Cyclic Carbonic Esters

Easily prepared from the appropriate monosaccharide, a glycal is an unsatu-rated sugar with a C1-C2 double bond. To ready it for use in potysaccharide synthesis, the primary -OH group of the glycal is first protected at its primary -OH group by formation of a silvl ether (Section 17.8) and at its two adjacent secondary - OH groups by formation of a cyclic carbonate ester. Then, the protected glycal is epoxidized. 

The thietanes are most often prepared through ring closure of 1,3-dibromides or 1,3-disulfonate esters1930 239,240, through fusion of cyclic carbonate esters of 1,3-diols with... 

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. 

Cyclic carbonic esters can be readily obtained from 1,2-diols and CDI.[242H254] Apart from the observed high yields, the procedure is so straightforward that it undoubtedly constitutes the method of choice for compounds of this type. The procedure offers the advantages of mildness, simplicity, and absence of by-products other than imidazole,... 

The best procedure for obtaining a cyclic carbonic ester requires that CDI (4 equiv.) be added gradually over a period of ca. eight hours during refluxing of the reaction mixture. However, it was found in the case of cw-cyclohexane diol that if the diol and CDI are dissolved together in benzene and the solution heated under reflux, the bis(imidazole-iV-carboxylate) is obtained instead of the cyclic carbonic ester. 4 ... 

Table 3-13. Cyclic carbonic esters obtained by the reaction of 1,2-diols with CDI.

Cyclic carbonic esters were also prepared, for example, from the cardiac glycoside proscillaridine[257] (where besides CDI the benzyloxycarbonylimidazole was successfully used), ingenol, 2581 the macrolide antibiotic tylosine,[259] and an erythromycin A derivative.12601... 

S. Billecke, D. Draganov, R. Councell, P. Stetson, C. Watson, C. Hsu, B. N. La Du, Human Serum Paraoxonase (PON1) Isozymes Q and R Hydrolyze Lactones and Cyclic Carbonate Esters , Drug Metab. Dispos. 2000, 28, 1335- 1347. 

Polymerization of a cyclic carbonate ester yields a linear polycarbonate [Kuhling et al., 1989 Rokicki, 2000], For example, the cyclic oligomer (m — 2-20 in Eq. 7-85) of the... 

A rapid one-pot method for converting 1,3-diols into oxetanes by the intramolecular Williamson reaction has recently been described. The monolithium salt is generated by treatment of the diol with one equivalent of butyllithium in cold THF, followed by addition of one equivalent of tosyl chloride to give a monotosylate, which is cyclized by addition of a second equivalent of butyllithium (equation 83). Yields of 70-90% are reported for a variety of alkyl- and aryl-substituted oxetanes (81S550). Another simple method for converting 1,3-diols into oxetanes consists of converting them to cyclic carbonate esters by ester... 

Carbon dioxide. The patent literature contains a number of disclosures describing addition of carbon dioxide to ethylene or propylene oxide for the preparation of cyclic carbonate esters,81 -, 030 uu, um... 

SYNTHESIS To a well-stirred solution of 120 g thiourea in 800 mL 2N HCL, there was added a solution of 100 g benzoquinone in 500 mL acetic acid over the course of 15 min. Stirring was continued for an additional 0.5 h at room temperature, and then the reaction mixture was heated on the steam bath for 1 h. With cooling in ice water, a heavy crop of crystals separated. These were removed by filtration and air dried to provide 90.1 g of 5-hydroxy-l,3-benzoxathiol-2-one (2-mercaptohydro-quinone cyclic carbonate ester) with a melting point of 170.5-172.5 °C. 

Carbamate esters to protect alcohols, 62 to protect amines, 104, 387-388 to protect phenols, 167 Carbonate esters to protect alcohols, 104 to protect phenols, 165-167 Carbonates, cyclic, see Cyclic carbonate esters... 

Nemirowsky, in 1883, reported the preparation of the cyclic carbonate ester I from ethylene glycol and phosgene, and, in 1909, Siegfried and... 

Billecke, S., Draganov, D., Counsell, R., Stetson, P., Watson, C., Hsu, C., La Du, B.N. (2000). Human serum paraoxonase (PONl) isozymes Q and R hydrolyze lactones and cyclic carbonate esters. Drug Metab. Dispos. 28 1335-42. 

Mixed esters of oxalate containing one benzylic substituent are reduced in good yield using in situ trans-esterification to the corresponding hydrocarbon and oxalate half-ester [72]. Esters of vicinal diols (including cyclic carbonate esters) [73] and -halo esters [74] are often reduced to the corresponding olefin [72,75]. 

In 1978, a patent was published by the AGROFERM AG claiming that cyclic carbonic esters such as ethylene carbonate and 1,2-propylene carbonate are particularly suitable solvents for PHB, especially for the extraction of PHA from moist microbial biomass. Here, PHA-rich biomass is suspended in the cyclic ester and heated under stirring. After removal of the hot extract, PHA is precipitated from the liquid by simple cooling down or addition of small amounts of water. As a drawback it turned out that the extraction with both cyclic esters, but especially with ethylene carbonate, results in a high degree of depolymerization, hence in inferior molecular masses. This effect is very dependent on temperature and time of the extraction [80]. 

Cyclic carbonate esters are easily prepared from uic-diols and can be used in a complementary fashion to the cyclic acetals previously described. These esters are commonly prepared from N,N -carbonyldiimidazole or by transesterification using diethyl carbonate. These reagents are preferable to phosgene both in efficiency and convenience. 

The electrolyte for LIBs is a mixture of organic solvents and an electrolyte salt compoimd. The common solvents are a mixture of cyclic carbonate esters, such as ethylene carbonate and propylene carbonate, and linear carbonate esters, such as dimethyl carbonate and diethyl carbonate. The solution is completed with the addition of a salt compound such as LiPFe or LiBp4. Electrolyte solutions must enable the Li ions to transport freely, which requires both high dielectric constant and low viscosity. Cyclic carbonate esters have a high dielectric constant but high viscosity, while linear carbonate esters have low viscosity but low dielectric constant. Suitable electrolyte solutions are therefore obtained by mixing the two. 

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