Cyclic aromatic esters

The mechanism of this reaction has been studied by several groups [133,174-177]. The consensus is that interaction of ester with the phenolic resole leads to a quinone methide at relatively low temperature. The quinone methide then reacts rapidly leading to cure. Scheme 11 shows the mechanism that we believe is operative. This mechanism is also supported by the work of Lemon, Murray, and Conner. It is challenged by Pizzi et al. Murray has made the most complete study available in the literature [133]. Ester accelerators include cyclic esters (such as y-butyrolactone and propylene carbonate), aliphatic esters (especially methyl formate and triacetin), aromatic esters (phthalates) and phenolic-resin esters [178]. Carbamates give analogous results but may raise toxicity concerns not usually seen with esters. 

Table 5 summarizes the reactions of isoprene with aromatic aldehydes and unsaturated aldehydes. Salicylaldehyde provides the expected product as a cyclic boric ester derivative and shows apparently lower stereoselectivity, giving a mixture of 1,3-anti and 1,3-syn isomers in a ratio of 6 1 (run 1, Table 5). 2-Furfural reacts as usual and provides a 1,3-anti isomer as a single diastereomer in good yield (run 2). Unsaturated aldehydes, irrespective of their substitution patterns, undergo homoallylation selectively with excellent 1,3-anti selectivity, the geometry of the double bond of the starting aldehydes remaining intact (runs 3-5). 1,2-Addition to unsaturated aldehyde takes place selectively and no 1,4-addition is observed.

Hamilton, S. C., Semiyen, J. A. and Haddleton, D. M., Cyclic polyesters 8. Preparation and characterization of cyclic oligomers in six aromatic ester and ether-ester systems, Polymer, 39, 3241 (1998). 

Quinolinium dichromate (QDC) oxidations of primary and secondary alcohols both proceed via a cyclic chromate ester. Acrylonitrile polymerization was observed in the oxidation of several para- and meffl-substituted benzaldehydes to the corresponding benzoic acids by quinolinium chlorochromate (QCC). QCC oxidations of diphenacyl sulfide and of aromatic anils have been studied. 

The aldol-type reaction of a cyclic enol ester, 5-methyl-2(3//)-furanone (4b), was carried out with three kinds of catalytic systems PdCl2 (PhCN)2-SnCl2, Ni(Cod)2/Ph3P-Zn, and Pd(OAc)2/PPh3-Zn. In the presence of the first catalyst, aromatic aldehydes condense with 4b to give ds-)3-acetyl-y-aryl-y-butyrolactones (47), but alkanals are mainly con-... 

Food, flavors consist of numerous compounds, none of which alone is characteristic of specific food. Classes of compounds which emcompass food flavors are - hydrocarbons (aliphatic, ali-cyclic, aromatic) carbonyls (aldehydes, ketones) carboxylic acids, esters, imides, anhydrides alcohols, phenols, ethers alkylamines, alkylimines aliphatic sulfur compounds (thiols, mono-, di- and tri-sulfides) nitrogen heterocyclics (pyrroles, pyrazines, pyridines) sulfur heterocylics (thiophenes, thiazoles, trithiolane, thialidine) and oxygen-heterocyclics (lactone, pyrone, furan). Discussion will be limited to striking developments in heterocyclics. 

Voltammetric data for ester reductions are available for several aromatic esters [51-54], and in particular cyclic voltammetry shows clearly that in the absence of proton donors reversible formation of anion radical occurs [51]. In dimethylfonnamide (DMF) solution the peak potential for reduction of methyl benzoate is —2.29 V (versus SCE) for comparison dimethyl terephthalate reduces at —1.68 V and phthalic anhydride at —1.25 V [4]. Half-wave potentials for reduction of aromatic carboxylate esters in an unbuffered solution of pH 7.2 are linearly correlated with cr values [51] electron-withdrawing substituents in the ring or alkoxy group shift Ei/o toward less negative potentials. Generally, esters seem to be more easily reducible than the parent carboxylic acids. Anion radicals of methyl, ethyl, and isopropyl benzoate have been detected by electron paramagnetic resonance (epr) spectroscopy upon cathodic reduction of these esters in acetonitrile-tetrapro-pylammonium perchlorate [52]. The anion radicals of several anhydrides, including phthalic anhydride, have similarly been studied [55]. 

