Studies on 6-[(Dimethylamino)methylene]aminouracils: a Facile One-pot Synthesis of Pyrimido[4,5-d]pyrimidines and Pyrido[2,3-d]pyrimidines. - Thakur, Ashim J; Saikia, Promod; Prajapati, Dipak; Sandhu, Jagir S (Synlett, 2001)