Regiospecific one-pot synthesis of pyrimido[4,5-d]pyrimidine derivatives in the solid state under microwave irradiations

Electron rich 6-[(dimethylamino)methylene]amino uracil 1, undergoes [4+2] cycloaddition reactions with various in situ generated glyoxylate imine and imine oxides 6 to provide novel pyrimido[4,5-d]pyrimidine derivatives of biological significance, after elimination of dimethylamine from the (1:1) cycloadducts and oxidative aromatisation. This procedure provides a convenient method for the direct synthesis of pyrimido[4,5-d]pyrimidines in excellent yields when carried out in the solid state and under microwave irradiations.