Selective Organocatalytic Synthesis of 3-Methylindoles and Diindolylmethanes through Reductive Methylation of Indoles with CO2.

The direct reductive methylation of indoles with CO2 remains a formidable challenge due to competing reduction pathways and precise selectivity control. Herein, cooperative catalytic systems comprising 2-aminopyridine-BH3 and DIC-BH3 are disclosed, which enable unprecedented chemoselective C3-methylation of indoles under mild conditions (1 atm CO2). This strategy delivers two distinct product classes through controlled reduction: 3-methylindoles (up to 81% yield) and diindolylmethanes (up to 82% yield) with excellent functional group tolerance. This protocol offers novel synthetic routes for the synthesis of indole-based bioactive molecules.