Phenyl esters, from

The formation of phenyl esters from boronic acid and phenyhnagnesium bromide in THF is a fast liquid reaction involving contacting of two reactants, Rj (boronic acid) and R2 (phenyhnagnesium bromide), dissolved in the same solvent to yield a liquid mixture [48,108], This mixture is post-processed by a fast hydrolysis. This step was performed conventionally in a batch mode. 

The usual techniques of polyesterification, such as the solution31 or interfacial32 reaction between an aromatic acid chloride and bisphenol, are not applicable to the preparation of poly (phenyl esters) from hydroxybenzoic acids (prepared by an acid or phenyl ester exchange reaction of the acetate or phenyl ester of the acid33 ). 

Fig. 4. Energy minimum calculation of a docking experiment for two AT-propyl trimellitim-ide phenyl esters (from PCFF 91 forcefield of Biosym.)...

Acetylpyridinijum chloride Phenyl esters from phenyl ethers... 

Radical-cations may also be involved in the formation of phenyl esters from aromatic carboxylic acids and benzene in the presence of xenon difluoride, and can apparently be detected by e.s.r. spectroscopy during the reaction of iViV-dimethylaniline with perfluoropiperidine. The last reagent gives a low yield of o- and p-fluorophenol in the ratio 3.5 1 in its reaction with sodium phenoxide, and the predominance of ortho substitution is ascribed to a cage mechanism of the type shown in (3). However, towards 2,4,6-tri-t-butylphenoxyl radicals the piperidine acts as a source of fluorine atoms to give the dienone (4). ... 

Dissolve 5 g. of phenol in 75 ml. of 10 per cent, sodium hydroxide solution contained in a wide-mouthed reagent bottle or conical flask of about 200 ml. capacity. Add 11 g. (9 ml.) of redistilled benzoyl chloride, cork the vessel securely, and shake the mixture vigorously for 15-20 minutes. At the end of this period the reaction is usually practically complete and a sohd product is obtained. Filter oflf the soUd ester with suction, break up any lumps on the filter, wash thoroughly with water and drain well. RecrystaUise the crude ester from rectified (or methylated) spirit use a quantity of hot solvent approximately twice the minimum volume required for complete solution in order to ensure that the ester does not separate until the temperature of the solution has fallen below the melting point of phenyl benzoate. Filter the hot solution, if necessary, through a hot water funnel or through a Buchner funnel preheated by the filtration of some boiling solvent. Colourless crystals of phenyl benzoate, m.p. 69°, are thus obtained. The yield is 8 g. 

The SEM ester was used to protect a carboxyl group where DCC-mediated esterification caused destruction of the substrate. It was formed from the acid and SEM chloride (THF, 0°, 80% yield) and was removed solvolytically. The ease of removal in this case was attributed to anchimeric assistance by the phosphate group. Normally SEM groups are cleaved by treatment with fluoride ion. Note that in this case the SEM group is removed considerably faster than the phenyl groups from the phosphate. ... 

Phenyl esters can be prepared from A-protected amino acids (PhOH, DCC, CH2CI2, -20° 20°, 12 h, 86% yield PhOH, BOP, Et3N, CH2CI2, 25°, 2 h. 

The / -(methylmercapto)phenyl ester has been prepared from an /-protected amino acid and 4-tH3SC6H40H (DCC, CH2CI2, 0°, 1 h 20°, 12 h, 60-70% yield). The p-(methylmercapto)phenyl ester serves as an unactivated ester that is activated on oxidation to the sulfone (H2O2, AcOH, 20°, 12 h, 60-80% yield) which then serves as an activated ester in peptide synthesis. ... 

Phenyl esters can be prepared from A-protected amino acids (PhOH, DCC, CH2CI2, -20° 20°, 12 h, 86% yield PhOH, BOP, Et.N, CH2CI2, 25°, 2 h, 73-97% yield ). Phenyl esters are readily cleaved under basic conditions (H2O2, H2O, DMF, pH 10.5, 20°, 15 min). ... 

Phenolic compounds are weaker nucleophiles and better leaving groups than aliphatic alcohols. They do not yield polyesters when reacted with carboxylic acids or alkyl carboxy lates. The synthesis of polyesters from diphenols is, therefore, generally carried out through the high-temperature carboxylic acid-aryl acetate or phenyl ester-phenol interchange reactions with efficient removal of reaction by-product (Schemes 2.10 and 2.11, respectively). 

