Synthesis of Quinazolin-4(3H)-ones via Amidine N-Arylation

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 PhBCl2. 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.