Pyrido[4,3-d]pyrimidin-4(3H)-one (1) was prepared by reacting 2-trifluoromethyl-4-iodo-nicotinic acid (2) with amidine 9a catalyzed by Pd(2)(dba)(3) and Xantphos, followed by cyclization effected with HBTU and subsequent demethylation using PhBCl(2). The amidine arylation method was found applicable for the syntheses of quinazolin-4(3H)-ones. Thus, reaction of 2-bromo or 2-iodo benzoate esters with amdidines afforded substituted quinazolin-4(3H)-ones in 44-89% yields.