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‐2 H ‐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‐2 H ‐indazole‐6‐carboxylic acid proceeds regioselectively in the presence of the proximate C5−H bond without the need of external oxidant. Microwave irradiation reduced the reaction time as compared to conventional heating. The detailed mechanistic study disclosed the mechanistic pathway of the reaction.