Dimethyl carbonate , hydrogenation methanol

Recently, density functional computation on hydrogenation of dimethyl carbonate to methanol, catalysed by Ru(II)-PNN catalyst 2 supported a stepwise hydrogenation mechanism (Fig. 13) [83, 84]. A hydride/methoxide metathesis-based mechanism was suggested by DFT [85]. 

However, the methyl cation (in itself a very energetic, unprobable species in the condensed state) is not expected to attack a carbon-hydrogen bond in dimethyl ether (or methanol) in preference to the oxygen atom. The more probable attack on oxygen would lead to the trimethyloxonium ion, which was observed experimentally447,463 On the action of a basic site the trimethyloxonium ion can then be deprotonated to form dimethyloxonium methylide ... 

In the case of experiments performed under the conditions of run 6, but in the presence of 1 ml of methanol, 1.6 equivalent of dimethyl carbonate was obtained according to GC analysis. No dimethyl carbonate was observed in the absence of hydrogen chloride. Therefore, in the early stage of the carbonylation of 3, Pd/C is partly oxidized to palladium chloride (eqn. 2). This compound reacts in turn with CO and MeOH to give, according to one of the routes described in Scheme 2, dimethyl carbonate and a zerovalent palladium complex (noted [Pd]). 

Schmidt and Wernicke74 have described a synthesis of digitalose starting with D-fucose dibenzyl mercaptal, which on condensation with acetone yielded the 4,5-isopropylidene derivative (LXXIV). Elimination of the dibenzyl mercaptal residues with mercuric chloride and cadmium carbonate in methanol gave 4,5-isopropylidene-D-fucose dimethylacetal (LXXV), from which the 2-benzyl ether was obtained on treatment with sodium and benzyl chloride. Methylation produced 2-benzyl-3-methyl-4,5-iso-propylidene-D-fucose dimethyl acetal (LXXVI), from which the iso-propylidene group was eliminated on treatment with methanolic hydrogen chloride, which also effected glycopyranoside formation (LXXVII). The... 

In Stork s synthesis (148), 5 - methyl - 6 - methoxy - 1 - tetralone (CLXXXIV) was converted into the tricyclic intermediate CLXX XVII in several steps involving condensation with dimethyl carbonate, addition of methyl isopropenylketone, and cyclization to the a, -unsaturated ketone CLXXXVI, followed by catalytic hydrogenation, replacement of the hydroxyl group in the resulting dihydro alcohol by a chlorine atom on treatment with phosphorus oxychloride in pyridine solution, and elimination of hydrogen chloride by methanolic sodium methoxide. 

The reaction of methanol, carbon monoxide and oxygen ( oxycarbony-lation ) with soluble palladium and copper salts gives dimethyl carbonate and/or dimethyl oxalate (dimethyl ethanedioate), for hydrogenation to ethylene glycol. Postulated mechanisms include the sequence... 

Daicel Chemical Industries, Ltd., has patented a process for reacting diamines, such as isophorone diamine (IPDA), with dimethyl carbonate. The condensation is accomplished in the presence of an alkaline catalyst, such as methanolic sodium methylate at 70 °C, to produce the diurethane. Treatment of the diurethane with hydrogenated terphenyl containing manganese acetate at 230 °C in vacuo produces isophorone diisocyanate by thermal decomposition. This non-phosgene process has a reported product yield of 93% of IPDI containing 1% isophorone monoisocyanate. 

N-Ethylpiperidine salt of 2-hydroxy-4,6-bistrichloromethyl-s-triazine hydrogenated with 2%-Pd-on-carbon in methanol containing 6 moles of triethyl-amine 2-hydroxy-4,6-dimethyl-s-triazine. Y 84%. Also from the triethylamine salt s. E. Kober, J. Org. Ghem. 25, 1728 (1960). 

As the radiation dose increases, melt temperature and density decrease. Discoloration also occurs. During irradiation, carbon dioxide, methane, hydrogen, methanol, and dimethyl ether are eliminated [32]. Because these low-molecular compounds are diffusing, a weight loss of 0.5% is expected with a dose of 200 kGy [737]. 

Dimethyl carbonate was quantitatively hydrogenated into methanol under mild, neutral conditions, catalysed by the Ru(II)-pincer complexes 2-3 and 6 under low hydrogen pressure and relatively low temperature with high TON (up to 4,400 after 14 h). Moreover, the hydrogenation of dimethyl carbonate proceeds smoothly under solvent free conditions in case of catalyst 2 and TON more than 990 were achieved after 8 h. 

Miscellaneous substances including carbonyl sulfide, diethyl ether, dimethyl carbonate, dimethyl ether, ethanol, heavy water, hydrogen chloride, hydrogen sulfide, methanol, methyl chloride, nitrous oxide, Novec-649, sulfur hexafluoride, sulfur dioxide, and trifluoroiodomethane. 

Research of the carbonylation of methanol to other products, such as methyl formate [284] and dimethyl carbonate [285], is also imderway. Should an additional source of hydrogen be available, the possibility of using CO to increase the yield of methanol through the intermediate formation of methyl formate, proposed by Christiansen as long ago as 1919 [286], can also be considered ... 

On the basis of DFT study of hydrogenation of dimethyl carbonate catalysed by a PNN-ligated ruthenium complex, a direct metal hydride and ligand proton transfer mechanism with three cascade catalytic cycles for the hydrogenation of dimethyl carbonate, methyl formate, and formaldehyde to methanol has been proposed. ... 

In the first step, a CO2 molecule diffuses towards the indium electrode, and gets adsorbed on its surface, where it is activated and the C02 radical anion forms (Equation 1.20). As C02 ion pairs with BMIM+, which reacts with methanol to form CHs-O-COO , where the unpaired electron is located on the oxygen atom that originates from methanol (Equation 1.21). Next, molecular hydrogen is released (Equation 1.22), and dimethyl carbonate is formed in a subsequent chemical reaction with methyl iodide (Equation 1.23). This procedure enabled the synthesis of dimethyl carbonate at reasonable Faradaic yields of 73.2-76%, at potentials from -1.7 to -1.9 V (vs. Ag) [68,147]. 

Substances 2,6-Dibromoquinone-4-chloroimide Sodium hydrogen carbonate Dimethyl sulfoxide (DMSO) Chloroform Methanol Ethanol... 

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