AlCl3·6H2O-Catalyzed Friedel-Crafts Alkylation of Indoles by the para-Quinone Methide Moiety of Celastrol

A classical Friedel-Crafts alkylation of different indoles catalyzed by AlCl3·6H2O has been developed for a well-known important natural product, celastrol, resulting in a series of derivatives for further biological evaluation. The catalyst loading was reduced to 5 mol %, the reaction proceeds at ambient temperature and reaction time is only 3 h. The product yields range from 20% to 99%. A reaction mechanism is also proposed, based on our experiment results