Esters of diols

The reactions of olefins with peracids to form epoxides allows for the selective oxidation of carbon-carbon double bonds in the presence of other functional groups which may be subject to oxidation (for example, hydroxyl groups). The epoxides that result are easily cleaved by strong acids to diols or half-esters of diols and are therefore useful intermediates in the synthesis of polyfunctional compounds. 

The general procedures for the preparations of half-esters of diols are not usually very efficient in that both unreacted diol and diester are present along with the desired half-ester. Unfortunately, the present example is no exception but is included as an illustration of the type of results that can be expected under these circumstances. The diol employed for this reaction is prepared in Chapter 5, Section II. 

Methanol reacts with CO in the presence of a Ru3(CO)i2 catalyst to give methyl formate. Although methyl formate is produced in industry from methanol and CO using bases as catalysts, more efScient catalysts are needed [22b]. Eormic or acetic esters of diols are carbonylated to give lactones or hydroxylic ester with [Ru(CO)3l3]7r catalysts (Eq. 11.7) [23]. 

Crosslinking. To date, only a small number of crosslinkers have been tested as their poor miscibility with the monomers considerably limits the choice (Fig. 10) [92-99]. The most frequently used crosslinkers in acrylate systems are acrylate esters of diols and triols such as ethylene glycol dimethacrylate and trimethy-lolpropane trimethacrylate [92-94]. In styrene-based systems, isomers of di-vinylbenzene are usually used [61a, 62]. 

Cyclic allylboronate esters of diols can be obtained by reactions of appropriate diols or polyols (e.g. sugars) with activated triethylborane, or by photochemical combination of a trialkylborane with two equivalents of a secondary alcohol (Scheme 18). Conversion of alkenylboron compounds into alkenylmercury been extended to include allenyl and conjugated dienyl... 

Diol lipids have recently been detected in maize oil (seed oil from Zea mays) with the help of chromatographic methods [12]. It was evident that adsorption TLC was not capable of separating the esters and alkenyl ether esters of diols from the corresponding glycerol derivatives [12] (see also [22] and [9]). Using TLC, it was nevertheless possible to fractionate the products of alkaline methanolysis of the triglycerides of maize oil into three fractions methyl esters, alkenyl ethers and polyhydric alcohols. The alcohols could be separated and identified as their acetates by gas chromatography [12]. 

Triglycerides and esters of diols (diol lipids), compounds which cannot be separated by adsorption TLC, can be fractionated into classes through reversed phase partition TLC this applies equally to the corresponding alkoxylipids [9]. Chromatography on hydrophobic layers is also suitable for separating the aldehydic cores which are obtained from unsaturated lecithins by reductive ozonolysis [168] (see Fig. 147, p. 409) and for analysing sphingosine bases [129]. 

Other groups of substances have been noted, but further investigation is needed to ascertain their identification among the surest ones, we would mention plastoquinones with a structure close to that of vitamin Ki, detected in chloroplasts (Kegel, 1962) and in olive oil (Therrault, 1963) a group of phenolic substances, whose presence has been observed in at least two oils [in parsley oil, the myristicin (Privett et al., 1963), and in olive oil, the oleoeuropein (Vazquez Romero et al., 1961)] and the vinylic esters and esters of diols (propane-1,2- and 1,3-diol, butane-1,3- and 1,4-diol) these last are found in corn seeds and consequently in the oil also (Bergelson et al., 1966). 

Temaphthalene-dimethanol 34 is a unique compound with three naphthalene chromophores in chiral positions, and hence, the AC was determined from the exciton-coupled CD. To confirm the AC, the CSDP acid method was applied as follows. The CSDP esters of diol 34 were separated by HPLC with a = 1.2 (entry 22), and the AC of the second-eluted fraction was determined by X-ray crystallography. The (aR,aR) configuration of ( )-34 agreed with the assignment by the CD exciton chirahty method. 

Plasticizers. About 2.5% of U.S. adipic acid consumed in 1988 was used in two basic types of adipic ester based plasticizers (195). Simple adipate esters prepared from Cg—alcohols are used especially as PVC plasticizers (qv). Eor special appHcations requiring low volatility or extraction resistance, polyester derivatives of diols or polyols are preferred. 

