A mild and regioselective Ullmann reaction of indazoles with aryliodides in water

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• 作者：Xiao Ding^a ; ¹ ; Jingtao Bai^b ; ¹ ; Hailong Wang^a ; Baowei Zhao^a ; Jian Li^b ; Feng Ren^a ; ^{feng.q.ren@gsk.com}
• 关键词：1-Aryl-1H-indazoles ; Ullmann reaction ; Aqueous micelles ; Tween 20 ; Regioselective
• 刊名：Tetrahedron
• 出版年：2017
• 出版时间：12 January 2017
• 年：2017
• 卷：73
• 期：2
• 页码：172-178
• 全文大小：1018 K
• 卷排序：73

文摘

A mild and regioselective Ullmann reaction of indazoles with aryliodides has been developed as a general method for the synthesis of 1-aryl-1H-indazoles. Water was used as the solvent wherein Tween 20 (2% w/w) was added to form aqueous micelles to improve solubility of starting materials and accelerate reaction rate. This aqueous protocol allows the Ullmann reaction to proceed at a mild temperature (60 °C) within a short reaction time (2 h), which typically requires high temperatures (≥100 °C) and prolonged duration (≥24 h). The protocol demonstrated broad substrate scopes with good isolated yields and high regioselectivity (N-1 arylation over N-2 arylation) for 25 examples examined.