Investigations of the Richter reaction in a series of vicinal alkynylpyrazolediazonium salts
作者:Eugene V. Tretyakov、David W. Knight、Sergei F. Vasilevsky
DOI:10.1039/a903755a
日期:——
All positional isomers of vic-alkynylaminopyrazoles, when treated with sodium nitrite in hydrochloric or hydrobromic acid, are transformed into pyrazolopyridazines via cyclisation of the corresponding alkynylpyrazolyldiazonium salts. The ease of cyclisation was found to depend markedly on the position of the alkynyl and diazonium groups around the pyrazole nucleus: 4-alkynylpyrazole-5-diazonium salts derived from the corresponding 4-alkynyl-5-aminopyrazoles 1a–c cyclized at 0–20 °C to 4-chloro- and 4-bromo-1H-pyrazolo[3,4-c]pyridazines 2a–c and 3a; the heterocyclization of 5-alkynylpyrazole-4-diazonium salts 5a,b required heating to 100–105 °C and gave 7-chloro-1H-pyrazolo[4,3-c]pyridazines 6a,b in good yield. The cyclisation of 1-methyl-3-alkynylpyrazole-4-diazonium salts 8a,b was accompanied by methyl group migration towards the neighbouring nitrogen atom to give the same 7-chloro-1H-pyrazolo[4,3-c]pyridazines 6a,b arising from cyclisation of the 5-alkynylpyrazole-4-diazonium salts 5a,b. When treated with sodium hydrogen carbonate, the 1,5-dimethylpyrazol-4-diazonium salts 8a–c gave the 5-(pyrazol-4-ylazomethyl)pyrazole-4-diazonium chloride derivatives 9a–c which cyclized in the presence of base to give the corresponding 6-(pyrazol-4-ylazo)-4H-pyrazolo[4,3-c]pyrazoles 10a–c.In contrast, the heterocyclization of 4-alkynylpyrazole-3-diazonium salts derived from 4-alkynyl-3-aminopyrazoles 11a,b at 50–60 °C gave 4-hydroxy-2H-pyrazolo[3,4-c]pyridazines 12a,b as the major components together with the corresponding 6-halogeno-pyridazines 13a,b and 14a as minor components.
用亚硝酸钠在盐酸或氢溴酸中处理沧炔基氨基吡唑时,通过相应的炔基吡唑重氮盐的环化作用,沧炔基氨基吡唑的所有位置异构体都会转化为吡唑并哒嗪。环化的难易程度明显取决于吡唑核周围炔基和重氮基的位置:由相应的 4-炔基-5-氨基吡唑 1a-c 生成的 4-炔基吡唑-5-重氮盐在 0-20 °C 下环化生成 4-氯和 4-溴-1H-吡唑并[3,4-c]哒嗪 2a-c 和 3a;5-炔基吡唑-4-重氮盐 5a,b 的杂环化反应需要加热至 100-105 ℃,得到 7-氯-1H-吡唑并[4,3-c]哒嗪 6a,b,收率很高。在 1-甲基-3-炔基吡唑-4-重氮盐 8a,b 的环化过程中,甲基向邻近的氮原子迁移,从而得到了与 5-炔基吡唑-4-重氮盐 5a,b 环化过程相同的 7-氯-1H-吡唑并[4,3-c]哒嗪 6a,b。用碳酸氢钠处理后,1,5-二甲基吡唑-4-重氮盐 8a-c 生成 5-(吡唑-4-基氮甲基)吡唑-4-重氮氯化物衍生物 9a-c,这些衍生物在碱存在下发生环化,生成相应的 6-(吡唑-4-基氮)-4H-吡唑并[4,3-c]吡唑 10a-c。与此相反,在 50-60 °C 的温度下,由 4-炔基-3-氨基吡唑 11a,b 衍生出的 4-炔基吡唑-3-重氮盐进行杂环化反应,得到 4-羟基-2H-吡唑并[3,4-c]哒嗪 12a,b(主要成分)以及相应的 6-卤代哒嗪 13a,b 和 14a(次要成分)。