Benzyl acetate hydrolysis

The quinone methide can also be generated in situ, at least in aqueous NaOH, directly from the peracetate, as hydrolysis of the phenolic acetate is faster than the benzylic acetate (see an example in Section 12.5.3). This method was used to demonstrate the addition of anthrahydroquinone (AHQ) and anthranol to (actual polymeric) lignin quinone methides in studies elucidating the anthraquinone (AQ)-catalyzed 8-0-4-aryl ether cleavage mechanisms in alkaline pulping.64-66... 

Reduction of the complex on Raney nickel yielded benzylamine, N-methyl-benzylamine, and N,N-dimethylbenzylamine but no / -phenylbenzylamine, a reduction product resulting under the same reaction conditions from benzyl cyanide. Hydrolysis with dilute sulfuric acid in acetic acid yielded benzylamine only, and oxidation of the complex with potassium permanganate gave 4.2 moles of benzoic acid per mole of complex. The bromide anion can be exchanged metathetically with various other anions such as perchlorate, iodide, and thiocyanate. When heated at 100° C. in vacuum, the complex lost one mole of benzyl bromide and yielded only one dicyanotetrakis(benzylisonitrile)iron(II) complex. 

The metabolism of benzyl acetate involves very rapid hydrolysis to acetate and benzyl alcohol. The latter is subsequently mainly oxidized to benzaldehyde and benzoic acid. A small part of the benzyl alcohol may be conjugated with sulfate, leading, ultimately, to fonnation of a glutathione conjugate that is excreted as mercapturate in urine. The benzoic acid is excreted mainly as hippurate and, to a lesser extent, as acyl glucuronide (see Figure 1). 

Since no data are available on humans except for skin penetration data in vitro, no direct comparison can be made. Because in humans most of the dose seems to be excreted as hippurate (lARC, 1986) and because the metabolism of the primary hydrolysis product of benzyl acetate, benzyl alcohol, is very similar in rodents and humans (see, e.g., the monograph on toluene (this volume)), it is to be expected that the fate of benzyl acetate in humans is very similar to that in rodents. 

A rather similar result has been obtained much more recently by Sadek et a/.108. These authors carried out a detailed investigation of the hydrolysis of benzyl acetate in aqueous dioxan, varying the solvent composition, and also the temperature (from 25 to 45°C). In the low-acidity region used (0.05 M HC1) the ester is hydrolyzed by the Aac2 mechanism, and the solvent effects are probably typical. The rate of hydrolysis decreases steadily as the proportion of dioxan in the medium is increased, as a result of a steady increase in AH, which is only partially offset by an increasingly favourable entropy of activation. However, the increase in AS1 eventually levels out at about 70% w/w dioxan, as illustrated by the data for 30°C ... 

As has already been illustrated in Sect. 2.1, carbons with their graphitic surface structure often adsorb aromatic compounds well and thereby affect their reaction rates. In order to test what influence carbons would have on the solvolysis of an aromatic ester, Spiro and Mills [172] carried out exploratory experiments on the alkaline hydrolysis of benzyl acetate at 25°C... 

In a synthesis of Epothilones A and B, Danishefsky and co-workers used a triphenylsilyl ether to protect a hindered secondary alcohol in a long sequence that included DDQ deprotection of a benzyl ether, dithiane hydrolysis, dimethyl acetal hydrolysis with p-toluenesulfonic acid in dioxane-H20 (5 1) at 50 °CT... 

For styrene-based random copolymers, functional groups can be introduced into the polymer chains via copolymerization with functional styrene derivatives, because the electronic effects of the substituents are small in the metal-catalyzed polymerizations in comparison to the ionic counterparts. Random copolymer R-6 is of this category, synthesized from styrene and />acetoxystyrene.372 It can be transformed into styrene// -vinylphenol copolymers by hydrolysis.380 The benzyl acetate and the benzyl ether groups randomly distributed in R-7 and R-8 were transformed into benzyl bromide, which can initiate the controlled radical polymerizations of styrene in the presence of copper catalysts to give graft copolymers.209 Epoxy groups can be introduced, as in R-9, by the copper-catalyzed copolymerizations without loss of epoxy functions, while the nitroxide-mediated systems suffer from side reactions due to the high-temperature reaction.317... 

In a second example, the authors demonstrated the use of subcritical water as a solvent in the selective hydrolysis-free O-acylation of alcohols. Using a reaction temperature of 200 °C and a pressure of 5 MPa, the acylation of benzyl alcohol (28) using acetic anhydride (29) was achieved in <10 s (Scheme 6.7). Under the aforementioned conditions, the target compound benzyl acetate (30) was obtained in 99% yield, representing a dramatic increase of 82% compared with analogous batch processes. 

Nitrobcnzyl alcohol has been secured by the oxidation of -nitrotolucne electrolytically1 or chemically,2 and by the hydrolysis of the acetate.3 4 -Iodobenzyl alcohol has been prepared by the hydrolysis of -iodobenzyl bromide and />-iodo-benzyl acetate.5 0... 

