4-phenylcyclopenta-1,3-diene. The cyclic compound represents the novel 2-amino-1,3-dicyanocyclopentadiene structure. The unique 1-cyano-2-amino-3-cyano arrangement in a cyclopentadienic ring brings about a strong polarization of the electronic configuration of the diene pi system that is conformed by two opposite dipolar halves as revealed by IR and 13C NMR data for the compound. Such polarized configuration accounts for the extreme persistence manifested by the compound in contrast with unsubstituted cyclopentadiene. The cyclopentadiene owns a vivid lemon-hued yellow color consequent to an unusually intense n pi absorption of a cyano group in the extensively conjugated compound. It owns odd photophysical characteristics connected with the arrangement of amino and cyano groups in the diene ring. The compound is built up by consecutive one-pot reaction of two molecules of malononitrile carbanion and a ketonic substrate, and the reaction mechanism continues by a new type of tandem carbon-carbon cyclization that comprises a final elimination of cyanate ion.

Autorentext

Dr. Francisco Ros ist Wissenschaftler am Consejo Superior de Investigaciones Científicas (CSIC), Spanien. Seine Forschungsinteressen sind: Synthese und therapeutische Anwendungen von verzweigtkettigen organischen Verbindungen; thermodynamische Entropie und ihre Beziehung zur Zeit.