A novel microwave-assisted one-pot synthesis of pyrano[2,3-d]pyrimidines and pyrido[2,,3-d]pyrimidines via a three component reaction in solvent-free condition

Three-component cyclocondensation of barbituric acids 1, triethylorthoformate. 2 and alkyl nitriles 3 in presence of acetic anhydride proceeds under microwave-assisted conditions to give pyrano[2,3-d]pyrimidines 4 in excellent yields. 6-Aminouracils 5 or 6-hydroxy-aminouracils 7 react with 2 and 3 under identical conditions to yield pyrido[2,3-d]pyrimidines 6 or pyrido[2,3-d]pyrimidine oxides 8 in high yields.