2- benzoate esters

By the use of substituted benzoyl chlorides, derivatives such as the penta-O-(p-bromobenzoyl)- and penta-0-(p-nitrobenzoyl)-D-glucoses have been prepared. 

The use of boric acid has been suggested by Brigl for the preparation of partially 0-benzoylated sugars (41, 44)- Unimolar 0-benzoylation of glycosides and mercaptals results usually in preferential esterification of the primary hydroxyl (45). 

A nonreducing di-0-benzoyldisaccharide containing D-glucose and d-xylose residues has been reported (47) as occurring in Daviesia latifolia, an Australian shrub. 

From the biological standpoint, 1-mono-O-benzoyl-D-glucuronic acid is the most important benzoyl derivative. This compound occurs in the urine of dogs fed benzoic acid. Its structure was shown by the following evidence 

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The following equation shows an example of a mixed Claisen condensation m which a benzoate ester is used as the nonenohzable component... 

The irradiation of the provitamin has been achieved using the acetate and benzoate esters, although the free alcohol form of the provitamin is usually used (77). 

Benzyl alcohol, [100-51 -6] C H CH20H (bp, 205.4°C at 101.3 kPa), produced by the hydrogenation of benzaldehyde is used in color photography as a parenteral solution preservative as a general solvent and as an intermediate in the manufacture of various benzoate esters for the soap, perfume, and flavor industries (see Benzyl alcohol and P-phenethyl alcohol). 

Production of cellulose esters from aromatic acids has not been commercialized because of unfavorable economics. These esters are usually prepared from highly reactive regenerated cellulose, and their physical properties do not differ markedly from cellulose esters prepared from the more readily available aHphatic acids. Benzoate esters have been prepared from regenerated cellulose with benzoyl chloride in pyridine—nitrobenzene (27) or benzene (28). These benzoate esters are soluble in common organic solvents such as acetone or chloroform. Benzoate esters, as well as the nitrochloro-, and methoxy-substituted benzoates, have been prepared from cellulose with the appropriate aromatic acid and chloroacetic anhydride as the impelling agent and magnesium perchlorate as the catalyst (29). 

A formate ester can be cleaved selectively in the presence of an acetate [(MeOH, 1 eflux) ordil. NH3 (formate is 100 times faster than an acetate) ] or benzoate ester (dil. NHg). ... 

The benzoate ester is one of the more common esters used to protect alcohols. Benzoates are less readily hydrolyzed than acetates, and the tendency for benzoate migration to adjacent hydroxyls, in contrast to acetates, is not nearly as strong. Benzoates can be forced to migrate to a thermodynamically more stable position. ... 

A benzoate ester can be cleaved in 60-90% yield by electrolytic reduction at -2.3... 

This method is also effective in the selective introduction of a benzoate ester. 

The most satisfactory derivatives for phenols that are of low molecular weight or monohydric are the benzoate esters. (Their acetate esters are generally liquids or low-melting solids.) Acetates are more useful for high molecular weight and polyhydric phenols. 

The potential for use of chiral natural materials such as cellulose for separation of enantiomers has long been recognized, but development of efficient materials occurred relatively recently. Several acylated derivatives of cellulose are effective chiral stationary phases. Benzoate esters and aryl carbamates are particularly useful. These materials are commercially available on a silica support and imder the trademark Chiralcel. Figure 2.4 shows the resolution of y-phenyl-y-butyrolactone with the use of acetylated cellulose as the adsorbent material. 

Even alkyl benzoate esters give only a small amount of exchange imder basic hydrolysis conditions. This means that reversal of the hydroxide addition must be slow relative to the forward breakdown of the tetrahedral intermediate. ... 

Mixed Claisen condensations (Section 21.3) Diethyl carbonate, diethyl oxalate, ethyl formate, and benzoate esters cannot form ester enolates but can act as acylating agents toward other ester enolates. 

Taft began the LFER attack on steric effects as part of his separation of electronic and steric effects in aliphatic compounds, which is discussed in Section 7.3. For our present purposes we abstract from that treatment the portion relevant to aromatic substrates. Hammett p values for alkaline ester hydrolysis are in the range +2.2 to +2.8, whereas for acid ester hydrolysis p is close to zero (see Table 7-2). Taft, therefore, concluded that electronic effects of substituents are much greater in the alkaline than in the acid series and. in fact, that they are negligible in the acid series. This left the steric effect alone controlling relative reactivity in the acid series. A steric substituent constant was defined [by analogy with the definition of cr in Eq. (7-22)] by Eq. (7-43), where k is the rate constant for acid-catalyzed hydrolysis of an orr/to-substituted benzoate ester and k is the corresponding rate constant for the on/to-methyl ester note that CH3, not H, is the reference substituent. ... 

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