Aryl benzoates

Aryl benzoates, stable to alkylation conditions using K2C03/Mc2S04, are cleaved by more basic hydrolysis (KOH). They are stable to anhydrous hydrogen chloride, but are cleaved by hydrochloric acid. ... 

CH3 Cl aq. NaHC03 or aq. NaOH, 80% yield. This reagent forms aryl benzoates under aqueous conditions. (It also acylates amines and carboxylic acids.)... 

Rate Constanta for the Two Steps of the Reaction of Cydohexaamylose with Aryl Benzoates at pH 10.60 and 25°a... 

Capon and Ghosh, 1966. No appropriate reference intermolecular reaction rate has been measured for an aryl benzoate. The reference used is the intramolecular general base-catalysed hydrolysis of salicyl salicylate (Kemp and Thibault, 1969) which has fchyd = 2.89 x 10-6 s-1 in water at 30°. If the EM is assumed to be the same as for aspirin (13 M) this corresponds to an intermolecular reaction of an aryl benzoate catalysed by benzoate with k2 = 2.22 x 10-7 dm3 mol-1 s 1. The correction from the pA"-value of salicyl salicylate (3.6) to the pA", of the substrate uses / = 0.5 (cf. 0.52 for the aspirin reaction). The temperature sensitivity is also taken to be equal to that of the aspirin reaction... 

A double displacement reaction (27) was shown to occur with aryl benzoates (Van Etten, 1967b). 

A Bac2 mechanism is proposed for die saponification of ethyl benzoate in ethanol-water.37 The reactions of aryl benzoates in absolute ethanol with ethoxide, aryloxides and acetophenone oximates occur via a stepwise mechanism in which the formation of the tetrahedral intermediate is rate determining.38 A stepwise mechanism is also supported for the reactions of /7-nitrophenyl-substituted benzoates with hydroxide and / -chlorophcnoxidc. The evidence comes from breaks in Hammett plots as the acyl... 

A reduction parameter 8 of 0.091 corresponds to a 10 % increase in peak variance. The dependence of the peak width on the injected plug length for alkyl and aryl benzoates in packed CEC was investigated experimentally [30]. At low injection plug... 

In addition to halides, leaving groups can be other OR, and so on, even OH. Acid salts, RCOO, are sometimes used as nucleophiles. Good yields of aryl benzoates can be obtained by the treatment of aryl halides with cuprous benzoate in diglyme or xylene at 140-160°C. " Unactivated substrates have been converted to carboxylic esters in low-to-moderate yields under oxidizing condi-... 

Olah and coworkers have shown that Nafion-H, a perfluorinated resinsulfonic acid, acts as an efficient catalyst for the Fries rearrangement of aryl benzoates. For example, meta-chlorophenyl benzoate undergoes Fries rearrangement in the presence of Nafion-H... 

Benzenediols—see also Acylbenzenediols, Alkylbenzenediols, Chlorobenzenediols, Dihydroxybenzenes, Nitrobenzenediols thermochemistry of 242-246 Benzimidazoles, hydrogen transfer in 1025 Benzoates—see Aryl benzoates, Heptabenzoates... 

Figure 6 Hydrolysis of aryl benzoates by alkali has a transition structure located at an edge of the reaction surface...

Under anhydrous conditions, cesium carbonate or bicarbonate quantitatively cleaves an aryl dibenzoate or diacetate to the monoester yields are considerably lower with potassium carbonate. K2CO3 in NMP at 100"C results in selective cleavage of aryl benzoates and acetates, but does not hydrolyze other... 

Aryl benzoates are subject to acyl migration under basic conditions. ... 

Diaryliodonium salts react with sodium benzoate to give the aryl benzoates in moderate to good yields (40-85%). Treatment of biphenyleneiodonium sulfate (29) with sodium methoxide failed to give 2-iodo-2 -methoxybiphenyl. However, this product was obtained by an indirect sequence involving the formation of 2-iodo-2 -acetoxybiphenyl (30) by reaction of the biphenyleneiodonium sulfate with sodium acetate in boiling glacial acetic acid. Nearly quantitative yields were obtained when the reaction was catalysed by copper salts. 102... 

There are several closely related processes involving other nucleophiles that, at least to date, have found less synthetic application. For example, heating aryl halides with cuprous benzoate produces aryl benzoates ... 

SCHEME 31 PFR in liquid crystaUine polymethaciylates with pendant aryl benzoates. 

More recently, the cyclodextrins became of interest as model enzymes. It was found that they can accelerate different reactions by factors ranging from 0.3 to 400, the factor smaller than 1.0 corresponding to a deceleration [1, 6, 8, 9]. Some of these reactions and the acceleration rates are listed in Table I. The cyclodextrins not only catalyze reactions but they also mimic the reaction mechanism of enzymes as could be demonstrated for the system a-cyclodextrin - aryl benzoate [6]. In this case, benzoyl-a-cyclodextrin was observed as reaction intermediate, in direct analogy to the acylation of the active site during the cleavage of esters through a-chymotrypsin. It is not surprising that the acceleration rate of cyclodextrins of maximum 400 is modest as compared to the 10 found for catalysis with a-chymotrypsin as in one... 

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