Brindaban C. Ranu

Indium Metal and Its Halides in Organic Synthesis

This review highlights the applications of indium metal and indium(III) halides in organic synthesis with particular reference to regio-, stereo-, and chemoselectivity. Indium-mediated reactions include the regioselective allylation of alkynes, the stereoselective debromination of vic-aryl-substituted dibromides, the homocoupling of alkyl/aryl halides, and the reduction of α-halocarbonyl compounds. Indium trichloride has been used as a Lewis acid catalyst in epoxide rearrangements, in the synthesis of α-amino phosphonates, and in the construction of the quinoline system. Indium triiodide has proven to be a very efficient catalyst for transesterification processes.

Highly Chemoselective Reduction of Aromatic Nitro Compounds by Copper Nanoparticles/ Ammonium Formate

A highly chemoselective reduction of aromatic nitro compounds to the corresponding amino derivatives has been achieved by a combination of copper nanoparticles and ammonium formate in ethylene glycol at 120 degrees C. The reductions are successfully carried out in presence of a wide variety of other reducible functional groups in the molecule, such as Cl, I, OCH2Ph, NHCH2Ph, COR, COOR, CN, etc. The reactions are very clean and high yielding.

Catalysis by an ionic liquid: efficient conjugate addition of thiols to electron deficient alkenes catalyzed by molten tetrabutylammonium bromide under solvent-free conditions

An inexpensive and readily available ionic liquid, tetrabutylammonium bromide in the molten state, efficiently catalyzes the conjugate addition of thiols to α,β-unsaturated nitriles, carboxylic ester, ketones and aldehydes as well as nitro olefins.

Copper Nanoparticle-Catalyzed CarbonCarbon and CarbonHeteroatom Bond Formation with a Greener Perspective

The carbon-carbon and carbon-heteroatom bond formations constitute the backbone of organic synthesis and have been widely used in the synthesis of natural products and useful compounds. Because of growing environmental concern, more attention has been focussed on the development of greener methods. Copper is environment-friendly and comparatively inexpensive. Although the use of copper salts in catalysis has been known since the last century, this area of research has been less explored compared to other metals, such as palladium, magnesium, and zinc. This review highlights the general features of nanoparticles as catalysts with particular reference to copper and the recent developments in the copper(0) nanoparticle-catalyzed C(aryl)-C(aryl/alkynyl), C(aryl)-N, C(aryl)-O, C(aryl)-S, and C(aryl)-Se bond formations and related reactions. The mechanisms of the reactions have been outlined and discussed with respect to the active catalytic species and possible intermediates. The scope, limitations, and green aspects of the reactions have also been highlighted. The convenient methods of preparation of copper nanoparticles and their characterization are described.

Microwave-assisted simple synthesis of quinolines from anilines and alkyl vinyl ketones on the surface of silica gel in the presence of indium(III) chloride

A simple and efficient procedure has been developed for the synthesis of 4-alkylquinolines by a one-pot reaction of anilines with alkyl vinyl ketones on the surface of silica gel impregnated with indium(III) chloride under microwave irradiation without any solvent.

Indium trichloride catalyzed one-step synthesis of α-amino nitriles by a three-component condensation of carbonyl compounds, amines and potassium cyanide

A simple and general method has been developed for the synthesis of α-aminonitriles by a one-pot three-component condensation of aldehydes or ketones, amines and potassium cyanide in THF in presence of a catalytic amount of indium trichloride.

Solvent-free one-pot synthesis of 1,2,3-triazole derivatives by the ‘Click’ reaction of alkyl halides or aryl boronic acids, sodium azide and terminal alkynes over a Cu/Al2O3 surface under ball-milling

A one-pot procedure for the synthesis of 1,2,3-triazole derivatives by a three-component coupling of alkyl (benzyl) halides or aryl boronic acids, sodium azide and terminal alkynes over copper(II) sulfate supported on alumina (Cu/Al2O3) under ball-milling in the absence of any solvent and additive has been developed. The product was isolated by simple washing of the crude reaction residue with ethanol followed by evaporation of the solvent. No chromatographic purification is required. The catalyst is recycled for subsequent reactions. The azides are produced in situ and thus this procedure avoids the handling of hazardous azides. This protocol offers broad scope for access to a variety of diversely substituted 1,2,3-triazoles. The use of no hazardous organic solvent, the use of ball-milling, and cost efficiency, recyclability of the catalyst up to eight runs without appreciable loss of activity and high yields of products make this procedure greener.

Efficient microwave-assisted synthesis of quinolines and dihydroquinolines under solvent-free conditions

A convenient and efficient procedure for the synthesis of quinolines and dihydroquinolines has been developed by a simple one-pot reaction of anilines with alkyl vinyl ketones on the surface of silica gel impregnated with indium(III) chloride under microwave irradiation without any solvent.

Remarkable influence of substituent in ionic liquid in control of reaction: simple, efficient and hazardous organic solvent free procedure for the synthesis of 2-aryl benzimidazoles promoted by ionic liquid, [pmim]BF4

A simple and efficient procedure for the synthesis of 2-substituted benzimidazoles has been developed by a one-pot reaction of o-phenylenediamine with aromatic aldehydes in the presence of an ionic liquid, 1-methyl-3-pentylimidazolium tetrafluoroborate, [pmim]BF4 at room temperature in open air without any organic solvent. The ionic liquid is recycled. A remarkable influence of the substituent on the imidazolium unit of the ionic liquid on the outcome of the reaction is observed.

A simple and green procedure for the synthesis of α-aminophosphonate by a one-pot three-component condensation of carbonyl compound, amine and diethyl phosphite without solvent and catalyst

A simple, general, efficient and greener method has been developed for the synthesis of α-aminophosphonates through a solvent-free and catalyst-free one-pot three-component condensation of carbonyl compound, amine and diethyl phosphite.