Combined Gold and Photoredox Catalysis: Synthesis of 3‐Alkenyl‐2H‐Indazoles from 2‐Alkynylazobenzenes

Abstract

We disclose the intramolecular synthesis of 3‐alkenyl‐2<i>H</i>‐indazoles from 2‐alkynylazobenzenes promoted by a dual catalysis using AuCl3 and a ruthenium photocatalyst under irradiation with visible light. This reaction goes through a hydroamination of the alkynyl fragment. The yields are governed by the electronic factors. Control experiments and DFT calculations suggest that a radical and polar mechanisms are operating in parallel. This transformation goes through first formation and C‐N bond and 1,2‐hydride shift. Derivatization was also carried out to extend the versatility of this methodology.