H. Maheswaran

Gold nanoparticles stabilized on nanocrystalline magnesium oxide as an active catalyst for reduction of nitroarenes in aqueous medium at room temperature

Gold nanoparticles deposited on nanocrystalline magnesium oxide is a very efficient catalyst for the reduction of nitroarenes in aqueous medium at room temperature. Sodium borohydride is used as the source of hydrogen for the reduction of nitro groups. This catalytic system selectively reduces the nitro group even in the presence of other sensitive functional groups under very mild conditions in good to excellent yields without the requirement of any promoters. The reaction kinetics of reduction of 4-nitrophenol to 4-aminophenol has been studied by UV-visible spectrophotometry, and its apparent rate constant has been determined and compared with those of other supported gold catalysts. The spent heterogeneous catalyst is recovered by simple centrifugation, and reused for multiple cycles.

Nanocrystalline magnesium oxide stabilized gold nanoparticles: an advanced nanotechnology based recyclable heterogeneous catalyst platform for the one-pot synthesis of propargylamines

A simple and elegant synthesis of gold nanoparticlesvia counter ion stabilization of AuCl4− on nanocrystalline magnesium oxide support followed by sodium borohydride reduction is described here. A thorough characterization of the resulting heterogeneous material revealed the presence of uniformly distributed gold nanoparticles (10–12 nm) deposited on to (111) plane of quasi-crystalline icosahedral lattice of nanocrystalline magnesium oxide which exhibits excellent catalytic activity for the one pot synthesis of structurally divergent propargylamines via a three component coupling of an alkyne, an amine and an aldehyde without requiring any additives or inert atmosphere. The catalyst contains ultra low loading of gold (0.236 mol%), and turnover numbers as high as 400 are obtained. The catalyst can be isolated by simple centrifugation and reused for four cycles.

N4-tetradentate dicarboxyamidate/dipyridyl palladium complexes as robust catalysts for the Heck reaction of deactivated aryl chlorides.

Structurally well defined and thermally stable Pd(II) complexes, derived from N4-tetradentate dicarboxyamide/dipyridyl ligands, were evaluated as catalysts for the Heck reactions of deactivated aryl chlorides and olefins (see scheme). The concept of using an anionic carboxyamide as an ancillary ligand for palladium demonstrated here provides a new opportunity for the development of phosphine-free transition-metal catalysis.

Ullmann coupling of aryl iodides catalyzed by gold nanoparticles stabilized on nanocrystalline magnesium oxide

Gold nanoparticles stabilized on nanocrystalline magnesium oxide is shown to be an efficient heterogeneous catalytic system for the synthesis of symmetrical biaryls via homocoupling of aryl iodides.

Sulfonic acid resin and copper salts: a novel heterogeneous catalytic system for direct hydroxylation of haloarenes

A sulfonic acid resin (INDION-770) in combination with Cu salts is demonstrated to be a versatile heterogeneous catalyst for direct hydroxylation of haloarenes to give corresponding phenols in excellent yields.

Sulfonic acid containing cation-exchanger resin “INDION-770” and copper(I) salts: a novel reusable catalyst for N-arylation of NH-heterocycles with haloarenes

Industrial grade sulfonic acid based cation-exchanger resin “INDION-770” in combination with Cu(I) salts is demonstrated to be a versatile heterogeneous catalytic system for direct N-arylation of NH-heterocycles with various haloarenes to give the corresponding N-arylheterocycles in good to excellent yields.

PhI(OCOCF3)2-mediated ruthenium catalyzed highly site-selective direct ortho-C–H monoarylation of 2-phenylpyridine and 1-phenyl-1H-pyrazole and their derivatives by arylboronic acids

We report a concise, versatile, and practical method for PhI(OCOCF3)2 mediated direct ortho C–H monoarylation of 2-phenylpyridine and its derivatives and 1-phenyl-1H-pyrazoles via Ru catalyzed reaction. The significant advantage of this transformation is the creation of highly site selective C–C bond by using arylboronic acids as arylating agent under mild reaction conditions.

Stereoselective asymmetric hydrogenation of 2-benzamidomethyl-3-oxobutanoate catalyzed by Pregosin's hydrido complexes of type Ru(H)(p-cymene)(bis-phosphine)(SbF6)

Pregosins complex Ru(H)(p-cymene)((R)-DTBM-Segphos)(SbF6) has been shown to be an efficient catalyst for stereoselective asymmetric hydrogenation of 2-benzamido-methyl-3-oxobutanoate to syn-(2S,3R)-methyl-2-(benzamido-methyl)-3-hydroxybutanoate in high diastereoselectivity and enantioselectivity in ethanol.

Highly meta-selective halogenation of 2-phenylpyridine with a ruthenium(I) catalyst

We report a concise, versatile, and practical method for PhI(OCOCF3)2 mediated direct meta-C–H monohalogenation of 2-phenylpyridine and its derivatives via an Ru(I)-catalyzed reaction. The significant advantage of this transformation is the creation of a highly site-selective C–X bond by using NXS as halogenating agents under mild reaction conditions.