Silica supported lanthanum trifluoroacetate and trichloroacetate as an efficient and reusable water compatible Lewis acid catalyst for synthesis of 2,4,5-triarylimidazoles via a solvent-free green approach

Abstract

Silica supported lanthanum trifluoroacetate and trichloroacetate as green Lewis acid catalysts were developed by a novel, simple, cheap, and environment friendly method and utilized them in the synthesis of arylimidazole derivatives via one pot solvent-free approach.

Water compatible silica supported iron trifluoroacetate and trichloroacetate: as prominent and recyclable Lewis acid catalysts for solvent-free green synthesis of hexahydroquinoline-3-carboxamides

“…This variation in the crystallinity of silica-supported Lewis acid is due to the strong electrostatic interaction between iron trifluoroacetate/trichloroacetate and mesoporous silica, which further transforms the supported Lewis acids into an amorphous nature. 14,49 This result provides strong confirmation about the fine dispersion of iron trifluoroacetate and trichloroacetate over mesoporous silica material in the present silica-supported Lewis acids, [Fe(OCOCF 3 ) 3 · n H 2 O/SiO 2 ] and [Fe(OCOCCl 3 ) 3 · n H 2 O/SiO 2 ].…”

“…While third TG curve at the temperature range of 247 °C to 370 °C was corresponding to the complete loss of trifluoroacetate and trichloroacetate groups leading to the formation of FeF 3 and FeCl 3 as the decomposition product with a high weight loss of 76% and 90% respectively. 14,44,45 However, the second characteristic TG curve for silica supported iron trifluoroacetate and trichloroacetate catalysts, caused due to the partial loss of trifluoroacetate and trichloroacetate groups are obtained at the temperature range of 210 °C to 308 °C with minimum weight loss of 17 and 20%, respectively. Further, the third TG curve was observed at the temperature range of 367 °C to 428 °C, corresponding to the complete loss of trifluoroacetate and trichloroacetate groups with maximum weight loss of 21 and 23% respectively.…”

“…Moreover, it is widely known that the iron trifluoroacetate and trichloroacetate catalysts supported by silica primarily include Lewis acidity, which actually originated from the loaded iron trifluoroacetate or trichloroacetate. 14,72…”

“…The iron trifluoroacetate and iron trichloroacetate were prepared via new and novel method 14 by the direct reaction between iron( iii ) acetate (2 g) and an excess quantity of trifluoroacetic acid/trichloroacetic acid (9 g) respectively in 1 : 3 equivalent ratio. The reaction mixture was heated at 60 °C for 6–8 hours.…”

“…These catalysts include lanthanide triates, rare earth metal triates, transition metal triates, triuoroacetic acid or trichloroacetic acid, iron tri-uoromethanesulfonate, iron triuoroacetate, lanthanum tri-uoroacetate and lanthanum trichloroacetate. [14][15][16][17][18][19] Additionally, many mesoporous nano organosilica materials were utilized in different organic transformations which includes Pdcontaining IL-based ordered nanostructured organosilica, 20 a Pd-containing magnetic periodic mesoporous organosilica nanocomposite, 21 a Cu-containing magnetic yolk-shell structured ionic liquid based organosilica nanocomposite, 22 highly ordered mesoporous organosilica-titania with an ionic liquid framework, 23 copper/IL-containing magnetic nanoporous MCM-41, 24 core-shell structured Fe 3 O 4 @SiO 2 -supported IL/ [Mo 6 O 19 ], 25 an ionic liquid/Mn complex immobilized on phenylene based periodic mesoporous organosilica, 26 phenylene and isatin based bifunctional mesoporous organosilica supported Schiff-base/manganese complexes, 27 aminefunctionalized ionic liquid-based mesoporous organosilica, 28 magnetic ethylene-based periodic mesoporous organosilica supported palladium, 29 phenylene-based periodic mesoporous organosilica supported melamine, 30 a magnetic silica nanocomposite supported W 6 O 19 /amine, 31 phenyl and ionic liquid based bifunctional periodic mesoporous organosilica supported copper, 32 magnetic silica supported propylamine/ H 3 PW 12 O 40 . 33 The green Lewis acids are highly efficient chemo, regio and stereoselective catalysts for widespread series of organic reactions including Diels-Alder reaction, aldol condensation, Friedel-Cras alkylation, and acylation reaction, Baylis-Hillman reaction, radical addition, Michael reactions, Mannich reaction, alkene alkylation and dimerization, heterocyclic molecule synthesis, Reformatsky reaction, aromatic nitration, sulphonation and bromination reactions, rearrangement reactions, and many multicomponent, cyclization and ring-opening reactions.…”