Esters and carbonates

Villemin (1980) first demonstrated the occurrence of the RCM reaction (12) to form a 16-membered unsaturated lactone. 

ADMET polymerization reactions of this and other diene esters, also carbonates, are listed in Table 8.6. As with monoene esters, for reaction to occur there must be more than one methylene group between the double bond and the ester (or carbonate) group. The inhibition by a proximate ester group may be a polarization effect hindering the formation and/or the rearrangement of the intermediate metallacycle, or it may result from a coordination of the carbonyl oxygen to the metal centre (Patton, J.T. 1992). 

Main-chain ferroelectric liquid crystal oligomers (MW 6000) have been made by the ADMET polymerization of H2C—CH(CH2)70C6H4C6H4C00C6H3(N02) OCHMe(CH2) CH=CH2(M = 2-4) using 18 at 80°C as a catalyst (Walba 1996). 

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Mercaptothiazolines ate obtained from the corresponding sulfate esters and carbon disulfide,... 

A convenient method of compositional designation uses molar percentages of ester and carbonate linkages coupled with the molar percentages of iso- and terephthalate units in the polymer. A 70% ester, 30% carbonate polyester carbonate with 60 parts of isophthalate and 40 parts of terephthalate is designated 70(60/40)30. Similarly, a standard PC resin is 0(0/0)100, and a polyarjlate resin composed of a 1 1 molar ratio of iso- to terephthalate units esterfied with bisphenol A is designated 100(50/50)0. 

Cd-Pb, AcOH, 89-94% yield.This reagent also cleaves trichloroethyl esters and carbonates. 

Figure 4 Schematic representation of the structural features of the HpD oligomer (drawn as a tetramer), showing ether, ester and carbon-carbon internuclear bonds.

The preparation of hydroxy-terminated styrylpyridine has been described previously (18). The model esters and carbonate were prepared by an interfacial reaction. The scheme for the reaction was as follows ... 

Photo-Fries Rearrangement of Styrylpyridine Based Ester and Carbonate-UV-Spectroscopic Studies... 

The ultraviolet (UV) rearrangement of polyarylesters and their related model compounds have been previously studied (20,21). The chemical changes which occur during the UV irradiation of styrylpyridine based ester and carbonate were investigated. The UV spectra of the p-VPPB and p,p -BVPDPC in 1,2-dichloroethane were monitored during the irradiation (Fig. 3 and 4). The maximum absorption for unirradiated p-VPPB was at 319 nm. After UV irradiation, the maximum peak shifted from 319 nm to 350 nm and the observed increased absorption in the... 

The question P.G. Schultz, from Berkeley, and R.A.Lemer, from Scripps, set forth was "How to associate the prodigious capacity of molecular recognition of antibodies with potential enzymatic (catalytic) activity " [22a] [26]. In 1986, they succeeded developing the first antibodies with catalytic activity [27]. Lemer called them abzymes. In fact, their strategy is quite simple based on Pauling s hypothesis, Lerner s and Schultz s groups looked for antibodies that could stabilise the transition state of a given reaction, such as ester and carbonate hydrolysis. 

A huge number of ester and carbonate derivatives of polynitroaliphatic alcohol have been synthesized driven by the search for new explosives and energetic plasticizers and oxidizers for propellant and explosive formulations. Most of these are derived from 2-fluoro-2,2-dinitroethanol and 2,2,2-trinitroethanol ° and have excellent oxygen balances. Some examples are illustrated above (168-174) but more comprehensive lists can be found in numerous reviews. " " Direct esterification of polynitroaliphatic alcohols with nitric acid, mixed acid, or acetic anhydride-nitric acid has been used as a route to mixed polynitroaliphatic-nitrate ester explosives. ... 

An extremely mild method for the synthesis of nitrate esters from easily oxidized or acid-sensitive alcohols involves the decomposition of a nitratocarbonate (29). The nitratocar-bonate is prepared in situ from metathesis between a chloroformate (reaction between phosgene and an alcohol) and silver nitrate in acetonitrile in the presence of pyridine at room temperature. Under these conditions the nitratocarbonate readily decomposes to yield the corresponding nitrate ester and carbon dioxide. Few examples of these reactions are available in the literature and they are limited to a laboratory scale. 

N other-(c=o)- is the number of C=O groups in ester and carbonate moieties as well as in anhydride groups. 

The distribution of by-products originating from the methyl group in acetaldehyde oxidation is significantly different for each catalyst. Typical results are presented in Table II. Methane is the predominant by-product with cobalt acetate, while methane and carbon dioxide and methyl esters and carbon dioxide predominate with manganese and copper acetates, respectively. 

Palladium-catalysed chemo- and enantio-selective oxidation of allylic esters and carbonates has been achieved using nitronates as nucleophilic oxidants. The products, o /3-unsaturalcd carbonyl compounds, were obtained in excellent yields and ees. The mechanism in Scheme 5 has been suggested for the reaction.108... 

Esters, and Carbonate Solutions Containing Lithium Ions with Noble Metal Electrodes (Ag, Au, Pt) [7-12,14]... 

Most thiol protecting groups in common use are 5-alkyl derivatives because thiol esters and carbonates are much more easily hydrolysed than their oxygen counterparts. 

The utility of thiol esters and carbonates as protecting groups is limited by their vulnerability to hydrolysis, The poor overlap between the non-bonded electrons on the sulfur atom (3p) and the n-system of the carbonyl (2p) precludes or diminishes resonance stabilisation of the type enjoyed by normal esters thereby raising their ground state energy, The carbonyl group of the thioester is more electrophilic than a normal ester and hence more reactive. Thiocarbonate derivatives are marginally more stable. The 5-benzoyl derivative of cysteine is 95% hydrolysed in 30 minutes with 2 M ammonia whereas the 5-benzyloxycarbonyl derivative is only 20% hydrolysed in 30 minutes under the same conditions.54... 

Mixed carboxylic-carbonic anhydrides decompose in the presence of DMAP to give esters and carbon dioxide under mild conditions [Scheme 6,51], In the case of benzyl esters, the mixed car boxy lic-car bon ic anhydrides can be generated by reaction of the carboxylic acid with benzyl chloroformate in the presence of triethylamine (1.1 equiv) and DMAP (0.1 equiv)126 or more conveniently by reaction of the carboxylic acid with dibenzyl dicarbonate (dibenzyl pyrocarbo-nate) in THF or ferf-butyl alcohol in the presence of DMAP (0.1 equiv).127 The reactions generally work well except for hindered carboxylic acids. The method can also be used to make methyl, ethyl, ferf-butyl and ally esters. Carboxylic acids react with 2 equivalents of benzyl 2,2t2-trichloroacetimidate12s in the presence of a catalytic amount of boron trifluoride etherate to give the benzyl ester in modest to good yield,12g... 

The tertiary butyl ester and carbonate groups are particularly useful in this application because they are sensitive to A l-I hydrolysis that does not require a stoichiometric amount of water. These materials undergo acid-catalyzed thermolysis. Consequently, a resist system can be formulated by casting these polymers from solutions that also contain a substance that... 

Methylation derivatization also has been successfully used for the transmethylation of esters and carbonates. For an ester, the reaction can take place by the following mechanism ... 

Besides cyclic esters and carbonates, six-membered cyclic depsipeptides and a five-membered cyclic phosphate were subjected to lipase-catalyzed ring-opening polymerizations, yielding poly (ester amide)s190 and polyphosphate,191 respectively. High temperatures (100—130 °C) were required for the polymerization of the former monomers. 

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