Regioselectivity of the thermal van Alphen–Hüttel rearrangement of 4- and 5-mono- and 4,5-disubstituted 3,3-diphenyl-3H-pyrazoles

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• 作者：V. A. Vasin ; V. V. Razin ; E. V. Bezrukova…
• 刊名：Russian Journal of Organic Chemistry
• 出版年：2016
• 出版时间：June 2016
• 年：2016
• 卷：52
• 期：6
• 页码：862-872
• 全文大小：341 KB
• 刊物主题：Organic Chemistry;
• 出版者：Springer US
• ISSN：1608-3393
• 卷排序：52

文摘

Thermal van Alphen–Hüttel rearrangement of methyl 3,3-diphenyl-3H-pyrazole-4-carboxylate, 3,3-diphenyl-3H-pyrazole-4-carbonitrile, and methyl 5-methyl-3,3-diphenyl-3H-pyrazole-4-carboxylate involves completely regioselective migration of one phenyl group from the 3-position to N2 with formation of aromatic 1H-pyrazole system. Thermal rearrangement of methyl 3,3-diphenyl-3H-pyrazole-5-carboxylate leads to the formation of methyl 4,5-diphenyl-1H-pyrazole-3-carboxylate as a result of migration of the 3-phenyl group exclusively to the C4 atom and subsequent prototropic isomerization. Under analogous conditions, methyl 4-methyl-3,3-diphenyl-3H-pyrazole-5-carboxylate, methyl 5-(methanesulfonyl)-3,3-diphenyl-3H-pyrazole-4-carboxylate, methyl 5-(benzenesulfonyl)-3,3-diphenyl-3H-pyrazole-4-carboxylate, and dimethyl 3,3-diphenyl-3H-pyrazole-4,5-dicarboxylate have been regioselectively converted into the corresponding 4H-pyrazoles. Thermolysis of 5-(4-methylbenzenesulfonyl)-3,3-diphenyl-3H-pyrazole-4-carbonitrile gives rise to a mixture of 1H- and 4H-pyrazoles, the former considerably prevailing, whereas the corresponding 1H-pyrazoles are formed as the only product from 5-(methanesulfonyl)- and 5-(benzenesulfonyl)-3,3-diphenyl-3H-pyrazole-4-carbonitriles.Original Russian Text © V.A. Vasin, V.V. Razin, E.V. Bezrukova, P.S. Petrov, 2016, published in Zhurnal Organicheskoi Khimii, 2016, Vol. 52, No. 6, pp. 876–886.