Kasi Pitchumani

Syntheses of 5-substituted 1H-tetrazoles catalyzed by reusable CoY zeolite.

A simple and efficient route for the synthesis of 5-substituted 1H-tetrazoles catalyzed by CoY zeolite is reported. The salient features of this atom-economical, cost-effective, and high-yield cobalt-catalyzed protocol are aerobic conditions, lower reaction time, and milder reaction conditions without additives. Other advantages include experimental ease of manipulation, safer alternative to hazardous, corrosive, and polluting conventional Lewis acid catalysts, recovery, and reusability with consistent catalytic activity. The results are rationalized by proposing a suitable mechanism.

Palladium nanoparticles supported on triazine functionalised mesoporous covalent organic polymers as efficient catalysts for Mizoroki–Heck cross coupling reaction

A novel class of mesoporous covalent organic polymer (MCOP) was synthesised by the nucleophilic substitution of cyanuric chloride with 4,4′-dihydroxybiphenyl. The MCOP was fully characterized using powder X-ray diffraction analysis, Fourier transform infrared spectroscopy, 13C-solid state NMR spectroscopy, field emission scanning electron microscopy and thermogravimetric analysis. These nitrogen rich materials act as good supports for palladium nanoparticles (Pd NPs) and exhibit excellent catalytic activity towards Mizoroki–Heck cross coupling between aryl bromides and alkenes. Hot filtration tests demonstrate that the presence of the triazine rings on the polymers is beneficial for enhancing the stability of Pd NPs. The polymers are also cheap, easy to synthesise and can be recycled up to five times with only a minor loss of activity.

Per-6-amino-β-cyclodextrin as an Efficient Supramolecular Ligand and Host for Cu(I)-Catalyzed N-Arylation of Imidazole with Aryl Bromides

Per-6-amino-beta-cyclodextrin (per-6-ABCD), acting simultaneously as a supramolecular ligand for CuI and host for aryl bromides, catalyzes N-arylation of imidazole with aryl bromides under mild conditions. This simple method proceeds with excellent yield for the coupling of imidazole with various substituted aryl bromides demonstrating good tolerance of other functionalities.

Modification of chemical reactivity upon cyclodextrin encapsulation: : Asymmetric bromination of chalcone and benzylideneacetone

Abstract Asymmetric bromination of chalcone and benzylideneacetone ( trans -isomers) in crystalline β-cyclodextrin complex was studied. While bromination of chalcone in the absence of β-cyclodextrin yields erythro -dibromide, bromination of β-cyclodextrin-chalcone complex results in the formation of a mixture of erythro - and threo -dibromides respectively in the ratio 80:20. Complexation does not induce any variation in the bromination pattern in the case of trans -benzylideneacetone. These observations have been accounted for in terms of different conformations of the enones in the β-cyclodextrin-enone complexes. Complex formation between the substrate and cyclodextrin has been confirmed by various physical methods.

Per-6-amino-β-cyclodextrin as a reusable promoter and chiral host for enantioselective Henry reaction.

A highly efficient enantioselective Henry reaction has been carried out using per-6-ABCD as a supramolecular chiral host and promoter to give the corresponding adduct with high yield (up to 99%) and enantiomeric excess (up to 99%). Per-6-ABCD also promotes the diastereoselective Henry reaction in a syn-selective manner to give the adduct up to 99% yield with 99:1 syn/anti selectivity. The enantiomeric excess of the syn-adduct is 99%. The catalyst is recovered and reused without loss in its activity.

Melamine‐Based Microporous Network Polymer Supported Palladium Nanoparticles: A Stable and Efficient Catalyst for the Sonogashira Coupling Reaction in Water

A template consisting of a melamine‐based microporous polymer network was synthesized and utilized as a solid support to stabilize palladium nanoparticles; the resulting Pd/SNW1 material showed good catalytic activity in copper‐free Sonogashira coupling in water. Various aryl iodides were efficiently coupled with arylacetylenes under very low catalyst loadings in an environmentally benign medium. Hot filtration tests confirmed the heterogeneity of the catalyst, which was reused under the optimized conditions without any significant change in its activity. This simple preparation of the catalyst, the stability of the catalyst, product selectivity, and easy recovery and regeneration indicate the possible utilization of this catalytic system in a multitude of catalyzed reactions and industrial processes.

Copper(I)-Catalyzed Three Component Reaction of Sulfonyl Azide, Alkyne, and Nitrone Cycloaddition/Rearrangement Cascades: A Novel One-Step Synthesis of Imidazolidin-4-ones

A novel one-pot azide-alkyne/ketenimine-nitrone cycloaddition sequence that is induced by copper(I) and allows the transformation of sulfonyl azides, alkynes, and nitrones to highly substituted imidazolidin-4-ones is described. The corresponding heterogeneous version utilizing Cu(I)-modified zeolites as recyclable heterogeneous catalysts shows marginally improved yield and diastereoselectivity.

Per-6-amino-β-cyclodextrin as a Chiral Base Catalyst Promoting One-Pot Asymmetric Synthesis of 2-Aryl-2,3-dihydro-4-quinolones

A highly efficient one-pot synthesis of enantiomerically enriched 2-aryl-2,3-dihydroquinolin-4(1H)-ones has been carried out for the first time using per-6-ABCD as a supramolecular host, chiral base catalyst, and a reusable promoter to give the corresponding scaffold with high yield (up to 99%) and enantiomeric excess (up to 99%). The catalyst is recovered and reused without loss in its activity.

Zeolite-mediated regioselective nitration of phenol in solid state

Phenol (I) is nitrated regioselectively by fuming nitric acid inside the cages of faujasite zeolites. While nitration as hexane slurry in CsY and molecular sieve 5 A leads to predominant formation of para-nitrophenol (III), a remarkable ortho-selectivity is observed in solid state nitration to yield exclusively ortho-nitrophenol (II). Loading level of the substrate inside the supercage alters significantly the relative yield of the various products. Other advantage of this zeolite-mediated nitration include significant reduction in polynitration and absence of mixed nitrating agents.

K10 montmorillonite clays as environmentally benign catalysts for organic reactions

Montmorillonite is one of the most intensively explored catalytic materials in heterogeneous catalysis due to its low cost and eco-friendliness. Also, it possesses some unique properties like cation exchange capacity and swelling ability, thereby accommodating various guest species in its interlayers. In this Perspective, we describe the catalytic utility of K10-montmorillonite as solid acids and supports for complexes or metal nanoparticles in unimolecular as well as bimolecular reactions as reported mainly by our group. A very brief introduction is presented to highlight the structural properties of K10 clay and its merits in heterogeneous catalysis. The main part of this review is organized according to the role of clay in various organic reactions. An emphasis is given to highlighting the greenness of the processes, and a fair comparison is also provided between clay catalysts with respect to other homogeneous or heterogeneous catalysts. Finally, we summarize the current status and provide our views on future trends and developments.