Convenient two step procedures for the synthesis of 2,2′-biimidazole (3)and its dihydrochloride salt (4) starting with bis-methylimidate (1) in an overall yield of 72 and 83%, respectively, are reported. Bis-methylimidate(1) was treated with two equivalents of aminoacetaldehyde dimethyl acetal underacid-catalyzed conditions to provide bis-N-(2,2-dimethoxyethylacetamidine)dihydrochioride (2) in 84% yield. Fusion of 2 with an equivalent of p toluenesulfonic acid at 200°C gave 3 in 86% yield. Alternatively, 2 was refluxed with 5 molar hydrochloric acid to provide 4 as well as 3 in combined yield of 99%. Evidence is presented for the intermediacy of 2-[4(5)-methoxy-2-imidazolyl]imidazole (5) in the formation of the title compound. Water-soluble 4 is converted to 3 by treatment with potassium carbonate.
报道了一种便捷的两步合成2,2′-
双咪唑(3)及其二盐酸盐(4)的方法,起始原料为双甲基
咪唑(1),总体收益分别为72%和83%。将双甲基
咪唑(1)与双等量的
氨基乙醛二甲基缩醛在酸催化条件下反应,得到双-N-(2,2-二甲氧基乙基乙酰胺)二盐酸盐(2),收益为84%。将2与等量的
对甲苯磺酸在200°C下熔融反应,得到3,收益为86%。或者,将2与5摩尔的
盐酸回流反应,得到4以及3,合成收益为99%。提供了中间体2-[4(5)-甲氧基-2-
咪唑基]
咪唑(5)在目标化合物形成过程中的证据。
水溶性的4经过
碳酸钾处理可转化为3。