Sunil P. Gupte

Oxidative carbonylation of aniline over Pd/C catalyst: effect of promoters, solvents, and reaction conditions

Oxidative carbonylation of aniline to N,N′-diphenylurea over 5% PdC NaI catalyst has been reported. The effects of promoters, solvents, reaction conditions, and pretreatment of catalyst with reactants have been investigated. Pretreatment of 5% PdC catalyst with O2, CO, and aniline resulted initially in a decrease in the activity of the catalyst. Activity-versus-NaI concentration and activity-versus-O2 pressure curves passed through maxima, indicating inhibition of rates at higher concentrations. CO pressure showed a linear dependence below 35 atm pressure, but zero-order behavior at higher pressures. The variation in activity was 1.6th order with respect to aniline concentration. Higher activity is obtained in polar solvents. Process parameters had a strong influence on the activity of the catalyst, but the selectivity for N,N′-diphenylurea was unaffected.

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.

Carbonylation of 2,4-dinitrotoluene using homogeneous Pd and Rh complex catalysts

Abstract The activity of Pd and Rh complex catalysts (Pd(py)2Cl2, Rh(py)3Cl3, etc.) in the carbonylation of 2,4-dinitrotoluene (DNT) has been investigated, and the effect of ligands, metal oxide and chloride promoters on the conversion of DNT and selectivity of isocyanates has been studied. It was found that these catalysts exhibit very high selectivity for total isocyanates. The intermediate isocyanates formed were characterized by GC-MS techniques. The effects of free pyridine on the activity of both Pd and Rh complex catalysts showed that an optimum ratio of py/metal exists for a given set of conditions. The influence of CO pressure, catalyst concentration, DNT concentration, temperature and contact time on the activity of the Pd(py)2Cl2 catalyst was also studied. It was observed that higher CO pressure and catalyst concentration with a shorter contact time are conditions which favour higher selectivity for 2,4-toluene diisocyanate.

Oxidative carbonylation of aniline over Pd-ZSM-5 catalyst

The oxidative carbonylation of aniline over Pd-ZSM-5 is reported. Pd-ZSM-5 catalyst is found to offer significant advantage with respect to CO2 formation. The average activity of Pd-ZSM-5 catalyst was found to be about 80 times higher compared to soluble metal complex catalysts.

Carbamate synthesis by solid-base catalyzed reaction of disubstituted ureas and carbonates

A simple and efficient methodology to prepare carbamates has been demonstrated for the first time from symmetrical ureas and organic carbonates in the presence of solid base catalysts.

Activity and selectivity of supported Rh complex catalyst in carbonylation of nitrobenzene

Abstract The activity and selectivity behaviour of Rh(py)3Cl3 and Rh(CO)Cl(PPh3)2 complex catalysts on various supports for carbonylation of nitrobenzene to methyl phenyl carbamate has been investigated. The best catalytic activity was shown by Rh(py)3Cl3 on γ-Al2O3 and Rh(CO)Cl(PPh3)2/ zeolites catalysts. The effect of temperature, CO pressure and initial concentration of nitrobenzene on conversion of nitrobenzene and selectivity to methyl phenyl carbamate was studied. The results have been compared with the corresponding homogeneous catalysts. Carbon monoxide interaction with supported Rh catalyst was investigated using in-situ FT-IR spectroscopy. A plausible mechanistic pathway for carbonylation of nitrobenzene has been proposed.

Highly Efficient Sulfimidation of 1,3‐Dithianes by Cu(I) Complexes

Abstract A series of four Cu(I) complexes were tested for sulfimidation of 1,3‐dithianes in the presence of [N‐(p‐tolysulfonyl)imino]phenyliodinane (PhI=NTs) as the nitrene‐transfer agent. Cu(TMPhen)(PPh3)Br is an efficient catalyst with more than 90% yield of the corresponding product with less reaction time as compared to the literature copper(I) complexes.

Carbonylation of benzyl chloride in a biphasic system using phase transfer catalysts

Carbonylation of benzyl chloride to phenyl acetic acid is of great importance, from synthesis as well as catalyst chemistry point of view. This paper presents a study of phase transfer catalysed carbonylation of benzyl chloride in a biphasic liquid mixture as reaction medium, under very mild conditions (14 atm & 338K). The role of different phase transfer catalysts in promoting the Pd complex catalysed reaction is found different. Quaternary ammonium halides were found to be better phase transfer agents for this reaction. Different organic solvents as the second liquid phase also played their own role in changing the activity of the catalyst and selectivity to phenyl acetic acid. An increase in the ligand concentration reduced the deactivation of the Pd complex catalyst to Pd metal thereby increasing the activity of the catalyst considerably.

Environmentally benign synthesis of β-hydroxy sulfides using cyclic carbonates catalyzed by large-pore zeolites

Abstract An efficient one-pot synthesis of β-hydroxy sulfides from thiophenol and cyclic carbonates catalyzed by large-pore zeolites has been reported. Reaction of thiophenol with ethylene carbonate in the presence of the Na-X zeolite catalyst gave the highest yield of 2-(phenylthio)ethanol (100%), while reaction with propylene carbonate a highest yield of regioselective product 1-(phenylthio)propan-2-ol was obtained (97%). Enantiomerically pure 1,2-propylene carbonate gave highly regioselective and stereospecific phenylthiopropanol, demonstrating that original chirality of propylene carbonate is retained. A plausible mechanism has been proposed for zeolite-catalyzed transformation involving a chemoselective nucleophilic attack of thiophenoloxide ion onto the less-substituted carbon of cyclic carbonate. The Na-X zeolite catalyst is recyclable and provides advantages of green chemistry approach to the synthesis of β-hydroxy sulfides without the use of any solvent.

Adsorption of formaldehyde and butynediol from aqueous solutions on a Cu2C2-silica gel catalyst

The effect of equilibrium concentration on adsorption has been studied at different temperatures and the nature of isotherms is discussed. For the formaldehyde-Cu2C2-silica gel system, Freundlich type equations describe the data satisfactorily.AbstractВлияние равновесной концентрации на адсорбцию было исследовано при различных температурах. Обсуждается природа изотерм. Для системы формальдегид-Cu2C2-силикагель уравнение типа Фрайндлиха удовлетворительно описывает результаты.