Hydrogen-Bond-Catalyzed Arylationof 3-(Aminoalkyl)indoles via C-N Bond Cleavage with Thiourea under Microwave Irradiation: An Approach to 3-(α,α-Diarylmethyl) indoles

We have developed a simple and efficient method for the arylation of 3-(aminoalkyl) indoles with aryl alcohols and other aromatic nucleophiles through C-N bond cleavage under microwave irradiation to synthesize 3-(alpha, alpha-diarylmethyl) indoles. The method uses thiourea as catalyst, which is environmentally benign, water-tolerant and easy to handle. Notably, acid-sensitive substrates are tolerated under the reaction conditions. Thiourea activates the tertiary amine through double hydrogen bonding and converts it into a better leaving group. The reaction proceeds through the formation of vinylogous iminium ion as an intermediate.