Kishor P. Dhake

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.

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.

PS-Pd–NHC: an efficient and heterogeneous recyclable catalyst for direct reductive amination of carbonyl compounds with primary/secondary amines in aqueous medium

A highly efficient polymer supported palladium-N–heterocyclic carbene (PS-Pd–NHC) catalytic system has been developed for direct reductive amination (DRA) of carbonyl compounds with primary/secondary amines in aqueous reaction medium. This new catalytic system represents a heterogeneous, recyclable and environmentally benign protocol. The developed methodology describes a simple one step approach for the synthesis of a wide variety of substituted amines exhibiting remarkable activity with excellent yield of a desired product. Furthermore, the catalyst was effectively recycled for six consecutive cycles without any significant loss in its catalytic activity.

An efficient and heterogeneous recyclable palladium catalyst for chemoselective conjugate reduction of α,β-unsaturated carbonyls in aqueous medium

An highly efficient PS-Pd-NHC catalytic system has been developed for chemoselective conjugate reduction of α,β-unsaturated carbonyl compounds providing good to excellent conversion with remarkable chemoselectivity (up to 100%). The developed protocol is more advantageous due to use of HCOONa as hydrogen source, environmentally benign water as solvent and effective catalyst recyclability.

An efficient, catalyst- and solvent-free N-formylation of aromatic and aliphatic amines

Abstract A simple, efficient, and cost-effective procedure for the synthesis of formamides under catalyst- and solvent-free conditions at 60°C using formic acid/ethyl formate as a formylating agent has been developed. The protocol is applicable to a wide variety of aromatic and aliphatic amines providing moderate to excellent yield of desired products.

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.

Direct allylic amination of allylic alcohols with aromatic/aliphatic amines using Pd/TPPTS as an aqueous phase recyclable catalyst

Direct activation of C–O bonds in cinnamyl/allyl alcohols with aromatic/aliphatic amines in aqueous medium using a water soluble Pd(OAc)2/TPPTS catalyst has been reported. The catalyst is highly efficient, chemoselective, simple, atom economical, greener and reusable up to eight consecutive cycles without aid of any co-catalyst. The protocol is applicable to a wide range of hindered and functionalized aromatic/aliphatic amines with excellent yield of the corresponding allyl amines.

Immobilization of steapsin lipase on macroporous immobead-350 for biodiesel production in solvent free system

Commercially available steapsin lipase was immobilized on macroporous polymer beads (IB-350) and further investigated for biodiesel production under solvent free conditions. The fatty acid methyl ester (biodiesel) synthesis was carried out by the methanolysis of fresh and used cooking sunflower oil. The enzymatic reaction for biodiesel synthesis was optimized with various reaction parameters and the obtained reaction conditions were 1: 6 molar ratio (oil: methanol), 50 mg biocatalyst and 20% water content at 45°C for 48 h under solvent free conditions. It was observed that 94% of biodiesel was produced under the optimized reaction conditions. The four step addition of methanol at the interval of 12 h was found to be more effective. Moreover the biocatalyst was effectively reused for four consecutive recycles and was appreciably stable for 90 days. The results obtained highlight potential of immobilized steapsin lipase for biodiesel production.

Pd(OAc)2-Catalyzed Carbonylative Coupling of Aryl Iodide with Ortho-Haloamines in Water

Abstract The carbonylative cross coupling of aryl iodide with ortho-haloaniline to ortho-haloanilide using phosphine-free Pd(OAc)2 catalyst in water as a reaction medium has been studied. The present protocol facilitated the reaction of o-haloanilines with a wide variety of hindered and functionalized aryl iodides, affording good yields of the desired products. The protocol was also extended for the synthesis of benzoxazoles through cyclization of ortho-haloanilide using Cu(acac)2 catalyst. GRAPHICAL ABSTRACT