Ordered Hexagonal Mesoporous Aluminosilicates and their Application in Ligand‐Free Synthesis of Secondary Amines

Abstract

A new facile synthesis of ordered mesoporous aluminosilicates has been developed and applied for the efficient catalytic synthesis of N-benzyl secondary amines under ligand and basefree conditions. The MAS(38) catalyst with a well-ordered mesoporous structure and strong acidic sites was used for acid-catalyzed organic transformations and its operational simplicity and ease of its isolation procedure make it an attractive alternative to current methodologies. N-alkyl secondary amine derivatives linked to herbicides and pharmaceuticals have been demonstrated as numerous biologically active compounds for drug discovery.[1] N-benzyl secondary amines, in particular, have attracted considerable attention from both biological and organic chemists. This is because they appear as carboxamide derivatives, which are the most prevalent structural moieties in medicinal chemistry.[2] However, despite widespread interest, the most common strategies for the production of secondary amines such as electrophilic alkylation, reductive alkylation, and amination of aryl halides, often exhibit limitations such as low selectivity toward desired secondary amines, harsh reaction conditions, and stoichiometric amounts of wasteful salts. [3,4] In addition, various expensive [Ru 3 (CO) 7 ] cluster, [Ir(COD)Cl] dimer, rhodium, and platinum transition metal complexes have been used as homogeneous catalysts for synthesizing secondary amines in the presence of base additives, which retard the commercialization of the process because of high cost and environmental concerns. [5][6][7] The use of heterogeneous catalysts [8][9][10][11][12] offers several advantages over homogeneous catalysts, including ease of separating reactants, minimal trace metal in the products, ease of handling, process control, and reusability of catalysts. These advantages can thus improve reaction processes. Therefore, developing an environmentally friendly and recyclable heterogeneous catalytic system for synthesizing secondary amines is of considerable interest. Heterogeneous catalysts such as Fe/ amino acids, Fe 3 O 4 , and Fe 3 O 4 /tBuO À have been used for the synthesis of secondary amines, [12,13] however, these systems suffer from complicated synthesis procedures and low activity compared with precious metal complexes.In recent years, mesoporous materials have demonstrated their potential in solar cells, fuel cells, and drug delivery systems. [14][15][16][17][18][19][20][21] In addition, mesoporous materials have been increasingly applied as heterogeneous catalysts in various organic transformations because of their unique structural and textural properties such as controllable pore size, uniform poresize distribution, high thermal stability, and ultrahigh specific surface area. [22,23] Among various heterogeneous catalysts, aluminosilicates have been considered useful solid catalysts because of their usage as effective catalysts in aldol, FriedelCrafts, and Diels-Alder reactions. [24,25] However, based on our knowledge, no studies have synthesized secondary amin...

Mesoporous Shell@Macroporous Core Aluminosilicates as Sustainable Nanocatalysts for Direct N‐alkylation of Amines

“…The intact core and shell morphology is maintained even after five cycles of catalytic reaction as evident from the TEM images (ESI Figure 10) of the spent catalyst. The conversion and selectivity demonstrated by MMAS‐40 catalyst under milder temperatures is better or on par with the previously reported heterogeneous catalysts,, or carried out by homogeneous route ,. It should be noted here that on MMAS‐40 nanocatalyst, direct N‐alkylation protocol works in the absence of any special kind of ligands like phosphines, pincer complexes or costly metal salts.…”

“…Here, there is an enhancement in catalytic activity in terms of reaction time as well as the product yield. This enhancement in catalytic activity observed in our present methodology is noteworthy as well as beneficial since electron deficient nucleophiles are generally considered to be difficult substrates for the direct N‐alkylation of anilines ,…”

“…From the point of view of the starting materials and products, the reaction resembles that of hydrogen borrowing chemistry; but the presence of acidity leads the reaction in an alternate pathway where Bronsted acidity catalyse the reaction. A similar approach towards the secondary amine synthesis is previously reported in literature ,. In these cases, catalyst synthesis method involve hydrothermal process with longer catalyst synthesis time, higher reaction temperature and less yield with poorly nucleophilic anilines.…”

On the Gas Storage Properties of 3D Porous Carbons Derived from Hyper-Crosslinked Polymers

“…In the following these solids are referred to as UPO (from University of Piemonte Orientale). UPO materials, prepared from tetraphenylmethane (TPM) and formaldehyde dimethyl acetal (FDA), represent a very attractive family of porous organic networks easily prepared by Friedel–Crafts reaction (Figure 1); in general, HCPs combine high gas uptake capacity, low synthetic costs, and easy industrial scalability [58,59,60,61,62,63].…”

Synthesis of Porous Organic Polymer-Based Solid-Acid Catalysts for 5-Hydroxymethylfurfural Production from Fructose

“…In the 19th century, HMF was first separated from a reaction mixture of fructose, sucrose, and oxalic acid, and is currently produced by dehydration of monosaccharides. Solid acid catalysts (such as zeolites, metal oxides, phosphate/phosphonates, sulfuric acid) [8][9][10][11][12][13] and mineral acids like (HCl, H 2 SO 4 , H 3 PO 4 ) [14][15][16] have been reported by many research groups as catalysts for the successful synthesis of HMF. Solid acid catalysts are advantageous above mineral acids since they are non-corrosive, non-toxic, eco-friendly, and diminish other environmental problems related to mineral acids.…”