“…Therefore, various methods have been reported for preparing this class of compounds . The most straightforward method to obtain the heterocycle involves the condensation of indoles with different carbonyl compounds (aldehydes or ketones), which was often promoted by homo‐ and heterogeneous catalysts such as acid catalysts, nano catalysts, supported catalysts, metal catalysts, ion exchange resin, and enzymes . Although these reported protocols have made some certain merits, many of them still have notable disadvantages such as harsh reaction conditions, long reaction times, limited substrate scope, using expensive Lewis acids and solvents, high catalyst loading and generation of large amounts of harmful wastes.…”