Values of /c2, the maximal rate constant for disappearance of penicillin at pH 10.24 and 31.5°, and Ka, the cycloheptaamylose-penicillin dissociation constant are presented in Table VII. Two features of these data are noteworthy. In the first place, there is no correlation between the magnitude of the cycloheptaamylose induced rate accelerations and the strength of binding specificity is again manifested in a rate process rather than in the stability of the inclusion complex. Second, the selectivity of cycloheptaamylose toward the various penicillins is somewhat less than the selectivity of the cycloamyloses toward phenyl esters—rate accelerations differ by no more than fivefold throughout the series. As noted by Tutt and Schwartz (1971), selectivity can be correlated with the distance of the reactive center from the nonpolar side chain. Whereas the carbonyl carbon of phenyl acetates is only two atoms removed from the phenyl ring, the reactive center... 

Zeolites have also been described as efficient catalysts for acylation,11 for the preparation of acetals,12 and proved to be useful for acetal hydrolysis13 or intramolecular lactonization of hydroxyalkanoic acids,14 to name a few examples of their application. A number of isomerizations and skeletal rearrangements promoted by these porous materials have also been reported. From these, we can underline two important industrial processes such as the isomerization of xylenes,2 and the Beckmann rearrangement of cyclohexanone oxime to e-caprolactam,15 which is an intermediate for polyamide manufacture. Other applications include the conversion of n-butane to isobutane,16 Fries rearrangement of phenyl esters,17 or the rearrangement of epoxides to carbonyl compounds.18... 

An additional example is the observed moderate acceleration in the cleavage of particular phenyl esters in the presence of a cyclodextrin. In such cases, the bound ester is attacked by an hydroxyl group on the cyclodextrin to yield a new ester. There was found to be a significant enhancement of phenol release from meta-substituted phenyl acetate on interaction with cyclodextrin (relative to other esters which do not fit the cavity so well) (Van Etten, Clowes, Sebastian Bender, 1967). During the reaction, the acyl moiety transfers to an hydroxyl group on the... 

The method outlined here competes well with the method developed earlier by Danheiser, et al.618 Its superiority is based on the fact that phenyl ester enolates give almost the same results as the S-phenyl thiolester enolates. However, handling the malodorous benzenethiol for the preparation of the active acid derivative and during workup of the p-lactone can be avoided. In addition, phenol is much cheaper than benzenethiol. The method is well suited for the preparation of p-lactones from symmetrical and unsymmetrical ketones. In addition to 3,3-dimethyM-oxaspiro[3.5]nonan-2-one, ( )-3-ethyl-1-oxaspiro[3.5]nonan-2-one and (3R, 4R )- and (3R, 4S )-4-isopropyl-4-methyl-3-octyl-2-oxetanone were prepared by this procedure in high yields (Notes 11 and 12). In the case of unsymmetrical ketones the less sterically crowded diasteroisomer is formed preferentially. With aldehydes as the carbonyl component the yields are unsatisfactory, because of the competitive formation of 1,3-dioxan-4-ones.6... 

If the snlfate anion-radical is bonnd to the snrface of a catalyst (sulfated zirconia), it is capable of generating the cation-radicals of benzene and tolnene (Timoshok et al. 1996). Conversion of benzene on snlfated zirconia was narrowly stndied in a batch reactor under mild conditions (100°C, 30 min contact) (Farcasiu et al. 1996, Ghencin and Farcasin 1996a, 1996b). The proven mechanism consists of a one-electron transfer from benzene to the catalyst, with the formation of the benzene cation-radical and the sulfate radical on the catalytic snrface. This ion-radical pair combines to give a snrface combination of sulfite phenyl ester with rednced snlfated zirconia. The ester eventually gives rise to phenol (Scheme 1.45). Coking is not essential for the reaction shown in Scheme 1.45. Oxidation completely resumes the activity of the worked-out catalyst. 

Figure 5 Energy diagram of ground and excited states of phenyl esters (r = reaction coordinate). (Adapted from Ref. 65.)...

The aromatic amides have attracted considerable interest from the photochemical point of view. However, anilides are less prone to photochemical rearrangements than the analogous phenyl esters. For this reason, the side reactions involving other parts of the molecule may compete favorably with PFR. Shizuka started the study of anilides in the 1960, and thereafter a number of papers have appeared dealing with the PFR of A -acyl anilines, carbazoles, indoles, and so forth. 

This appears to be a rather mixed collection of compounds. We recognize three isox-azolines in the collection. However, the data for the last two species, the cis and trans isomers of 3-phenyl-2-isoxazolinedicarboxylic acid dimethyl ester from Reference 67, are suspect because the difference of 125 kJmol is implausible—the corresponding difference for the cis and trans butenedioic acid dimethyl esters from Reference 68 is but ca 30kJmol-. ... 

From the point of view of quantum yields calculation, photo-Fries rearrangement, including phenol and products formation, represents a photoreaction (expressed by Eq. 3) in which all products absorb intensively in the absorption region of the starting phenyl ester A. 

Phenyl esters (RCOOAr) are not formed directly from RCOOH. Instead, acid chlorides or anhydrides are reacted with ArOH in the presence of strong base. 

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