Carbonic by transesterification

Synthesis of dimethyl carbonate by transesterification of ethylene carbonate and methanol using quaternary ammonium salt catalysts... 

Aromatic polycarbonates are currently manufactured either by the interfacial polycondensation of the sodium salt of diphenols such as bisphenol A with phosgene (Reaction 1, Scheme 22) or by transesterification of diphenyl carbonate (DPC) with diphenols in the presence of homogeneous catalysts (Reaction 2, Scheme 22). DPC is made by the oxidative carbonylation of dimethyl carbonate. If DPC can be made from cyclic carbonates by transesterification with solid catalysts, then an environmentally friendlier route to polycarbonates using C02 (instead of COCl2/CO) can be established. Transesterifications are catalyzed by a variety of materials K2C03, KOH, Mg-containing smectites, and oxides supported on silica (250). Recently, Ma et al. (251) reported the transesterification of dimethyl oxalate with phenol catalyzed by Sn-TS-1 samples calcined at various temperatures. The activity was related to the weak Lewis acidity of Sn-TS-1 (251). 

Preparation of a Polycarbonate from 4,4-lsopropylidenediphenol (Bisphenol A) and Diphenyl Carbonate by Transesterification in the Melt... 

Wei T, Wang M, Wei W et al (2003) Synthesis of dimethyl carbonate by transesterification over CaO/carbon composites. Green Chem 5(3) 343-346... 

SCHEME 6.9 Synthesis of dimethyl carbonate and diphenyl carbonate by transesterification. 

Z Dong. Synthesis of propylene carbonate by transesterification. Hangzhou Chemical Engineering, (3) 39-96,1979. 

The synthesis of six-membered cyclic carbonates by transesterification of propane-1,3-diols (PPDs) with diethyl carbonate catalyzed with sodium ethanolate described by Carothers and Van Natta gives a yield of 40%. Also Pohoryles and... 

Feng X, Wang Q, Wang G, Qiu F. Preparation of Nano-TiOj by ethanol-thermal method and its catalytic performance for synthesis of dibutyl carbonate by transesterification. Chin J Catal 2006 27(3) 195-196. 

Zhou, W. Zhao, X. Wang, Y Zhang, J. Synthesis of Diphenyl Carbonate by Transesterification over Lead and Zinc Double Oxide Catalyst. Appl. Catal. A. Gen. 2004, 260,19-24. 

Some esters of substituted alcohols have been synthesized by transesterification. Treatment of 4-methyl-5-thiazolecarboxylic acid (14) with 3-chloroethyldiethylamine in acetone in the presence of anhydrous potassium carbonate gives the desired ester (15) in good vield (60%) (Scheme 10) (163). 

Cychc carbonates result from polyols by transesterification using organic carbonates (115). Thus sorbitol and diphenylcarbonate in the presence of dibutyl tin oxide at 140—150°C form sorbitol tricarbonate in quantitative yield (116). 

Linalool can be converted to geranyl acetone (63) by the CarroU reaction (34). By transesterification with ethyl acetoacetate, the intermediate ester thermally rearranges with loss of carbon dioxide. Linalool can also be converted to geranyl acetone by reaction with methyl isopropenyl ether. The linalyl isopropenyl ether rearranges to give the geranyl acetone. 

Yun-Jin Fang and Wen-De Xiao, Experimental and modeling studies on a homogeneous reactive distillation system for dimethyl carbonate synthesis by transesterification, Separation and purification technology, 34 (2004) 255. 

Cyclic carbonate esters are easily prepared from 1,2- and 1,3-diols. These are commonly prepared by reaction with A.A -carbonyldiimidazole214 or by transesterification with diethyl carbonate. 

Another example where PEG played the role of polymeric support, solvent, and PTC was presented by the group of Lamaty [72]. In this study, a Schiff base-proteded glycine was reacted with various electrophiles (RX) under microwave irradiation. No additional solvent was necessary to perform these reactions and the best results were obtained using cesium carbonate as an inorganic base (Scheme 7.64). After alkylation, the corresponding aminoesters were released from the polymer support by transesterification employing methanol in the presence of triethylamine. 

Komura, H., Yoshino, T. and Ishido, Y., Synthetic studies by the use of carbonates. II. Easy method of preparing cyclic carbonates of polyhydroxy compounds by transesterification with ethylene carbonate. Bull. Chem. Soc., 1973, 46, 550-553. 

Chapter VII.3). The conversion of VII/31to VII/32 (Scheme VII/8) however, goes in very good yield. Compound VII/33 is formed by transesterification [17]. One, two, and three carbon atom expansions, following the same reaction principle, have been published quite recently [19] [19a], By this method, ethyl l-methoxycarbonylmethyl-2-oxocyclohexancarboxylate, for example, can be transformed to ethyl 2-methoxycarbonyl-3-oxocycloheptancarboxylate in the presence of 1.2 equivalents of potassium tertiary butoxide in dimethylsulfoxide (41% yield). 

The formula for the stanoxane catalyst is (ClSi(CH3)20)2Sn-Sn(CH3)2Cl. Hyperbranched polycarbonates, (1), with only marginal crosslinking side reactions were prepared by Bruchmann [1] by transesterification, using diethyl carbonate and trihydroxy methylmethane catalyzed by potassium carbonate. 

Transesterifications of aliphatic carbonate esters with glycols are catalysed by alkali metal alkoxides. No catalyst is needed for the transesterification of diaryl carbonates with aliphatic diols. Alkyl carbonate esters and p-xylylene glycol undergo transesterification reactions when certain titanium compounds are used as catalysts. The preparation of aromatic polycarbonates by transesterification is best... 

The synthesis of aliphatic poly(carbonate-co-ester)s with about 1 1 molar ratio of the ester-to-carbonate repeat units was reported by CALB-catalyzed transesterification among diethyl carbonate, a diester, and a diol. Molecular weight Mw values reached 59000 at a reaction temperature of 90 °C. A carbonate-ester transesterification reaction between poly(butylene carbonate) and poly(butylene succinate) was also catalyzed by CALB at 95 °C to result in a block copolymer [57]. 

Thus, glycerol, the most important starter for the synthesis of polyether polyols for flexible PU foams and for polyether for rigid foams is produced by the hydrolysis of natural triglycerides (esters of glycerol with fatty acids with C6 to C22 carbon atoms), from vegetable or animal resources (reaction 17.1) [1]. Large quantities of glycerol appear in bio-diesel production, by transesterification of natural oils with methanol. 

Similar results are obtained in the transesterification of diethyl carbonate by 1-phenylethanol (Table 2). 

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