Abstract: The acid-catalyzed cyclocondensation of N, N'-bisaryl (aryl= 2-pyrimidinyl, 2- pyrazinyl and 4-nitrophenyl) methanediamines 5a-c with aqueous formaldehyde in refluxing acetonitrile leads to the formation of the corresponding 1, 3, 5-triaryl-1, 3, 5-hexa- hydrotriazines 6a-c. The stoichiometric reactions of 2-aminopyrimidine and 2-amino- pyrazine with aqueous formaldehyde in acetonitrile under reflux conditions also afforded ...