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Paper | Regular issue | Vol 68, No. 2, 2006, pp.295-306
Published online, 17th January, 2006
DOI: 10.3987/COM-05-10629
A Facile Synthesis of Substituted 1,8-Naphthyridines Based on the Aza-Wittig/Electrocyclic Ring Closure Strategy

Carmen Veiga, José Ma Quintela,* Carlos Peinador,* Marcos Chas, and Antonio Fernández

*Department of Fundamental Chemistry, Faculty of Sciences, University of A Coruña, Campus A Zapateira, E-15071, A Coruña, Spain

Abstract

Several new 1,8-naphthyridine derivatives (7) and (8) has been synthesized via an aza-Wittig reaction. Iminophosphoranes, 2-ethoxy-3-cyano-5-(2-ethoxycarbonyl)-4-phenyl-6-[(triphenylphosphoranilidene)amino]pyiridine (4) and 2-ethoxy-3-cyano-5-(2-cyanovinyl)-4-phenyl-6[(triphenylphosphoranilidene)- amino]pyridine (5), easily obtained from the 2-chloro-5-cyano-6-ethoxy-4-phenylpyridine-3-carboxaldehyde (1), react with heterocumumulenes such as aromatic isocyanates to give directly the title compounds in an aza-Wittig/electrocyclic ring closure process. The yields were from 60% to 97%.