Chiral squaramide catalyzed synthesis of C4 substituted chiral pyrazol-3-ol derivatives via a facile asymmetric Michael addition of 3-methyl-2-pyrazolin-5-one to β-nitrostyrenes

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• 作者：Kadiyala Srinivasa Rao^a ; Pambala Ramesh^a ; Rajiv Trivedi^a ; ; M. Lakshmi Kantam^a ; ^b ; ^c
• 关键词：Squaramide ; Michael addition ; Pyrazolones ; Bifunctional catalysts ; Enantioselectivity
• 刊名：Tetrahedron Letters
• 出版年：2016
• 出版时间：16 March 2016
• 年：2016
• 卷：57
• 期：11
• 页码：1227-1231
• 全文大小：639 K

文摘

Asymmetric Michael addition of 3-methyl-2-pyrazolin-5-one to β-nitrostyrenes, catalyzed by a series of chiral squaramide bifunctional catalysts derived from cinchona alkaloids, yielded chiral pyrazol-3-ol derivatives. These pyrazol-3-ol derivatives were obtained in moderate to high yields with good enantioselectivities under mild conditions using 1 mol % of the catalyst. This reaction affords valuable and easy access to chiral 5-methyl-4-(2-nitro-1-arylethyl)pyrazol-3-ol derivatives.