Facile synthesis of 6-aryl-1,3-dimethyl-5H-pyrimido-[4,5-b][1,4]diazepine-2,4(1H,3H)-diones

Article abstract of DOI:10.1135/cccc19990313

A facile procedure for the preparation of 6-aryl-1,3-dimethyl-5H-pyrimido[4,5-b][1,4]diazepine-2,4(1H,3H)-diones 8, 9 from 6-amino-5-arylideneamino-1,3-dimethyluracils 1, 2 and triethyl orthoacetate (3) in a two-step reaction via 6-aryl-8-ethoxy-6,7-dihydro-1,3-dimethyl-5H-pyrimido[4,5-b][1,4]diazepine-2,4(1H ,3H)-diones 6, 7 is described. Condensation of 1 with diethoxymethyl acetate (10) resulted in the formation of (1,3-dimethyl-2,6-(1H,3H)-dioxopurin-7-yl)(phenyl)methyl acetate (11) and a small amount of 1,3-dimethyl-6-phenyl-pyrazino[2,3-d]pyrimidine-2,4(1H,3H)-dione (12). The structures of 6 and 11 were unambiguously confirmed by single-crystal X-ray diffraction analysis.