Ashif H. Tamboli

Synthesis, characterization, and application of silica supported ionic liquid as catalyst for reductive amination of cyclohexanone with formic acid and triethyl amine as hydrogen source

A silica supported ionic liquid was synthesized and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, X-ray diffraction, N2 adsorption-desorption, and thermogravimetric analysis. All these techniques, especially SEM results indicated the presence of well-defined spherical particles having diameters larger than the pristine silica particles, confirming the successful immobilization of the ionic liquid. The prepared silica supported ionic liquid was used in the reductive amination of cyclohexanone under different conditions with different azeotropic mixtures of formic acid and triethyl amine as a hydrogen source. The catalyst showed efficient catalytic performance and excellent yields of N-cyclohexyl amine derivatives in the range of 58% to 84% at 30 °C. After completion of the reaction, the catalyst was easily recovered by simple filtration and reused for another five cycles without any significant impact on product yields. The obtained catalytic performance indicates that the present catalyst is green, very active, and reusable for the reductive amination of cyclohexanone.

Efficient fixation and conversion of CO2 into dimethyl carbonate catalyzed by an imidazolium containing tri-cationic ionic liquid/super base system

The synthesis route used to prepare dimethyl carbonate from CO2 and methanol is a most attractive route from a green chemistry point of view. Herein, we systematically studied binary catalyst systems for the synthesis of dimethyl carbonate from CO2 and methanol. It was found that [GLY(mim)3][NTf2]3IL/DBU, [GLY(mim)3][NTf2]3/MTBD and [GLY(mim)3][NTf2]3/TBD are effective binary catalysts for the direct synthesis of DMC without the need of a dehydration system. In particular, the [GLY(mim)3][NTf2]3 IL/1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) system was found to have 37% MeOH conversion and 93% DMC selectivity under mild reaction conditions. However, the tri-imidazolium salts were compatible with DBU for effective CO2 adsorption, possibly because of the reactive C(2)–H in the imidazolium ring. Furthermore, the [GLY(mim)3][NTf2]3 IL/DBU catalytic system could be easily recovered and reused three times without any obvious loss of catalytic activity. The catalytic reactivity of [GLY(mim)3][NTf2]3 IL/DBU for the synthesis of DMC was proved by its predictable mechanism on the basis of 13C NMR spectroscopy.