Silica Gel Supported Sodium Hydrogen Sulfate as an Efficient and Reusable Heterogeneous Catalyst for the Synthesis of Imines in Solvent‐Free Conditions under Microwave Irradiation.

Abstract

Microwave Irradiation. -A variety of imines (37 examples in all) is prepared in high yields by a microwave-assisted procedure using NaHSO4·SiO2 as an efficient heterogeneous catalyst. -(GOPALAKRISHNAN*, M.; SURESHKUMAR, P.; KANAGARAJAN, V.; THANUSU, J.; GOVINDARAJU, R.; J.

Activated fly ash-catalyzed synthesis of naphthyl-substituted cyclohexenone carboxylates, indazolonols, and nitro hydrazones in “dry media”

“…In the HOMOCOR spectrum of 17, the signal at 4.22Á4. 24 . The observed ÁNH, C0N, C0C, and NO 2 stretching vibrational bands are supporting evidence for the formation of synthesized compound 25.…”

“…Activated fly ash was used to catalyze a variety of organic reactions including Knoevenagel condensation; ''one-pot'' conversions of ketones to amides via Beckmann rearrangement, Schiff bases formation, and Biginelli and Hantzsch reactions (24); ''onepot'' synthesis of 1,2,4,5-tetrazinanes (25); microwave-assisted, solvent-free alkylation and acylation of 2-mercaptobenzothiazole (26); different ether and ester derivatives of carvacrol (27); liquid-phase esterification of salicylic acid (28) with acetic anhydride and methanol; grindstone chemistry solid-state reaction procedure for the synthesis of heterocyclic oximes (29); and one-pot synthesis of pyrimidino thiazolidin-4-ones (30). Moreover, in several adsorption processes, fly ash was used as a cost-effective adsorbent for removal of pollutants in air and water systems (31,32).…”

“…Two major constituents of fly ash Á namely, silica and alumina Á drive the reaction to proceed smoothly (24). Later this addition product undergoes an intramolecular aldol reaction in the presence of activated fly ash, which serves as a dehydrating agent to furnish ethyl 4-(naphthalen-2-yl)-2-oxo-6-arylcyclohex-3-ene- condensation reaction, with two molecules joining together with loss of water.…”

Three component one-pot synthesis of novel pyrimidino thiazolidin-4-ones catalyzed by activated fly ash

“…The catalyst and other solid wastes were removed by filtration. The combined organic layer was washed with 10% sodium bicarbonate solution followed by water three times and then dried over anhydrous MgSO 4 . The organic layer was concentrated in vacuo to furnish the products, which were purified by column chromatography using silica gel (100Á200 mesh), with ethyl acetate Á petroleum ether (bp 40Á 60) in the ratio (2:8) Green Chemistry Letters and Reviews 165…”

“…Many researchers devoted themselves to the research of the potential activity of fly ash and the hydration process of fly ash cement (3). Recently, microwave-assisted synthesis of ''one-pot'' conversion of ketones into amides, Knoevenagel condensation, Schiff bases formation, Biginelli and Hantzsch reactions were carried out using activated fly ash as catalyst (4). In addition, activated fly ash is used for the ''one-pot'' synthesis of 1,2,4,5-tetrazines (5) and 1,2,3-selenadiazoles (6).…”