In addition to water, these paints contain biocides, surfactants, pigments, monomers, coalescing solvents, driers, and volatile additives. 3,121 Volatile components contained in these include aldehydes, aliphatic hydrocarbons (straight chain and cyclic), aromatic hydrocarbons, esters, ethers, glycol ethers, glycol ether esters, and halogenated hydrocarbons. Some of these materials are listed in Table 12.4. 

Carbonyl groups of simple aliphatic aldehydes, ortho mdpara quinones, a,P-unsaturated carbonyls and cyclic aromatic anhydrides are known to condense with trimethyl phosphite, producing phosphite esters [62]. Lebo and Lonsky used trimethyl phosphite to determine the light-induced formation of ort/jo-quinonoid functional groups in refiner mechanical pulp [63]. 

Sulfonamides as ortho-directing substituents for metalating aromatic systems opened the door to synthetic routes to cyclic sulfonic esters (sultones) and amides (sultams). The first step in this procedure for preparing sultams involved the 2-metalation of N-alkylbenzenesulfonam-ides (52) and condensation with a variety of ketones. The tertiary alco-... 

Ai3-18365 Carbonic acid, cyclic ethylene ester CCRIS 293 Cyclic ethylene carbonate Dioxolone-2 EINECS 202-510-0 Ethylene carbonate Ethylene carbonic acid Ethylene glycol carbonate Ethylene glycol, cyclic carbonate Ethylenester kyseiiny uhlicite Glycol carbonate HSDB 6803 NSC 11801 Texacat EC. Solvent for organic and Inorganic material ERA Rule 66 exempt also used as reactant and plasticizer in fibers and textiles, plastics and resins, aromatic hydrocarbon extraction, electrolytes, hydraulic brake fluids. Plates mp = 36.4" bp = 248° = 1,3214 freely soluble in H2O,... 

The RTV silicones, in general, exhibit considerably greater outgassing of both condensable and noncondensable materials than the HV silicones. Their condensable-time curves were usually linear and only one condensable product was being evolved. The Infrared spectra of the condensable products from all of the silicones evaluated indicated these materials to be predominately low molecular weight alkyl linear and/or cyclic polysiloxanes (Table II). Silicone A gave a nonlinear condensable-time curve and evolved two types of condensable products an alkyl linear and/or cyclic polysiloxane, and an aromatic ester. 

A number of classes of additives specifically for use as UV absorbers in polymer formulations are available including, among the better known ones, aromatic salicylates [11], o-hydroxybenzophenones [12], 2-hydroxyphenylbenzotriazoles [12,13], derivatives of cinnamic acid and related materials [14,15], aromatic oxanilides [16], cyclic imino ester derivatives known varionsly as benzoxazines or benzoxazones [17, 18] and hydroxyphenyltriazines [19]. 

In the mid 1960 s, Prochaska was granted several patents for the preparation of monomeric cyclic aromatic carbonates with 7- or 8-membered rings, formed from 2,2 -biphenols (Equation 7).l The monomeric cyclic carbonates could be prepared either directly, via phosgenation, or using a vacuum distillation/depolymerization technique similar to that developed by Carothers for the preparation of cyclic aliphatic esters and... 

Periasamy et at. obtained aldehydes in good yield from poly-cyclic aromatic hydrocarbon radical anions prepared by the addition of sodium to the aromatic hydrocarbon in THF, followed by formylation with carboxylic acid esters or N,N-dialkyformamides. Reactions of sodium naphthalenide, -anthracenide and -phenan-threnide with ethyl formate yielded the corresponding aldehydes. Substituted naphthalenes e.g. acenaphthene and 2-methylnaphthalene are also formylated using A/,A/-dialkylformamides, but in low yields (20% and 26% respectively). 

Bis(maleimides) prepared from aromatic diamines (benzidine, p-phenylcne-diamine, o-tolidine, o-anisidine) were condensed with 1,8-diphenyloctatetraene and related bis(dienes). Polymers that softened above 300°C with molecular weights of approximately 3000 were obtained (18). A Diels-Alder polymerization has been described that yields a ladder polymer. The cyclic oligomeric esters [13] and [14] give low molecular weight polymer when heated in toluene (7). p-Benzoquinone has also been polymerized with [14]. A chloroform-soluble product with a molecular weight of about 2000 was obtained (7). 

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