2-取代-5,5-二硝基嘧啶-4,6-二酮的合成和反应

研究了2-取代嘧啶-4,6-二酮的硝化反应, 产物为2-取代-5,5-二硝基嘧啶-4,6-二酮(3), 收率＞80%, 3与亲核试剂反应形成开环产物. 2-位取代基为烷基时, 嘧啶环5-位和侧链的α-位都发生反应, 当取代基为甲基时, 硝化产物为2-(二硝基亚甲基)-5,5-二硝基嘧啶-4,6-二酮(1), 1的水解产物为1,1-二氨基-2,2-硝基乙烯 (FOX-7) 和二硝基甲烷(2). 2-位取代基为羟基时, 硝化产物为5,5-二硝基巴比妥酸(7b), 7b水解可制得偕二硝基乙酰基脲(9b), 9b与KOH作用生成偕二硝基乙酰基脲钾盐(10b)和二硝基甲烷钾盐(11). 2-位取代基为氨基时, 硝化开环生成偕二硝基乙酰基胍(9a), 9a与KOH作用生成偕二硝基乙酰基胍钾盐(10a)和11. 当2-位无取代基时, 硝化产物无法分离, 结构推测为7c. 考察了亲核试剂对FOX-7收率的影响并对FOX-7的三种合成方法进行了评价, 对反应机理进行了探讨.

Synthesis and Reactions of 2-Substituted-1,4,5,6-tetrahydro-5,5- gem-dinitropyrimidine-4,6-diones

Nitration of some 2-substituted-1,4,5,6-tetrahydro-pyrimidine-4,6-diones gave several new 2-substituted-1,4,5,6-tetrahydro-5,5-gem-dinitropyrimidine-4,6-diones (3) in high yields (＞80%). The gem- dinitro products formed were easily attacked by nucleophiles with the formation of gem-dinitroacetyl derivatives, which in turn could be further hydrolyzed to the salts of dinitromethane. When the substituent at position 2 was an alkyl group, the nitration occurred both at position 5 and α-carbon atom of the side chain. If the alkyl group was methyl, the product would be 2-(dinitromethylene)-5,5-dinitropyrimidine-4,6-dione (1), which was hydrolyzed to form 1,1-diamino-2,2-dinitroethylene (FOX-7) and dinitromethane (2). When the substituent was hy-droxyl, the nitrated product was 5,5-dinitrobarbituric acid (7b), which was hydrolyzed to form gem-dinitroacetylurea (9b). 9b reacted with KOH to form potassium gem-dinitroacetylurea (10b) and potassium dinitromethane (11). When the substituent was amino, gem-dinitroacetylguanidine (9a) could be synthesized by hydrolytic cleavage of nitrated product. 9a reacted with KOH to form potassium gem-dinitroacetylguanidine (10a) and 11. When there was no substituent at position 2, 7c with its structure being postulated was obtained. The effect of different nucleophiles on yield of FOX-7 was compared. Three different synthetic routes to FOX-7 were appraised. The reaction mechanism was discussed.