Silver carbonate, alone or on CeHte, has been used as a catalyst for the oxidation of methyl esters of D-fmctose (63), ethylene (64), propylene (65), trioses (66), and a-diols (67). The mechanism of the catalysis of alcohol oxidation by silver carbonate on CeHte has been studied (68). 

A number of steroids have been regioselectively acylated ia a similar manner (99,104). Chromobactenum viscosum hpase esterifies 5a-androstane-3P,17P-diol [571-20-0] (75) with 2,2,2-triduoroethyl butyrate ia acetone with high selectivity. The hpase acylates exclusively the hydroxy group ia the 3-position giving the 3P-(monobutyryl ester) of (75) ia 83% yield. In contrast, bacillus subtilis protease (subtihsia) displays a marked preference for the C-17 hydroxyl. Candida iylindracea]i 2Lse (CCL) suspended ia anhydrous benzene regioselectively acylates the 3a-hydroxyl group of several bile acid derivatives (104). 

Adipoyl moiety is first attached ia order to provide an appropriately spaced proximal carbonyl group. The esters are oxidized enzymatically and then deacylated. The procedure results ia the synthesis of diols (119) with excellent enantiomeric purity (ee 96—98%) ia 72—92% yield. 

Mono MOM derivatives of diols can be prepared from the ortho esters by diiso-butylaluminum hydride reduction (46-98% yield). In general, the most hindered alcohol is protected. ... 

Disulfonate esters of vicinal diols sometimes undergo reductive elimination on treatment with sodium iodide in acetone at elevated temperature and pressure (usually l(X)-200°). This reaction derived from sugar chemistry has been used occasionally with steroids, principally in the elimination of 2,3-dihy-droxysapogenin mesylates. The stereochemistry of the substituents and ring junction is important, as illustrated in the formation of the A -olefins (133) and (134). 

Ozone. Most acetals are subject to cleavage with ozone, giving a mono ester of the original diol. 

Boronic esters are easily prepared from a diol and the boronic acid with removal of water, either chemically or azeotropically. (See Chapter 2 on the protection of diols.) Sterically hindered boronic esters, such as those of pinacol, can be prepared in the presence of water. Boronic esters of simple unhindered diols are quite sensitive to water and hydrolyze readily. On the other hand, very hindered esters, such as the pinacol and pinanediol derivatives, are exceedingly difficult to hydrolyze and often require rather harsh conditions to achieve cleavage. 

Boric acid esters provide for thermal stabilization of low-pressure polyethylene to a variable degree (Table 7). The difference in efficiency derives from the nature of polyester. Boric acid esters of aliphatic diols and triols are less efficient than the aromatic ones. Among polyesters of aromatic diols and triols, polyesters of boric acid and pyrocatechol exhibit the highest efficiency. Boric acid polyesters provide inhibition of polyethylene thermal destruction following the radical-chain mechanism, are unsuitable for inhibition of polystyrene depolymerization following the molecular pattern and have little effect as inhibitors of polypropylene thermal destruction following the hydrogen-transfer mechanism. 

The inhibitive efficiency of boric acid polyesters differs greatly. The highest efficiency is exhibited by polyesters of boric acid, aromatic diols and triols. This derives from the fact that in this case the radicals are accepted not only by boron, but also by the aromatic nucleus. Among the aromatic polyesters, most efficient is ester of boric acid and pyrocatechin due to the Frank-Rabinovich cage effect. The efficiency of inhibi-... 

Polybibenzoates are a kind of thermotropic polyesters obtained by polycondensation of 4,4 -biphenyldicar-boxylic acid (p,p -bibenzoic acid) with a diol. These polyesters contain the biphenyl group, which is one of the simplest mesogens. They are synthesized by melt transesterification of the dimethyl or diethyl ester of p,p -bibenzoic acid and the corresponding diol, using a titanium compound as catalyst, according to the following scheme ... 

Polyesters can be produced by an esterification of a dicarboxylic acid and a diol, a transesterification of an ester of a dicarboxylic acid and a diol, or by the reaction between an acid dichloride and a diol. 

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