Silica boron–sulfuric acid nanoparticles (SBSANs): preparation, characterization and their catalytic application in the Ritter reaction for the synthesis of amide derivatives

Abstract

Among a number of different heterogeneous and homogeneous catalysts, silica boron-sulfuric acid nanoparticles (SBSANs) with both protic and Lewis acidic sites were shown to be the most active and recyclable catalyst in the Ritter reaction. Various amide derivatives were synthesized from alcohols and nitriles via a one-step and easy process in the presence of a catalytic amount of SBSAN at room temperature in solvent free conditions with excellent isolated yields. The silica boron-acid nanoparticles (SBANs) were regularly synthesized during the modification of the silica support by boric acid [B(OH) 3 ] during the chemical vapor deposition (CVD) process and subsequently, this material was reacted with chlorosulfonic acid (ClSO 3 H) to obtain the SBSAN catalyst. The new catalyst was characterized using some different microscopic and spectroscopic techniques such as patterned X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), FT-Raman spectrometry and FT-IR spectroscopy. Thermal behavior of the SBSAN catalyst was also investigated by a thermogravimetric (TG) analyzer.

Nano silica boron sulfuric acid as a dual Brønsted/Lewis acid and a heterogeneous catalyst in Baeyer–Villiger oxidation of ketones with hydrogen peroxide

“…The symmetric stretching vibration of O=S=O is seen at *1168 cm -1 . The very broad and intense O-H stretching absorption band appears in the region of 3366 cm -1 [22,23]. As clearly seen, the FT-IR spectrum gives a good indication of the successful preparation of NSBSA (Fig.…”

“…A comparison between the XRD pattern of both nano silica and NSBSA shows that two significant peaks are positioned at 2h = 25.09°and 27.91°, which is related to the presence of Si-O and B-O bonds in the crystalline structure of NSBSA, respectively (Fig. 3) [22].…”

“…So, the drastic reduction of the catalytic activity of NSBSA, especially in coordinating solvents, guided us to conclude that the catalytic activity of NSBSA depends on both sulfuric (OSO 3 H) and boron sites. Moreover, bonding of each boron atom with at least two electron withdrawing groups (OSO 3 H), may increase its Lewis acidity character more efficiently [22,26]. Therefore, among a variety of examined solvents, based on the results of Table 2, chloroform was selected as the ideal solvent in these series because the B-V oxidation of ketones proceeded more smoothly.…”

“…So, two more practical strategies applied to overcome its drawbacks: (i) applying an acidic catalyst to improve the electrophilicity of the carbonyl group of ketone to compensate the weakness of the nucleophilicity of hydrogen peroxide, (ii) using a base to deprotonate or polarized the O-H bonds of hydrogen peroxide to improve its nucleophilicity toward the carbonyl group of ketone. In recent years, heterogeneous catalysts, chiefly solid acids and especially those based on micelle-templated silica and other mesoporous high surface area support materials, play a more serious roles in acid-catalyzed chemical transformations because of their good catalytic activities, high efficiency and selectivity, reusability, simple separation from the reaction mixture and also less environmentally impacts, as important principles of green chemistry [16][17][18][19][20][21][22]. It is shown that nano silica boron sulfuric acid (NSBSA), which is considered as a dual Brønsted/Lewis acid and also an eco-friendly nano-heterogeneous catalyst, has an effective role in performing acid-base catalyzed organic transformations [22].…”

6.07 Ritter-Type Reactions

“…183 Catalytic quantities of p-toluenesulfonic acid permit the conversion of symmetrical acyclic carboxylic anhydrides into their corresponding unsymmetrical imides. Typically, 30 mol% of acid was employed for liquid nitriles and 50 mol% for solid nitriles.…”