Application of iminophosphorane in heterocyclic synthesis

Abstract

Recent work of our group on the synthesis of heterocycles via aza-Wittig reaction of iminophosphorane was reviewed. We have developed a new efficient synthesis of various imidazolones or oxazoles by utilizing a consecutive cyclization of α-ethoxycarbonyl iminophosphorane, isocynate (or carbon disulfide) and various nucleophilic reagents. New derivatives of (fused) quinazolinones and pyrimidinones were prepared from the tandem reaction of β-ethoxycarbonyl iminophosphorane, isocynate (or carbon disulfide) and various nucleophilic reagents. Indole derivatives were also obtained in good yields from the sequential reaction of β-phenylethynyl iminophosphorane, isocynate and various nucleophilic reagents in the presence of a catalytic amount of Ag+. Recently the iminophosphorane was applied in post-condensation modifications of Ugi and Passerini reactions to prepare multisubstituted benzoxazines and quinazolines.