Tan Guangying, You Qiulin, Lan Jingbo, You Jingsong
Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry, Sichuan University, 29 Wangjiang Road, Chengdu, 610064, P. R. China.
Angew Chem Int Ed Engl. 2018 May 22;57(21):6309-6313. doi: 10.1002/anie.201802539. Epub 2018 Apr 23.
The functionalization of thiophenes is a fundamental and important reaction. Herein, we disclose iridium-catalyzed one-pot annulation reactions of (benzo)thiophenes with (hetero)aromatic or α,β-unsaturated carboxylic acids, which afford thiophene-fused coumarin-type frameworks. Dearomatization reactions of 2-substituted thiophenes with α,β-unsaturated carboxylic acids deliver various thiophene-containing spirocyclic products. The occurrence of two interconnected reactions provides direct evidence for a Heck-type pathway. The mechanistic scenario described herein is distinctly different from the S Ar and concerted metalation-protodemetalation (CMD) pathways encountered in the well-described oxidative C-H/C-H cross-coupling reactions of thiophenes with other heteroarenes.
噻吩的官能化是一种基本且重要的反应。在此，我们报道了铱催化的（苯并）噻吩与（杂）芳族或α,β-不饱和羧酸的一锅环化反应，该反应可得到噻吩稠合的香豆素型骨架。2-取代噻吩与α,β-不饱和羧酸的去芳构化反应可生成各种含噻吩的螺环产物。这两个相互关联的反应的发生为Heck型反应途径提供了直接证据。本文描述的机理与噻吩与其他杂芳烃的氧化C-H/C-H交叉偶联反应中遇到的S Ar和协同金属化-质子脱金属化（CMD）途径明显不同。
