A facile microwave induced one-pot synthesis of novel pyrimido[4,5-d]pyrimidines and pyrido[2,3-d]pyrimidines under solvent-free conditions

Electron rich 6-[(dimethylamino)methylene]aminouracil 1, undergoes [4+2] cycloaddition reactions with various electron deficient substrates to give pyrimido[4,5-d]pyrimidines and pyrido[2,3-d]pyrimidines, after elimination of dimethylamine from the (1:1) cycloadducts and oxidative aromatisation. The reaction gives excellent yields when carried out under microwave irradiation under solvent-free conditions.