1- 4- ethyl pentafluorobenzoate

We have examined the competing isomerization and solvolysis reactions of 1-4-(methylphenyl)ethyl pentafluorobenzoate with two goals in mind (1) We wanted to use the increased sensitivity of modern analytical methods to extend oxygen-18 scrambling studies to mostly aqueous solutions, where we have obtained extensive data for nucleophilic substitution reactions of 1-phenylethyl derivatives. (2) We were interested in comparing the first-order rate constant for internal return of a carbocation-carboxylate anion pair with the corresponding second-order rate constant for the bimolecular combination of the same carbocation with a carboxylate anion, in order to examine the effect of aqueous solvation of free carboxylate anions on their reactivity toward addition to carbocations. 

The j8-diketones C,F5-CO-CH -COR (R = CFj, CjF n-CjF or n-C,Fij) are obtained by Claisen condensation of 2,3,4,5,6-pentafluoro-acetophenone with the appropriate ester RC02Et in the presence of sodium methoxide, and n.m.r. spectroscopy indicates that they are completely enolized in carbon tetrachloride." The reaction between acetophenone and ethyl pentafluorobenzoate in the presence of the catalyst Pr aN MgBr yields both the expected diketone CjFj COCHj-COPh and 5,6,7,8-tetrafluoro-flavone(113a)." ... 

Saloutin et al. reported [138] that the self-condensation of ethyl pentafluorobenzo-ylacetate (271) on refluxing without any catalyst leads to the formation of compound 272 in 37 % yield, acid hydrolysis of which gave 2-pentafluorobenzoyhnethyl-5,6,7,8-tetrafluorochromone (273). Other routes for preparing some new ring-fluorinated chromones have been performed from the 2-ethoxymethylene pentafluorobenzo-ylacetic ester (274) and also via intramolecular cyclization of ethyl pentafluoroben-zoylpyravate (275). The reaction of ester 271 with ethyl orthoformate results in the... 

Ethyl pentafluorobenzoylacetate (33), benzoyl(pentafluorobenzoyl)methane (34), and bis(pentafluorobenzoyl)methane (35) have been synthesized as shown in Scheme 11. The first of these is not a new compound, having been prepared in the early 1960 s by treatment of pentafluorobenzoyl chloride with diethyl malonate in the presence of magnesium ethoxide followed by hydrolysis of the diester CeF8 C0 CH(C02Et)a thus produced, and by condensation of ethyl pentafluorobenzoate with ethyl acetate in the presence... 

Kawahara [156] introduced pentafluorobenzyl esters, prepared by the following procedure. A mixture of four acids (0.8 mg of each) was dissolved in 100 ml of acetone, and 250 mg (25-fold excess) of a-bromo-2,3,4,5,6-pentafluorotoluene and 50 mg (10-fold excess of potassium carbonate were added (it can be replaced with an ethanolic solution of potassium hydroxide). After refluxing for 3 h, the mixture was diluted with 500 ml of diethyl ether and 20 ml of ethyl acetate, washed with 10 ml of water and dried with 8 g of anhydrous sodium sulphate. After filtration, the sulphate and the filter were washed with 50 ml of diethyl ether, the solvent was removed and the residue was dried at 40°C and 50 mmHg it was further dissolved in 100 ml of -hexane and, after an additional 100-fold dilution, 6 /il were injected. The ECD response to pentafluorobenzoate was almost the same as that to aldrin. A method for the preparation of p-substituted benzyl esters of lower monocarboxylic acids on the micro-scale [157] is based on the same reaction scheme. A 10-pl volume of an ethanolic solution of carboxylic acids (ca. 1 pg/pl)... 

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