A simple approach for the regioselective synthesis of imidazo[1,2-a]pyrimidiones and pyrimido[1,2-a]pyrimidinones

Several imidazo and pyrimido[1,2-a]pyrimidinones of type and were synthesized through intramolecular cyclization of pyrimidines or pyrimidinones bearing a variety of β and γ-aminoalcohols at the 2-position. Ring closure of the pyrimidinones of type under Mitsunobu conditions lead to mixtures of both bicyclic regioisomers and . Treatment of pyrimidines of type with H2SO4 provided an efficient and operationally simple one-pot hydrolysis–cyclization procedure for obtaining imidazo and pyrimido[1,2-a]pyrimidinones in good yields as the sole regioisomeric bicyclic product.