Approaches to fused pyrimidine derivatives by the pyrimidine ring construction and their application to synthesis of purines

Fused pyrimidines can be easily synthesized from the corresponding ortho-am inobenzylamine derivatives or their heteroanalogues. ortho-Nitrobenzaldehyd es, ortho-aminobenzaldehydes, anthranilic. acid derivatives, ortho-isocyana tobenzoates, ortho-aminobenzonitriles, ortizo-isocyanatobenzonitriles, IV-s ubstituted anilines, ortho-halobenzoates, benzenediazonium salts, (2-nitroa ryl)methylisocyanides, and derivatives of the all above compounds were also used for this purpose. Often the limiting factor for the above syntheses i s the difficulty encountered in obtaining the key intermediates or their pr ecursors. Recently, this problem was successfully solved in several ways by the use of Vicarious Nucleophilic Substitution of Hydrogen (VNS). As a res ult, many quinazolines and newbicyclic and tricyclic heteroaromatic compoun ds and their mono-M-oxides were obtained, when starting from aromatic nitro compounds. These approaches were also successfully applied to the synthesi s of purines with the use of 4-nitroimidazole derivatives.