Synthesis Of Methyl Carbamate Research Articles

고압반응 하에서 요소와 메탄올을 사용한 메틸카바메이트와 디메틸카보네이트 제조에 관한 금속산화물 촉매 및 이온성액체의 영향

고압 반응시스템에서 요소와 메탄올로부터 메틸카바메이트(MC) 및 디메틸카보네이트(DMC)의 제조에 관한 금속산화물촉매와 이온성액체의 영향을 고찰하였다. 고립계에서 요소와 메탄올로부터 MC 수율은 촉매를 사용하지 않고도 <TEX>$150^{\circ}C$</TEX> 이상의 반응온도에서 거의 100%를 나타내었으나, DMC 수율은 반응온도와 무관하게 1.5% 이하로 매우 낮은값을 나타내었다. 또한 MC와 메탄올로부터 DMC 수율은 <TEX>$ZnCl_{2}$</TEX> 촉매를 사용한 경우에 가장 우수하였으며, 최적조건에서 16.3% 정도를 나타내었다. DMC 수율은 반연속식 실험에서 나노 크기의 촉매와 이온성액체를 함께 적용한 경우에 좀 더 향상되었다. Effect of metal oxide catalysts and ionic liquids on the synthesis of methyl carbamate(MC) and dimethyl carbonate (DMC) from urea and methanol was investigated in a high pressure reaction system. In closed system, MC yield from urea and methanol reached almost 100% at reaction temperature over <TEX>$150^{\circ}C$</TEX> without catalyst, whereas DMC yield of 1.5% under was obtained irrespective of catalysts used. In DMC synthesis from MC and methanol, <TEX>$ZnCl_{2}$</TEX> showed the highest catalytic activity and led to the DMC yield of 16.3% under optimal conditions. Furthermore, DMC yield can be enhanced by the simultaneous application of ionic liquids with nano-sized catalysts in semi-continuous reaction system.

Reactions of Dimethyl Carbonate with Aliphatic Amines Under High Pressure

A facile synthesis of methyl carbamates from primary amines and dimethyl carbonate has been achieved at room temperature using high pressure. High-pressure synthesis of methyl carbamates described herein provides access to the target molecules in an efficient and environmentally friendly way without solvent or catalyst. Better conversion and selectivity than previously published procedures were obtained.

Synthesis of Methyl Carbamates from Primary Aliphatic Amines and Dimethyl Carbonate in Supercritical CO2: Effects of Pressure and Cosolvents and Chemoselectivity

[reaction: see text] At 130 degrees C, in the presence of CO2 (5-200 bar), primary aliphatic amines react with dimethyl carbonate (MeOCO2Me, DMC) to yield methyl carbamates (RNHCO2Me) and N-methylation side-products (RNHMe and RNMe2). The pressure of CO2 largely influences both the reaction conversion and the selectivity toward urethanes: in general, conversion goes through a maximum (70-80%) in the midrange (40 bar) and drops at lower and higher pressures, whereas selectivity is continuously improved (from 50% up to 90%) by an increase of the pressure. This is explained by the multiple role of CO2 in (i) the acid/base equilibrium with aliphatic amines, (ii) the reactivity/solubility of RNHCO2- nucleophiles with/in DMC, and (iii) the inhibition of competitive N-methylation reaction of the substrates. Cosolvents also affect the reaction: in particular, a drop in selectivity is observed with polar protic media (i.e., MeOH), plausibly because of solvation effects (through H-bonds) of RNHCO2- moieties. The reaction shows also a good chemoselectivity: bifunctional aliphatic amines bearing either aromatic NH2 or OH substituents [XC6H4(CH2)n NH2, X = NH2, OH; n = 1, 2], undergo methoxycarbonylation reactions exclusively at aliphatic amino groups and give the corresponding methyl carbamates [XC6H4(CH2)n NHCO2Me] in 39-65% isolated yields.

Mechanistic studies on the role of carbon dioxide in the synthesis of methylcarbamates from amines and dimethylcarbonate in the Presence of CO 2.

N-alkylmethylcarbamates have been synthesized from amines and dimethylcarbonate (DMC) in the presence of carbon dioxide. The catatylic rote of CO 2 in the overall process has been investigated and elucidated.

Synthesis of alkyl carbamates in the presence of an aluminosilicate catalyst

1. A process was developed for obtaining alkyl carbametes from urea and the corresponding alcohols in the presence of an aluminosilicate catalyst. 2. Optimal regions for synthesis of methyl carbamate were determined by the Box-Wilson method of multifactor systematization. 3. The effect of various factors (temperature and length of reaction, ratio of initial reagents, space velocity of raw-material introduction, quality of the initial raw material, and length of operation of the catalyst) on the yield of methyl carbamate were studied. 4. C2-C5 alkyl carbamates were obtained in yields of 75–79% of the theoretical under the optimal conditions found for methyl carbamate.

Synthesis of alkyl carbamates?selective solvents for aromatic hydrocarbons

1. The synthesis of alkyl carbamates (C1-C5) has been conducted in the presence of KU-2 ion-exchange resin, in an autoclave and in a laboratory semi-continuous action assembly. 2. Optimum conditions for the synthesis of methyl carbamate or KU-2 catalyst have been selected: temperature, 140°; molar ratio, methanol to urea, 9∶1; reaction time, 15 min. 3. It has been shown that the catalyst operates for a period of 200 h without reducing the yield of methyl carbamate.