[bmim]HSO4: an efficient and reusable catalyst for one-pot three-component synthesis of 2,3-dihydro-4(1H)-quinazolinones

Abstract

Various di- and mono-substituted quinazolinones were synthesized by one-pot condensation of isatoic anhydride, aldehyde and amine, or ammonium carbonate using [bmim]HSO₄ as catalyst in aqueous medium. Water as a reaction media, recyclability of catalyst, shorter reaction time, and good yields (70–90%) are some of the salient features of the developed protocol.     

Non-catalytic condensation of aromatic aldehydes with aniline in high temperature water

Abstract

The synthesis of diamino triphenyl methanes from aniline and aromatic aldehydes was conducted in near critical water and supercritical water. The reaction parameters, such as temperature, density, and reaction time, have been studied. Significant acceleration of the condensation reaction of aniline and aromatic aldehydes can be achieved by using high temperature water, especially near the critical point, in the absence of any acid catalysts. It has been demonstrated that high temperature water act effectively in the place of conventional acid catalysts.     

Graphene‐Based Composite with γ‐Fe2O3 Nanoparticle for the High‐Performance Removal of Endocrine‐Disrupting Compounds from Water

Graphene is a 2D sp²‐hybridized carbon sheet and an ideal material for the adsorption‐based separation of organic pollutants. However, such potential applications of graphene are largely limited, owing to their poor solubility and extensive aggregation properties through graphene? graphene interactions. Herein, we report the synthesis of graphene‐based composites with γ‐Fe₂O₃ nanoparticle for the high‐performance removal of endocrine‐disrupting compounds (EDC) from water. The γ‐Fe₂O₃ nanoparticles partially inhibit these graphene? graphene interactions and offer water dispersibility of the composite without compromising much of the high surface area of graphene. In their dispersed form, the graphene component offers the efficient adsorption of EDC, whilst the magnetic iron‐oxide component offers easier magnetic separation of adsorbed EDC.     

Promotion effect of adsorbed water/OH on the catalytic performance of Ag/activated carbon catalysts for CO preferential oxidation in excess H2

Activated carbon (AC) supported silver catalysts were prepared by incipient wetness impregnation method and their catalytic performance for CO preferential oxidation (PROX) in excess H₂ was evaluated. Ag/AC catalysts, after reduction in H₂ at low temperatures (≤200 °C) following heat treatment in He at 200 °C (He200H200), exhibited the best catalytic properties. Temperature-programmed desorption (TPD), X-ray diffraction (XRD) and temperature-programmed reduction (TPR) results indicated that silver oxides were produced during heat treatment in He at 200 °C which were reduced to metal silver nanoparticles in H₂ at low temperatures (≤200 °C), simultaneously generating the adsorbed water/OH. CO conversion was enhanced 40% after water treatment following heat treatment in He at 600 °C. These results imply that the metal silver nanoparticles are the active species and the adsorbed water/OH has noticeable promotion effects on CO oxidation. However, the promotion effect is still limited compared to gold catalysts under the similar conditions, which may be the reason of low selectivity to CO oxidation in PROX over silver catalysts. The reported Ag/AC-S-He catalyst after He200H₂00 treatment displayed similar PROX of CO reaction properties to Ag/SiO₂. This means that Ag/AC catalyst is also an efficient low-temperature CO oxidation catalyst.     

Deprotection of Oximes using Iodosobenzene in the Presence of β‐Cyclodextrin in Water

A mild and efficient method for the regeneration of carbonyl compounds from oximes at room temperature in impressive yields has been developed using iodosobenzene/KBr in the presence of β‐cyclodextrin in water.     

Enantioselective synthesis of spiro[4H-pyran-3,3′-oxindole] derivatives catalyzed by cinchona alkaloid thioureas: Significant water effects on the enantioselectivity

An efficient stereoselective three-component reaction for the synthesis of functionalized spiro[4H-pyran-3,3′-oxindole] derivatives was realized through an organocatalyzed domino Knoevenagel/Michael/cyclization reaction using a cinchonidine-derived thiourea as the catalyst. Using water as the additive was found to improve the product ee values significantly. Under the optimized conditions, the reactions between isatins, malononitrile, and 1,3-dicarbonyl compounds yield the desired spirooxindole products in good yields (71–92%) and moderate to high ee values (up to 87% ee).     

A metal-free approach to access ketones,amides, and nitriles employing TBAI/TBHP oxidative system in water

Hydrocarbons, benzylamines, and heteroaromatic-bearing amines have been efficiently employed as substrates in allylic and benzylic oxidations via C(sp3)–H bond activation by TBAI/TBHP in water. This operationally simple method allows access to ketones, nitriles, and amides in moderate to high yields and a regio- and chemoselective late-stage functionalization.     

Perchloric Acid-Catalyzed Synthesis of 9-Aryl Xanthenes-9H-3,6-diol and 1,3,6,8-Tetraol in Water

Efficient syntheses of xanthenes have been described using a catalytic amount of perchloric acid in water. The high temperature and lengthy reaction time normally required for formation of xanthenes derivatives are not necessary when using a catalytic amount of perchloric acid. The method is relatively inexpensive, easily available, nonvolatile, nonexplosive, and thermally robust to catalyze the reaction at 80 °C by simple heating with good to excellent yields. The advantages of the reaction involve simple reaction protocol, simple workup, and improved synthesis in the presence of perchloric acid as catalyst.     

Microwave Synthesis of 5-Substituted 1H-Tetrazoles Catalyzed by Bismuth Chloride in Water

Bismuth chloride was used to catalyze the [2 + 3] cycloaddition between sodium azide with aryl nitriles, aliphatic nitriles, and vinyl nitriles. A number of 5-substituted 1H-tetrazoles were synthesized in water or isopropanol/water mixtures using microwave heating. Good yields were obtained for these reactions when heated for 1 h at 120–160 °C in a 3:1 isopropanol/water mixture. A few of the less reactive nitriles required longer reaction times for good yields.     

Practical Approach for Synthesis of 2-Amino-benzoxazole in Water

A practical copper-catalyzed amination of benzoxazole with secondary amine in water has been developed. This reaction has proved to be effective to some cyclic amines, and the substituted group of nitrogen has a great impact on the amination reaction. A copper-catalyzed/ amine-induced ring opening of the benzoxazole and recyclization/oxidation mechanism was also proposed.