N-Heterocyclic Carbene Catalyzed [4 + 2] Annulation Reactions with in Situ Generated Heterocyclic ortho-Quinodimethanes

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• 作者：Jianfeng Xu ; Shiru Yuan ; Maozhong Miao
• 刊名：Organic Letters
• 出版年：2016
• 出版时间：August 5, 2016
• 年：2016
• 卷：18
• 期：15
• 页码：3822-3825
• 全文大小：425K
• 年卷期：0
• ISSN：1523-7052

文摘

An efficient strategy for the in situ generation of heterocyclic ortho-quinodimethanes (oQDMs) from 2-methyl-heteroarene-3-carboxylic esters by N-heterocyclic carbene (NHC) catalysis is disclosed. These heterocyclic oQDMs undergo highly enantioselective [4 + 2] annulation reactions with isatin-derived ketimines to afford optically pure heteroarene-fused δ-lactams bearing a quaternary stereogenic center. The main features of this reaction include challenging direct C(sp³)–H bond functionalizations, excellent enantioselectivities, readily available starting materials, mild reaction conditions, high efficiency, and operational simplicity.