Substrate-Controlled Transformation of Azobenzenes to Indazoles and Indoles via Rh(III)-Catalysis

Rh­(III)-catalyzed substrate-controlled
transformation of azobenzenes to indazoles and 2-acyl (NH) indoles
is achieved via C–H functionalization. Generally, good functional
groups tolerance, satisfying yields, and excellent regio-selectivity
are achieved in this reaction. Mechanistically, the reaction with
acrylates undergoes β-hydride elimination, while the reaction
with vinyl ketones or acrylamides undergoes nucleophilic addition.
Copper acetate was supposed to play different roles in the β-hydride
elimination to furnish indazoles and nucleophilic addition of C–Rh
bond to deliver 2-acyl (NH) indoles.

本研究实现了铑(III)催化、底物调控的偶氮苯向吲唑与2-酰基(NH)吲哚的转化反应，该转化通过碳氢键官能团化策略完成。该反应普遍展现出良好的官能团耐受性、优异的反应收率以及出色的区域选择性。从机理层面来看，与丙烯酸酯参与的反应经历β-氢消除路径，而与乙烯基酮或丙烯酰胺参与的反应则遵循亲核加成路径。研究表明，乙酸铜在生成吲唑的β-氢消除过程与生成2-酰基(NH)吲哚的碳-铑键亲核加成过程中发挥了不同的作用。