Synthesis of Quinazoline Skeleton by the Aza-Wittig Reaction Followed by Various Cyclizations

The intermolecular version has been utilized for various heterocyclic syntheses including quinazoline ring via initial imine formation followed by electrocyclization, cycloaddition, and nucleophilic cyclization, etc. as developed by Molina (tandem aza-Wittig/cyclization strategy) [115], Saito (aza-Wittig/electrocyclization method) [125,126] and Wamhoff (three-component reaction) [112]. These general principles include pyrimido annulation as summarized in Scheme 1. Following these general strategies, a number of quinazoline derivatives such as dihydroquinazolines (29a,b) [126], (30a-c) [127], quinazolin-4-one derivatives (31a,b) [128], (32a,b,c) [128,129], (32a) [130,131], and 33 [132-135] are synthesized starting from anthranilic acid derivatives or the corresponding iminophosphorane or the pyrimidine derivative (I) (Fig. 3).



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