Cobalt(III)-Catalyzed [5 + 1] Annulation for 2H-Chromenes Synthesis via Vinylic C–H Activation and Intramolecular Nucleophilic Addition

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• 作者：Ramajayam Kuppusamy ; Krishnamoorthy Muralirajan ; Chien-Hong Cheng
• 刊名：ACS Catalysis
• 出版年：2016
• 出版时间：June 3, 2016
• 年：2016
• 卷：6
• 期：6
• 页码：3909-3913
• 全文大小：445K
• 年卷期：0
• ISSN：2155-5435

文摘

A new cobalt-catalyzed phenolic OH-assisted C–H functionalization of 2-vinylphenols with allenes to give various 2H-chromenes is described. It is the first time that allenes are used as the coupling partners in the cobalt-catalyzed C–H activation reactions. In most cases, cobalt-catalyzed oxidative annulation of arenes with alkenes or alkynes via C–H activation gave [4 + 2] or [3 + 2] cyclization products, but the present catalytic reaction afforded an oxidative [5 + 1] cyclization products with the allenes acting as a one-carbon coupling partner. The catalytic reaction is proposed to proceed via the C–H activation of the vinyl group, allene insertion, and an unusual intramolecular regioselective phenoxide addition.