Magnetically separable sulfonic acid catalysed one-pot synthesis of diverse indole derivatives

Synthesis of Bis(indolyl)methanes Using Hyper-Cross-Linked Polyaromatic Spheres Decorated with Bromomethyl Groups as Efficient and Recyclable Catalysts

“…Direct use of NaOH achieved an 85% yield in 2 h. 40 Kothandapani and co-worker reported magnetically separable sulfonic acid (Fe 3 O 4 –OSO 3 H)-catalyzed one-pot synthesis of BIMs. 41 Even though multistep synthesis of the catalyst was involved, this catalyst gave stoichiometric yields of diverse BIMs. Compared to the reported catalysts, the synthesis of PPy@CH 2 Br is straightforward, the catalyst gives high yield (96%) in 1 h and is recyclable (vide infra), and laborious workup procedures are not needed.…”

Nano-Magnetic Sulfonic Acid Catalyzed Facile Synthesis of Diverse Amide Derivatives

“…To understand the relatively high catalytic potential of Fe 3 O 4 -OSO 3 H over SiO 2 -OSO 3 H, the sulfonic acid loading on the surface was calculated. 21 It was found that Fe 3 O 4 -OSO 3 H had a sulfonic acid group loading of 0.70 mmol g -1 whilst SiO 2 -OSO 3 H had a loading of 0.53 mmol g -1 . We presume that the nano Fe 3 O 4 provided a higher surface area than bulk SiO 2 for sulfonic acid functionalization.…”

“…20 We have recently reported facile and green Fe 3 O 4 -OSO 3 H-catalyzed C-C and C-N bond-forming reactions. 21 Herein, we report the synthesis of symmetrically/unsymmetrically substituted ureas and fatty acid amide derivatives catalyzed by Fe 3 O 4 -OSO 3 H under green, solvent-free reaction conditions.…”

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.…”

“…[8] Therefore, various methods have been reported for preparing this class of compounds. [9][10][11] 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, [12][13][14][15][16][17][18][19][20][21][22][23][24] nano catalysts, [25][26][27][28][29][30][31] supported catalysts, [32][33][34][35][36][37][38][39][40][41] metal catalysts, [42][43][44][45][46][47][48][49] ion *These authors contributed equally to this work. exchange resin, [50] and enzymes.…”