Epoxidation of the olefin occurs with high diastereofacial selectivity to give carbamoyl-oxirane 945. This epoxide is not extremely stable, and is treated directly with methanesulfonic acid to afford the j5-D- a/o-furanoside 946. The stereocenter at C-2 must be inverted to match the configuration of the natural product. This is accomplished by triflate formation followed by an Sn2 reaction with cesium acetate. Hydrolysis of the OAc group furnishes the desired P D-ga/ac o-furanoside (947). 0-Methylation, benzyl group hydrogenolysis, acidic hydrolysis, and dithioacetal formation completes the synthesis of 948 in 11 steps and 5.7% overall yield from 929 [252]. 

The diversity associated with silyl protecting groups as well as the chemical conditions available for their removal makes them attractive alternatives to benzyl protection of the hydroxy groups of either D- or L-tartaric acid derivatives. O-isopropylidene-L-threitol (37) is mono-protected with er -butyldimethylsilyl chloride to furnish 266, which is converted in three steps to the nitrile 267. Reduction with DIBAL and Wittig olefination followed by desilylation with fluoride and Swern oxidation of the resulting alcohol provides aldehyde 268, which reacts with methyl 10-(triphenylphosphorane)-9-oxo-decanoate (269) to afford enone 270. Reduction of 270 with subsequent preparative TLC and acetal hydrolysis furnishes (9R)-271 and (9 S)-272, both interesting unsaturated trihydroxy Cig fatty acid metabolites isolated from vegetables [91] (Scheme 62). 

The STaz moiety was found stable toward common protecting group manipulations involving basic and acidic conditions, for example, acetylation, benzylation, acetal formation and cleavage, etc. (77). The STaz derivatives were found to be stable toward hydrolysis in the presence of acidic thiophilic reagents. Thus, comparative hydrolytic stability studies showed that STaz glycosides are even more stable than their 1-5-ethyl and 1-5-phenyl counterparts in the presence ofNBSorNlS/TfOH. 

The enantiomer of 72 (ent-72) was synthesized from the same starting material 106 fScheme 12.37). Benzylation of a hydroxy group in 106 followed by acetal hydrolysis afforded 140, which was converted into 5-enop)Tanoside 141 by the conventional method. The Ferrier carbocyclization of 141 generated 142 as a diastereomeric mixture in 83% yield. Protection of the hydroxy group in 142 as a THP ether and subsequent reduction of the ketone carbonyl gave 143. 0-Mesylation of 143 followed by acidic work-up afforded 144. Swern oxidation of 144 was accompanied by the p-elimination of the OMs group to furnish ent-72 in 93% yield. Cyclohexenone ent-72 could be used for the synthesis of natural enantiomer of actinoboline. 

The value of the Hammett equation in estimating reaction rates is illustrated as follows. Suppose it is required to know the rate of alkaline hydrolysis of p-nitrobenzyl acetate in 56% acetone at 25°C. p for the general reaction is +0.760 and the rate constant for the hydrolysis of benzyl acetate is 6.995 X 10 1 mole" sec". The substituent constant for p-nitro is +0.778. The required rate constant is obtained from the equation ... 

Ali, S. H. S. Q. Merchant (2009) Kinetic study of dowex 50 Wx8-catalyzed esterification and hydrolysis of benzyl acetate. Industrial Engineering Chemistry Research, 48, 2519-2532,ISSN 0888-5885. 

NBS, CH3CN, H2O, 62-90% yield.The POM group has been selectively removed in the presence of an ethoxy ethyl ether, TBDMS ether, benzyl ether, p-methoxybenzyl ether, an acetate, and an allyl ether. Because the hydrolysis of a pentenyl 2-acetoxyglycoside was so much slower than a pentenyl 2-benzyloxyglycoside, the 2-benzyl derivative could be cleaved selectively in the presence of the 2-acetoxy derivative. The POM group is stable to 75% AcOH, but is cleaved by 5% HCl. 

A benzylidene acetal is a commonly used protective group for 1,2- and 1,3-diols. In the case of a 1,2,3-triol the 1,3-acetal is the preferred product. It has the advantage that it can be removed under neutral conditions by hydrogenolysis or by acid hydrolysis. Benzyl groups and isolated olefins have been hydrogenated in the presence of 1,3-benzylidene acetals. Benzylidene acetals of 1,2-diols are more susceptible to hydrogenolysis than are those of 1,3-diols. In fact, the former can be removed in the presence of the latter. A polymer-bound benzylidene acetal has also been prepared." ... 

Historically, simple Vz-alkyl ethers formed from a phenol and a halide or sulfate were cleaved under rather drastic conditions (e.g., refluxing HBr). New ether protective groups have been developed that are removed under much milder conditions (e.g., via nucleophilic displacement, hydrogenolysis of benzyl ethers, and mild acid hydrolysis of acetal-type ethers) that seldom affect other functional groups in a molecule. 

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