Synthesis of amidine and bis amidine percursors

The reactions of substituted o-phenylene diamines, o-aminophenol, o-aminoth iophenol, 3,4-diaminopyridine with p-cyanobenzaldehyde by refluxing in nitr obenzene gave corresponding benzimidazole, benzoxazole, benzthiazole and im idazopyridine derivatives Ia,b, II, III, and IV, respectively. Reaction of 4,5-diaminopyrimidine with p-cyanobenzaldehyde gave only Schiffs base i.e. V or V' and not imidazopyrimidine derivative. 2,6-Pyridine dialdehyde on co ndensation with p-aminobenzonitrile gave corresponding dicyano compound VI. In an attempt to couple p-aminobenzonitrile with 2,6- pyridine dicarboxyli c acid using dicyclohexyl carbodiimide or 1, 1'-carbonyl diimidazole, only intermediates VI I & VIII were obtained, respectively and no coupled produc t was formed.