Ashutosh A. Kelkar

Copper-catalyzed amination of aryl halides: single-step synthesis of triarylamines

Abstract A simple and efficient methodology for the synthesis of triarylamines in a single step has been demonstrated using a ligand-free CuI catalyst and potassium tertiary butoxide as the base. Use of chelating ligands leads to the formation of triarylamine derivatives selectively (95% yield) with high catalytic activity.

Activity of homogeneous transition metal catalysts for oxidative carbonylation of aniline to N,N'diphenyl urea

Oxidative carbonylation of aniline to N,N′diphenyl urea was achieved at 100°C and atmospheric pressure conditions. The screening of several homogeneous transition metal complexes was carried out. The best catalytic activity was shown by [Ru(CO)3I3]NBu4 catalyst. The effect of solvents, temperature, aniline and promoter concentration etc. on the activity and selectivity of this catalyst was studied. The activation energy of the reaction is evaluated as 26.6 kcal/mol. A plausible mechanistic pathway for oxidative carbonylation of aniline to diphenyl urea has also been proposed.

Asymmetric Transfer Hydrogenation of Imines in Water by Varying the Ratio of Formic Acid to Triethylamine

Asymmetric transfer hydrogenation (ATH) of imines has been performed with variation in formic acid (F) and triethylamine (T) molar ratios in water. The F/T ratio is shown to affect both the reduction rate and enantioselectivity, with the optimum ratio being 1.1 in the ATH of imines with the Rh-(1S,2S)-TsDPEN catalyst. Use of methanol as a cosolvent enhanced reduction activity. A variety of imine substrates have been reduced, affording high yields (94-98%) and good to excellent enantioselectivities (89-98%). In comparison with the common azeotropic F-T system, the reduction with 1.1/1 F/T is faster.

Conversion of concentrated sugar solutions into 5-hydroxymethyl furfural and furfural using Brönsted acidic ionic liquids

Catalytic amounts of recyclable Bronsted acidic ionic liquids (BAILs) yielded HMF (73%) and furfural (81%) with high selectivity from highly concentrated solutions of D-fructose (40 wt%) and D-xylose (3 wt%), respectively. With a 6 wt% D-xylose solution, 73% yield was observed. An activity–property correlation of BAIL is established.

Role of cation–anion cooperation in the selective synthesis of glycidol from glycerol using DABCO–DMC ionic liquid as catalyst

Transesterification of dimethyl carbonate with glycerol has been investigated using 1,4-diazabicyclo [2.2.2] octane (DABCO) based ionic liquid as a catalyst. DABCO reacted with dimethyl carbonate to form ionic liquid as the reaction progressed. Though the basicity of DABCO based ionic liquid was lower than that of DABCO, the catalytic activity and selectivity to glycidol was higher with DABCO based ionic liquid as a catalyst, indicating that basicity may not be the only criterion in deciding activity and selectivity of the reaction. The cooperative effect of the cation and anion of the ionic liquid is responsible for the observed results. The best results (97% glycerol conversion with 83% selectivity to glycidol and 17% selectivity to glycerol carbonate) were obtained using DABCO based ionic liquid as a catalyst. A plausible mechanism involving the role of both the cation and anion of the ionic liquid has been proposed.

Efficient synthesis of glycerol carbonate/glycidol using 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) based ionic liquids as catalyst

Transesterification of dimethyl carbonate with glycerol to glycerol carbonate has been catalyzed efficiently using basic ionic liquids as catalysts. Activity of all the ILs tested is very high and the best result (96% conversion with 82% selectivity to glycerol carbonate and 18% selectivity to glycidol) was obtained using IL1 as catalyst. The effect of catalyst loading has significant influence on the selectivity pattern. The higher activity of the ionic liquid is explained with a plausible mechanism based on the co-operative effect of both cation and anion.

Asymmetric transfer hydrogenation of imines in water/methanol co-solvent system and mechanistic investigation by DFT study

Asymmetric transfer hydrogenation of various cyclic imines proceeded efficiently with water/methanol co-solvent media in 20 min with excellent yields and enantioselectivities by employing Rh–TsDPEN catalyst and sodium formate as a hydrogen donor. The role of the co-solvent in enhanced productivity of the reaction was investigated by DFT. The mechanism for ATH of the imines has been discussed on the basis of the DFT study.

Carbonylation of methanol to acetic acid using homogeneous Ru complex catalyst

Abstract Carbonylation of methanol to give acetic acid catalysed by Ru complexes such as trans-Ru(CO)2Cl2(PPh3)2, cis-Ru(CO)2Cl2(PPh3)2 and H2Ru(CO)(PPh3)3 is reported. The highest activity and selectivity were obtained with H2Ru(CO)(PPh3)3 as the catalyst precursor. Hydrogen increases the activity and selectivity of catalysts such as trans-Ru(CO)2Cl2(PPh3)2, cis-Ru(CO)2Cl2(PPh3)2, but has no influence on the activity and selectivity in the case of H2Ru(CO)(PPh3)3.

Carbonylation of ethanol using homogeneous Ir complex catalyst: effect of ligands and reaction conditions

Abstract Carbonylation of ethanol using IrCl 3 · 3H 2 O as catalyst precursor with HI as a promoter is reported. The role of N- and P-containing ligands and solvents, and the influence of reaction conditions on the activity and selectivity is discussed. The average activity vs. HI concentration showed an unusual trend with a maximum. The water-gas shift reaction was found to be significant above 483 K and at higher concentrations of HI (⪢1.12 × 10 −3 mol cm −3 ).

Carbonylation of methyl acetate to acetic anhydride using homogeneous nickel complex catalyst

Abstract Carbonylation of methyl acetate to acetic anhydride using nickel complex catalysts with iodide promoter and an organic N- or P-containing base as a ligand is reported. The effect of different types of ligands and reaction conditions on activity of the catalyst was investigated. The highest catalytic activity was observed with isoquinoline as a ligand. The activity of the catalyst was found to be enhanced significantly in the presence of hydrogen, while retaining its high selectivity to acetic anhydride. The activity decreased with increase in acetic anhydride concentration. The selectivity of acetic anhydride was found to be greater than 95–96% in the range of conditions studied.