Microwave‐Assisted Rhodium (III)‐Catalyzed [3+3] Annulation of 2‐Benzyl‐2H‐Indazole‐6‐carboxylic Acids with Iodonium Ylides: A Regioselective Synthesis of Indazole‐Fused Chromenes

Abstract

A Rh (III)‐catalyzed redox‐neutral C‐H activation/ [3+3] cyclization of 2‐benzyl‐2H‐indazole‐6‐carboxylic acids with iodonium ylides under microwave irradiation for the synthesis of indazole‐fused chromenes has been reported. The critical feature of this method is that the C‐H activation of the C7‐H bond of 2‐benzyl‐2H‐indazole‐6‐carboxylic acid proceeds with regioselectivity in the presence of the proximate C5‐H bond without the need for external oxidant. Microwave irradiation reduced the reaction time as compared to conventional heating. The detailed mechanistic study disclosed the mechanistic pathway of the reaction.