Ruli Borah

Henry reaction in environmentally benign methods using imidazole as catalyst

Abstract Imidazole has been found to be an efficient Lewis base catalyst for the synthesis of 2-nitroalkanols from nitro-aldol reaction in aqueous medium as well as using solvent-free grinding methods. In both cases, the products have been found in good to moderate yields without formation of any side product. Recycling of the catalyst is also possible with imidazole containing aqueous phase reaction medium (after extraction of product).

Synthesis of dibenzoxanthene and acridine derivatives catalyzed by 1,3-disulfonic acid imidazolium carboxylate ionic liquids

New members of 1,3-disulfonic acid imidazolium carboxylate ionic liquids [DSIM][X] (where X = [CH3COO]−, [CCl3COO]−, [CF3COO]−) were prepared and characterized by 1H NMR,13C NMR, FT-IR, TGA,UV-vis and elemental analysis. The more acidic ILs [DISM][CCl3COO] and [DSIM][CF3COO] were efficiently utilized as recyclable catalysts for the preparation of 14H-dibenzo[a,j]xanthene and 1,8-dioxo-decahydroacridine derivatives in short times under solvent-free conditions at 80–100 °C with excellent yields. The above two ILs could be effectively utilized as catalysts for the synthesis of 1,8-dioxo-decahydroacridine in water at the same temperature.

Aza-Michael Addition of Amines to α,β-Unsaturated Compounds Using Molecular Iodine as Catalyst

Aza-Michael adducts are obtained in very good yields by the conjugate addition of aliphatic amines to α,β-unsaturated compounds using molecular iodine as catalyst in dichloromethane at room temperature. Aromatic amines were found to be reactive under reflux in toluene.

Imidazole-Catalyzed Henry Reactions in Aqueous Medium

Abstract 2-Nitroalkanols can be efficiently synthesized using imidazole as a mild Lewis basic catalyst in aqueous medium as well as in organic solvents. The products have been found in good yields without purification (> 95% purity by 1H NMR) for aromatic aldehydes. Additionally, the very mild reaction conditions prevent the particular side reactions such as aldol condensation, Cannizzaro reaction, or dehydration of the 2-nitro alcohols into nitro alkenes even if aromatic aldehydes are used. This report satisfies the criteria for green synthesis in terms of reaction medium and recycling of the catalyst (imidazole).

Synthesis of anti-2,3-dihydro-1,2,3-trisubstituted-1H-naphth [1,2-e][1,3]oxazine derivatives via multicomponent approach

A series of anti-2,3-dihydro-1,2,3-trisubstituted-1H-naphth [1,2-e][1,3]oxazine derivatives 6 were exclusively obtained in high yields for the first time through multicomponent reactions (MCRs) of 2-naphthol, aromatic aldehydes and electron rich primary amines in ethanol at room temperature using CCl3COOH as catalyst. The same reaction could be conducted effectively in solvent-free medium at 100 °C. The stereochemistry of the two hydrogens connected to C-2 and C-4 (1,3) positions of the oxazine ring are identified as anti-orientation by single crystal XRD, COSY and NOESY analysis.

Green Synthesis of Tetraalkylammonium Tribromide using Cerium(IV) Ammonium Nitrate (CAN) as Oxidant

Abstract Cerium(IV) ammonium nitrate (CAN) mediates oxidation of tetraalkylammonium bromide to tetraalkylammonium tribromide in greener reaction conditions using water as solvent. The procedure is simple, convenient, and environmentally benign for the synthesis of tetraalkylammonium tribromide with great yields.

Synthesis of 1,3-Dioxanes Catalyzed by TsOH-SiO2 Under Solvent-Free Conditions

Abstract Silica-supported p-toluene sulfonic acid is found to be an excellent catalyst for the Prins reaction to produce 1,3-dioxanes in good yields from olefins and aliphatic aldehydes in dichloromethane at room temperature and solventless microwave irradiation within a short reaction time.

Dual nature of polyethylene glycol under microwave irradiation for the clean synthesis of oximes

Polyethylene glycol (PEG-400 and PEG-600) is an efficient, inexpensive, and recyclable homogeneous medium and catalyst (dual nature) for the clean synthesis of oximes (and aldoximes) under microwave irradiation in the absence of acid and base catalysts. Both aliphatic and aromatic aldehydes/ketones give satisfactory results under microwave irradiation within a short time.Graphical abstract

Studies on –SO3H functionalized Brønsted acidic imidazolium ionic liquids (ILs) for one-pot, two-step synthesis of 2-styrylquinolines

ABSTRACT Four task-specific –SO3H functionalized imidazolium ionic liquids (ILs) were investigated for Brønsted acidities by Hammett functions. After knowing their thermal stabilities, the catalytic activity was observed for the preparation of 2-styrylquinolines by following consecutive Friedländer and Knoevenagel reactions in solvent-free thermal energy. The acidity order ([Dsim][OOCCF3] > [Dsim][OTs] > [Dsim][OOCCl3] > [Msim][OOCCF3]) of three ILs was consistent with their activity order observed in the acid-catalyzed synthesis of 2-styrylquinolines under solvent-free conditions at 90° C, with the exception of [Dsim][OTs]. The best catalytic activity was shown by 25 mol% of [Dsim][OOCCF3] IL. The less acidic IL required 50 mol% to give good yield of 2-styrylquinolines under the optimized condition. GRAPHICAL ABSTRACT

Design and Exploration of –SO3H Group Functionalized Brønsted Acidic Ionic Liquids (BAILs) as Task-Specific Catalytic Systems for Organic Reactions: A Review of Literature

For several decades various chemical industries are involved in environment pollution by using hazardous chemicals or excessive use of solvents or catalysts to get maximum amount of desired product. In this case acidic ionic liquids may act as safer substitute of volatile organic solvents/or traditional Brønsted or Lewis acid catalysts with their unique dual task-specific solvent-catalyst properties. Recent surge in the literature review clearly describes the importance, properties and applications of acidic ionic liquids as solvent and efficient reusable catalyst in organic reactions. This review presents an account of some recent reports indicating the synthesis and uses of –SO3H functionalized ionic liquids(SFILs) as catalyst in organic synthesis.