Poly(4-vinylpyridine)-supported dual acidic ionic liquid: an environmentally friendly heterogeneous catalyst for the one-pot synthesis of 4,4'-(arylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ols)

Abstract

Abstract:A poly(4-vinylpyridine)-supported Brønsted ionic liquid was easily prepared from its starting materials and used as a novel, highly efficient, and reusable heterogeneous catalytic system for the synthesis of 4,4'-(arylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ols) from the condensation reaction between aromatic aldehydes and 2 equivalents of 3-methyl-l-phenyl-5-pyrazolone.

Carbon Nanotube-Supported Butyl 1-Sulfonic Acid Groups as a Novel and Environmentally Compatible Catalyst for the Synthesis of 1,8-Dioxo-octahydroxanthenes

“…As can be seen in the spectrum of MWCNT-BuSO 3 H new peaks appeared at 1120, 1150, 1190, and 1230 cm -1 , which can be assigned to S=O stretching vibration. 25,26 The thermogravimetric analyses (TGA) of MWCNTs, before and after the functionalization processes, are provided in Figure 2. The TGA curves of MWCNT-OH and MWCNT-BuSO 3 H displayed a weight loss around 100 o C which is corresponding to the loss of the physically adsorbed water.…”

“…In a continuation of our recent work on synthesis and application of heterogeneous catalysts in organic reactions, [25][26][27][28] herein we now report the synthesis of multiwalled carbon nanotube-supported butyl 1-sulfonic acid groups (MWCNT-BuSO 3 H) from the reaction of the salt form hydroxyl functionalized multiwalled carbon nanotube (MWCNT-OH) with 1,4-butane sultone followed by the reaction with HCl. MWCNT-BuSO 3 H was used as a heterogeneous catalyst for one-pot Knoevenagel condensation, Michael addition, and cyclodehydration of dimedone with various aromatic aldehydes at room temperature (Scheme 1).…”

The Use of Supported Acidic Ionic Liquids in Organic Synthesis

“…Supported dual acidic ILs were also obtained from polymers incorporating heterocyclic moieties, such as poly(4-vinylpyridine) [67,68] or a melamine resin [69]. The reaction of the heterocycles with 1,4-butanesultone led to a zwitterionic structure that was converted to the IL with sulphuric acid (Scheme 16).…”

“…In case of Brønsted acidic SILPs, activation of substrates is thought to proceed either via protonation (Figure 4A) [39,43,51,53,56,58,62,63] or via hydrogen bond formation, without assuming a real proton transfer from the catalyst to the substrate (Figure 4B) [46,47,48,54,55,57,64,67,68] in the presence of [HSO 4 ] − anions [46,47,48,51,63], SO 3 H-functionalised cations [43,53,54,56], or both [39,55,57,58,62,64,67,68].…”

“…A dual Brønsted acidic IL ([(HSO 3 ) 4 C 4 pyr]HSO 4 ) supported on poly(4-vinylpyridine) was applied in the synthesis of 4,4'-(arylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol)s ( 9 , Scheme 26) [67]. Even acid sensitive aldehydes, such as 2-furyl and 2-thienyl carbaldehyde, were smoothly converted into the corresponding products in 90%–97% yields in less than an hour in ethanol reflux.…”