Krishna M. Deshmukh

Efficient synthesis of cyclic carbonate from carbon dioxide using polymer anchored diol functionalized ionic liquids as a highly active heterogeneous catalyst

A highly efficient catalytic protocol using polymer supported diol functionalized ionic liquids (PS-DFILX) was developed for cyclic carbonates synthesis from carbon dioxide and epoxide providing remarkable yields of desired products under solvent free conditions. The developed methodology was found to be applicable for a wide variety of epoxides producing the corresponding cyclic carbonate in good to excellent yields. Besides this, the catalyst could be reused for five consecutive recycles without any significant loss in its catalytic activity. The hydroxyl groups present on the vicinal carbon of the catalyst seems to be vital for efficiency of the catalyst endowing high activity, stability and recyclability. The present protocol thus offers appreciable advantages with respect to excellent yield, short reaction time, operational simplicity and environmentally benign characteristics.

Applications of ionic liquids in organic synthesis and catalysis

In recent years, various novel and greener methodologies have been developed using ionic liquids (ILs). In these reactions, IL has played multiple roles like catalyst, solvent, and catalyst support. In some cases, it was observed that IL enables efficient catalytic reactions in comparison with conventional molecular solvents. On the other hand, although a number of catalytic reaction processes in which ILs are used have been established in industry, there were also some unexpected problems, such as unintelligible aberrance or degradation of so-called task-specific ILs occurring in reaction processes and on the pilot plant scale. Also, several urgent questions regarding the fundamental aspects of ILs particularly toxicity and greener preparation methods need to be clarified. Several industrial applications of ILs are also discussed.

Improved activity and stability of Rhizopus oryzae lipase via immobilization for citronellol ester synthesis in supercritical carbon dioxide.

In present work, Rhizopus oryzae lipase immobilized on a film prepared using blend of hydroxylpropyl methyl cellulose (HPMC) and polyvinyl alcohol (PVA) was investigated for synthesis of citronellol esters with supercritical carbon dioxide (Sc-CO(2)) as a reaction medium. The transesterification reaction was optimized for various reaction parameters like effect of molar ratio, acyl donor, time, temperature, enzyme concentration, effect of pressure and co-solvent to achieve the maximum yield of desired product. The results obtained signify remarkable increment (about eightfold) in the yield of citronellol acetate (91%) as compared to that of free lipase (11%) in Sc-CO(2). The developed biocatalytic methodology provides a substantial advantage of low biocatalyst loading (1.5%, w/v), lower reaction temperature (45°C) and lower pressure (8 MPa) as compared to previous reports. The immobilization method has significantly enhanced the operational stability of lipase for ester synthesis under Sc-CO(2) conditions. The developed methodology was successfully applied for synthesis of three different industrially important citronellol esters namely citronellol acetate (91%), citronellol butyrate (98%), citronellol laurate (99%) with excellent yields using vinyl esters as acyl donor under Sc-CO(2) conditions. In addition, the immobilized biocatalyst was effectively recycled for three consecutive recycles.

One-pot electrochemical synthesis of palladium nanoparticles and their application in the Suzuki reaction

A novel potential controllable, template free, electrodeposition/synthesis of palladium nanoparticles on an electrode surface as well as in the bulk electrolyte using ionic liquid as an electrolyte cum stabilizer is reported for the first time. The present method of preparation of palladium nanoparticles is advantageous as it eliminates the requirement of additional stabilizers or capping agents. The prepared palladium nanoparticles are characterized by different techniques such as TEM, SEM, EDAX and XPS analyses. These nanoparticles exhibited high catalytic activity for the Suzuki coupling reaction of unactivated halides in aqueous media with high TON.

Brønsted acidic ionic liquid: a simple, efficient and recyclable catalyst for regioselective alkylation of phenols and anti-Markovnikov addition of thiols to alkenes

A highly efficient protocol for the alkylation of phenols and anti-Markovnikov addition of thiols with various alkenes has been developed using a Bronsted acidic ionic liquid, N-methyl-2-pyrrolidone hydrogen sulfate [NMP]+HSO4−, under solvent free conditions. The developed methodology offers appreciable advantages with respect to excellent yield, short reaction time and high regioselectivity. The C–C and C–S bond formation has been achieved under metal free conditions.

Ionic Liquid : An Efficient and Recyclable Catalyst for the Synthesis of 1-Amidoalkyl-2-naphthols and 1-Carbamatoalkyl-2-naphthols Under Solvent-Free Conditions

Abstract A simple and efficient protocol for the one-pot synthesis of 1-amidoalkyl-2-naphthols and novel 1-carbamatoalkyl-2-naphthols has been described under solvent-free conditions, using N-methyl-2-pyrrolidone hydrogen sulfate as a reusable Brønsted acidic ionic liquid. This methodology has several advantages such as use of a halogen-free ionic liquid , excellent yields, short reaction time, easy workup procedure, and reusable catalyst. GRAPHICAL ABSTRACT

Polyvinylsulfonic acid as a novel Brønsted acid catalyst for the synthesis of bis(indolyl)methanes

Abstract Polyvinylsulfonic acid as a novel, biodegradable, and efficient Brønsted acid catalyst for the reaction of indoles with aldehydes to obtain bis(indolyl)methanes has been reported. The catalyst exhibited remarkable activity, recyclability, and tolerated a wide variety of functional groups providing the desired bis(indolyl)methanes in excellent yield (64–96%) at room temperature using ethanol as a solvent. The effect of different reaction parameters like solvent, temperature, catalyst doses, and recyclability were investigated for the title reaction.

Ultrasound assisted regioselective sulfonation of aromatic compounds with sulfuric acid

A simple and convenient methodology for selective sulfonation of aromatic compounds using sulfuric acid under sonication is described. The present methodology shows a considerable enhancement in the reaction rate along with improved selectivity compared with the reactions performed under silent conditions. The effect of various parameters such as agitation speed, sulfuric acid concentration, and temperature on reaction system have been investigated and are explained on the basis of ultrasonically generated cavitational effects.