Relay Visible-Light Photoredox Catalysis: Synthesis of Pyrazole Derivatives via Formal [4 + 1] Annulation and Aromatization

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• 作者：Jian Cheng ; Weipeng Li ; Yingqian Duan ; Yixiang ChengShouyun Yu ; Chengjian Zhu
• 刊名：Organic Letters
• 出版年：2017
• 出版时间：January 6, 2017
• 年：2017
• 卷：19
• 期：1
• 页码：214-217
• 全文大小：446K
• ISSN：1523-7052

文摘

A relay visible-light photoredox catalysis strategy has been accomplished. Three successive photoredox cycles (one oxidative quenching cycle and two reductive quenching cycles) are engaged in a single reaction with one photocatalyst. This strategy enables formal [4 + 1] annulation of hydrazones with 2-bromo-1,3-dicarbonyl compounds, which functionalizes three C–H bonds of hydrazones. This method affords rapid access to a complex and biologically important pyrazole scaffold in a step-economical manner with high efficiency under mild conditions.