Rhodaelectro-Catalyzed Synthesis of Pyrano[3,4‑b]indol-1(9H)‑ones via the Double Dehydrogenative Heck Reaction between Indole-2-carboxylic Acids and Alkenes

A rhodaelectro-catalyzed double dehydrogenative Heck reaction of indole-2-carboxylic acids with alkenes has been developed for the synthesis of pyrano­[3,4-b]­indol-1­(9H)-ones. The weakly coordinating carboxyl group is utilized twice as a directing group to activate the C–H bonds throughout the reaction. This reaction precedes an acceptorless dehydrogenation under exogenous oxidant-free conditions in an undivided cell with a constant current.