Ionic liquid‐functionalized mesoporous silica nanoparticles ([pmim]FeCl₄/MSNs): Efficient nanocatalyst for solvent‐free synthesis of N,N′‐diaryl‐substituted formamidines

Abstract

We report the synthesis of ionic liquid‐functionalized mesoporous silica nanoparticles ([pmim]FeCl4/MSNs) via a method of post‐grafting on parent MSNs. This hybrid material was characterized using scanning and transmission electron microscopies, energy‐dispersive X‐ray spectroscopy, nitrogen adsorption–desorption analysis, Fourier transform infrared spectroscopy, powder X‐ray diffraction and thermal analyses. The material was utilized as an efficient heterogeneous catalyst for the synthesis of N,N′‐diaryl‐substituted formamidines through the reaction of triethyl orthoformate with arylamines under solvent‐free conditions. The catalyst was recovered easily and reused several times without significant loss of its catalytic activity.

Preparation of Fe3O4@C‐dots as a recyclable magnetic nanocatalyst using Elaeagnus angustifolia and its application for the green synthesis of formamidines

“…Lastly, the loss of EtOH from activated intermediate resulted in the production of N , N ′‐diarylformamidines. [ 63,65 ]…”

“…Although the listed protocols in Table 3 are doubtlessly capable of significantly improving the synthesis of formamidines, however, one or more disadvantages can be observed in some of them that include long reaction time (Table 3, entries 1, 4-7, 9, and 10), the existence of solvent (Table 3, entries 1, 2, and 6), and low yields (Table 3, entry 4). Nonetheless, the catalytic system introduced by this work consists certain benefits such as low cost, non-toxicity, short reaction time, and satisfying [61] 2 30 100 92 138-140 139-141 [61] 3 40 100 90 178-180 180-182 [63] 4 40 100 88 184-186 186-187 [63] 5 30 100 85 198-200 198-200 [65] 6 50 100 80 117-119 118-120 [76] [62] 11 -9 (h) 100 ---yields. Furthermore, the recovery of this catalyst from the reaction mixture can be simply performed through the application of an external magnet to be stored and reused.…”

“…[54] However, other available techniques require the utilization of varying starting materials, including acid chlorides, [55] aldehydes, [56,57] O-dinitrobenzene, [58] gold's reagent, [59] and 2-nitro aniline. [60] Nevertheless, for the advancement of this protocol, various varying investigations have been done on catalytic systems to improve this process, which includes nanoporous TiO 2 containing an ionic liquid bridge, [61] β-cyclodextrin, [62] periodic mesoporous organo-silica containing bridged N-sulfonic acid groups, [63] hexafluoroisopropanol as a solvent/catalyst, [64] ionic liquid-functionalized mesoporous silica nanoparticles, [65] cerium (IV) ammonium nitrate, [66] sulfonated rice husk ash, [67] γ-Fe 2 O 3 @SiO 2 -HBF 4 , [68] and MCM-41-SO 3 H mesoporous zeolite. [69] Although the mentioned protocols have enhanced the synthesizing process of these compounds, however, most of them are limited by certain factors, including long reaction time, high temperatures, expensive reagents, strong acidic conditions, by-products formation, toxic organic solvents, multistep sequences, usage of an inorganic metal catalyst, difficult recovery of catalyst, and poor yields of the products.…”

“…[ 54 ] However, other available techniques require the utilization of varying starting materials, including acid chlorides, [ 55 ] aldehydes, [ 56,57 ] O ‐dinitrobenzene, [ 58 ] gold's reagent, [ 59 ] and 2‐nitro aniline. [ 60 ] Nevertheless, for the advancement of this protocol, various varying investigations have been done on catalytic systems to improve this process, which includes nanoporous TiO 2 containing an ionic liquid bridge, [ 61 ] β‐cyclodextrin, [ 62 ] periodic mesoporous organo‐silica containing bridged N‐sulfonic acid groups, [ 63 ] hexafluoroisopropanol as a solvent/catalyst, [ 64 ] ionic liquid‐functionalized mesoporous silica nanoparticles, [ 65 ] cerium (IV) ammonium nitrate, [ 66 ] sulfonated rice husk ash, [ 67 ] γ‐Fe 2 O 3 @SiO 2 –HBF 4 , [ 68 ] and MCM‐41‐SO 3 H mesoporous zeolite. [ 69 ]…”

CuI/Fe3O4 NPs@Biimidazole IL‐KCC‐1 as a leach proof nanocatalyst for the synthesis of imidazo[1,2‐a]pyridines in aqueous medium

“…Based on their significant properties such as high ionic conductivity, excellent thermal stability, ecofriendly, stability, and wide liquid temperature range window, ILs have been used for the organic synthesis. [7,8] Various types of ILs that grafted to different supports not only can be used as reaction media and catalysis but also can be stabilized various nanoparticles because of their coordination and electrostatic interactions with ions and metal atoms. [9] Also, during the reaction procedure, the supported ILs can provide appropriate hydrophobic media and enhance the catalytic activity of the catalyst.…”