Pyrimidines. 21. Novel reactions of 5-cyano-1,3-dimethyluracil with carbon nucleophiles. A facile preparation of certain pyrido[2,3-d]pyrimidines

摘要: Treatment of 5-cyano-1,3-dimethyluracil (8) with an activated acetonitrile, such as malononitrile, ethyl cyanoacetate or cyanoacetamide, in base afforded 7-amino-6-cyano-, 7-amino-6-ethoxycarbonyl-, and 7-amino-6-aminocarbonyl-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4(1H,3H)-dione (18b, 18c 18d, respectively) high yields. On the other hand, reaction 8 acetonitrile gave Michael adduct, 5-cyano-6-cyanomethyl-5,6-dihydrouracil (15, R = H), hydrated product, 1,3-dimethyluracil-5-carboxamide (9) major products, 7-amino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4(1H,3H)-dione (18a) only very low yield. Similar butanone 7-ethyl-1,3-dimethyl- 1,3,6,7-tetramethylpyrido[2,3-d]pyrimidine-2,4(1H,3H)-dione (10b 10c) yields. When was treated diethylmalonate base, a small amount 6-ethoxycarbonyl-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4,7(1H,3H,8H)-trione (19) obtained together 1,3-dimethylpyrido[2,3-d]pyrimidine-2,4(1H,3H)-dione (20) (also yields). ethanolic sodium ethoxide without added carbon nucleophile significant amounts (14%) 20 18c.