Convenient one-pot synthesis of N3-substituted pyrido[2,3-d]-, pyrido[3,4-d]-, pyrido[4,3-d]-pyrimidin-4(3H)-ones, and quinazolin-4(3H)-ones analogs

A convenient microwave-assisted one-pot sequential synthesis provided access to novel pyridopyrimidin-4-(3H)-ones in good to excellent yields. Anthranilic acid, 2- and 4-aminonicotinic acids, and 3-aminoisonicotinic acid were quantitatively converted into the analogous amidinoesters which undergo rapid cyclization in the presence of an amine.