Tandem [2 + 2] Cycloaddition/Rearrangement toward Carbazoles by Visible-Light Photocatalysis.

Reported herein is the first example of the synthesis of carbazoles via oxidative cyclization of 3-alkenylindoles with styrenes under visible light. The irradiation of a catalytic amount of [Ir(dtbbpy)(ppy)2][PF6] as the photocatalyst enables various 3-alkenylindoles and styrenes to undergo tandem [2 + 2] cycloaddition/rearrangement, thereby leading to carbazole derivatives in good to excellent yields under aerobic conditions. Mechanistic studies reveal that photoinduced energy transfer followed by electron transfer is responsible for the tandem reaction.

A sustainable synthesis of 2-aryl-3-carboxylate indolines from N-aryl enamines under visible light irradiation.

With visible light irradiation of a catalytic amount of Ir(ppy)3 at room temperature, a number of N-aryl enamines were transformed into their corresponding indoline products in good to excellent yields without requiring any extra additives. This is the first example of the synthesis of indolines via the intramolecular cyclization of enamines under visible light irradiation.