Rhodium(III)-Catalyzed Indole Synthesis Using N-N Bond as an Internal Oxidant
Rhodium(III)-Catalyzed Indole Synthesis Using N-N Bond as an Internal Oxidant
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N-N 键作为内氧化剂的铑 (III) 催化吲哚合成
DOI：
10.1021/ja408541c
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发表时间：
2013-11-06
影响因子：
15
通讯作者：
Zhu, Jin
中科院分区：
文献类型：
--
作者：
Liu, Baoqing;Song, Chao;Zhu, Jin
本文报道了Rh（III）催化的N-亚硝基苯胺与炔的环化反应合成吲哚类化合物。合成方案的特点是一个独特的内部氧化剂，N-N键，作为催化剂周转的反应手柄，以及迄今为止诱人难以捉摸的分子间氧化还原中性歧管，预测后C-H活化，形成一个五元氮杂环。表面上二元的酸性和碱性条件的相容性确保了反应在各种合成环境中的通用性。一系列辅助官能团的耐受性潜在地允许预定义的、可编程的取代模式被并入吲哚支架中。在酸性条件下，全面的机理研究支持[RhCp*]（2+）通常作为催化剂的静止状态（在某些情况下可切换为[RhCp*（（OOCBu）-Bu-t）]（+））和C-H活化作为转换限制步骤。鉴于亚硝基有多种共价键，这种不稳定的官能团很可能被用作各种偶联反应的通用手柄。
We report herein a Rh(III)-catalyzed cyclization of N-nitrosoanilines with alkynes for streamlined synthesis of indoles. The synthetic protocol features a distinct internal oxidant, N-N bond, as a reactive handle for catalyst turnover, as well as a hitherto tantalizingly elusive intermolecular redox-neutral manifold, predicated upon C-H activation, for the formation of a five-membered azaheterocycle. The compatibility of seemingly dichotomous acidic and basic conditions ensures reaction versatility for multifarious synthetic contexts. The tolerance of an array of auxiliary functional groups potentially permits predefined, programmable substitution patterns to be incorporated into the indole scaffold. Comprehensive mechanistic studies, under acidic condition, support [RhCp*](2+) as generally the catalyst resting state (switchable to [RhCp*((OOCBu)-Bu-t)](+) under certain circumstance) and C-H activation as the turnover-limiting step. Given the variety of covalent linkages available for the nitroso group, this labile functionality is likely to be harnessed as a generic handle for strikingly diverse coupling reactions.