Microwave-assisted solvent-free synthesis of 14-aryl/alkyl-14H-dibenzo[a,j]xanthenes and tetrahydrobenzo[a]xanthen-11-ones catalyzed by nano silica phosphoric acid

Silica supported Brönsted acids as catalyst in organic transformations: A comprehensive review

“…Bamoniri et al [35] synthesized 1,2,4,5-tetrasubstituted imidazoles using Benzil (4 mmol), amine (4 mmol), aldehyde (4 mmol), ammonium acetate (4 mmol) and nano-SPA (0.08 g) as catalyst. The earlier reported method for its synthesis were by using different catalyst like Zeolite HY, silica gel/NaHSO4, molecular iodine, K5CoW12O40•3H2O, heteropolyacids, HClO4-SiO2, InCl3•3H2O, ZrCl4 and BF3•SiO2 but these suffer from disadvantages like harsh reaction conditions, poor yields, prolonged time period, use of hazardous and often expensive acid catalysts (Scheme 26).…”

“…The catalyst has been used in different chemical reactions like the synthesis of amidoalkyl naphthols [29] and a number of other one component and multicomponent reactions. Based on the excellent results of these reactions, nano-silica phosphoric acid has also been utilized and the results obtained were quite good [35].…”

Boron sulfonic acid (BSA) catalyzed selective synthesis of aryl-bis(2-hydroxynaphth-1-yl)methanes and 14-alkyl- and 14-aryl-14H-dibenzoxanthenes under solvent-free condition

“…It is well established that the combination of microwave energy with solvent-free medium reduces the reaction time and thus make the reaction path cleaner by single product formation. 25 By considering the multifaceted advantages of microwave assisted organic synthesis we decided to investigate the BSA catalyzed reaction of 2-naphthol and aldehydes under microwave irradiation and compare the results with thermal energy to identify the exact conditions for selective synthesis of 3 and 4.…”

Camphor-10-sulfonic acid catalyzed condensation of 2-naphthol with aromatic/aliphatic aldehydes to 14-aryl/alkyl-14H-dibenzo[a,j]xanthenes

“…Several methods have been reported for the synthesis of xanthenes and benzoxanthenes, which include trapping of benzynes with phenols, 8 cyclodehydration, 9 cyclocondensation of 2-hydroxyaromatic aldehydes with 2-tetralone 10 and intramolecular phenyl carbonyl coupling reactions of benzaldehydes 1052 KUNDU and NAYAK and acetophenones. 14 Moreover, various catalysts, including TaCl 5 , 15 Sr(OTf) 2 , 16 Yb(OTf) 3 , 17 sulfamic acid, 18 iodine, 19 Amberlyst-15, 20 cyanuric chloride, 21 ceric ammonium nitrate (CAN), 22 27 an ionic liquid, 28 dodecylphosphonic acid (DPA) or dodecylsulfamic acid (DSA), 29 nano-silica phosphoric acid (nano-SPA), 30 nano-SnCl 4 ·SiO 2 , 31 4-dodecylbenzenesulfonic acid (DBSA), 32 tungstophosphoric acid 33 and a functionalized mesoporous material 34 were found to catalyze condensation reactions of 2-naphthol with different aldehydes to afford 14-substituted-14H-dibenzo[a,j]xanthenes. 14 Moreover, various catalysts, including TaCl 5 , 15 Sr(OTf) 2 , 16 Yb(OTf) 3 , 17 sulfamic acid, 18 iodine, 19 Amberlyst-15, 20 cyanuric chloride, 21 ceric ammonium nitrate (CAN), 22 27 an ionic liquid, 28 dodecylphosphonic acid (DPA) or dodecylsulfamic acid (DSA), 29 nano-silica phosphoric acid (nano-SPA), 30 nano-SnCl 4 ·SiO 2 , 31 4-dodecylbenzenesulfonic acid (DBSA), 32 tungstophosphoric acid 33 and a functionalized mesoporous material 34 were found to catalyze condensation reactions of 2-naphthol with different aldehydes to afford 14-substituted-14H-dibenzo[a,j]xanthenes.…”