12-Tungstophosphoric acid supported on zirconia as an efficient and heterogeneous catalyst for the synthesis of bis(indolyl)methanes and tris(indolyl)methanes

Silica supported heteropolyacid catalyzed dehydration of aldoximes to nitriles and alcohols to alkenes

“…Supported HPA has proven to be the efficient catalysts for several organic transformations such as C-alkylation (25), esterification (26), Ritter reaction (27), Bigenelli reaction (28), and DakinÁWest reaction (29). Our group has also explored the catalytic activity of HPA for various other transformations (30,31). In continuation of our work on HPA, we herein report an expedient method of silica supported HPA catalyzed liquid phase dehydration of aldoximes to nitriles under mild reaction conditions.…”

An eco-friendly procedure for the efficient synthesis of bis(indolyl)methanes in aqueous media

“…Even when the desired reactions proceed, more than stoichiometric amounts of Lewis acids are required. Many attempts have been done by organic chemists to circumvent this problem [17][18][19][20][21][22]. However, most of the reported methods suffer from one or more of the following drawbacks: using large amounts of solid supports or un-recyclable catalysts which would eventually result in the generation of a large amount of toxic waste, long reaction times, moderate yields of the products, amenable only for aldehydes as carbonyl compounds and requiring an additional microwave or ultrasound irradiation.…”

Iron‐containing ionic liquid as an efficient and recyclable catalyst for the synthesis of C3‐substituted indole derivatives

“…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.…”