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本文报告关于应用在第Ⅰ报中的合成途径,合成几种2-取代-5,6(4)-二羟基嘧啶的结果。1.合成所必要的α-苯甲氧基甲酰乙酸乙酯(Ⅳ),以苯甲氧基乙酸乙酯与甲酸乙酯在无水乙醚中在甲醇钠的作用下缩合制得。2.将Ⅳ与脒的各衍生物缩合,得到以下各2-取代-6(4)-羟基-5-苯甲氧基嘧啶:(Ⅴ,R=OH),(Ⅵ,R=NH_2),(Ⅶ,R=CH_3),(Ⅶ,R=SH)和(Ⅸ,R=SC_2H_5)。将Ⅷ或Ⅸ以 Raney 镍进行去硫反应,得到在2-位无取代基的6(4)-羟基-5-苯甲氧基嘧啶(X,R=H)。在以 Raney 镍处理时,苯甲基未遭受氢解,是值得注意的。3.以上5-苯甲氧基嘧啶的去苯甲基反应是顺利的,在 Adams 的氧化亚钯催化剂作用下进行氢解,得到以下的2-取代-5,6(4)-二羟基嘧啶:(Ⅺ,R=OH,即异巴比酸),(Ⅻ,R=NH_2),(ⅩⅢ,R=CH_3)和(ⅩⅣ,R=H)。除了异巴比酸(Ⅺ)和2-胺基-5,6(4)-二羟基嘧啶(Ⅻ)是在过去曾自其他途径制备过者外,以上各化合物都是前所未知者;它们都是高熔点(分解)稳定的晶体。4.由于5-位羟基的芳香性,这些嘧啶与三氯化铁氨溶液,氢氧化钡和磷钼酸均有颜色反应。特别引起注意的是这些嘧啶与前所报告(第Ⅰ报)的各2-取代-4,5,6-三羟基嘧啶和抗坏血酸同样地也能使2,6-Dichlorophenolindophenol 溶液脱色。相应的5-苯甲氧基嘧啶没有这些性质。5.关于这个能使2,6-Dichlorophenolindophenol 溶液脱色的反应所包含的化学变化是以以上嘧啶(2-取代和2-无取代的5,6(4)-二羟基嘧啶和4,5,6-三羟基嘧啶)所共有的烯二醇结构,并参照抗坏血酸的特性作了一些讨论。
This paper reports the results of the synthesis of several 2-substituted-5,6 (4) -dihydroxypyrimidines for the synthetic route used in the first report. 1. Synthesis of ethyl α-benzyloxycarbonyl ethyl acetoacetate (Ⅳ), with ethyl benzyloxyacetate and ethyl formate in anhydrous ethyl ether in the role of sodium methoxide condensation in the system. 2. Condensation of each derivative of IV with an amidine affords the following 2-substituted-6 (4) -hydroxy-5-benzyloxypyrimidines: (V, R = OH) (VII, R = CH_3), (VII, R = SH) and (IX, R = SC_2H_5). Desulphurization of VIII or IX with Raney nickel gives the 6 (4) -hydroxy-5-benzyloxypyrimidine (X, R = H) without substituent at the 2-position. It is noteworthy that the benzyl group is not subjected to hydrogenolysis when treated with Raney nickel. 3. The benzylbenzyl reaction of the above 5-benzyloxypyrimidines was successful and hydrogenolysis was performed under the Adams palladium-oxide catalyst to give the following 2-substituted-5,6 (4) -dihydroxypyrimidines : (Ⅺ, R = OH, ie, barbituric acid), (Ⅻ, R = NH_2), (XIII, R = CH_3) and (XIV, R = H). Each of the above compounds is a hitherto unknown except that isobarbic acid (XI) and 2-amino-5,6 (4) -dihydroxypyrimidine (XII) have been prepared in other ways in the past; Are high melting point (decomposition) stable crystal. 4. Due to the aromatic nature of the hydroxyl at the 5-position, these pyrimidines react with the ferric chloride ferric solution, barium hydroxide and phosphomolybdic acid in color. Of particular note is the ability of these pyrimidines to decolorize the 2,6-Dichlorophenolindophenol solution in the same manner as each of the 2-substituted-4,5,6-trihydroxypyrimidine and ascorbic acid reported previously (Volume I). The corresponding 5-benzyloxypyrimidines do not have these properties. 5. The chemical changes involved in this reaction to decolorize the 2,6-Dichlorophenolindophenol solution are indicated by the above pyrimidine (2-substituted and 2-unsubstituted 5,6 (4) -dihydroxypyrimidine and 4,5,6 - trihydroxypyrimidine) common to the enediol structure, and with reference to the characteristics of ascorbic acid made some discussion.