Pentafluorobenzyl ethers, preparation

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)... 

Pentafluorobenzyl bromide 2.16.3 Preparation of pentafluorobenzyl ethers and esters for ECD-GLC and MS analysis N-alkylalion of barbiturates 11381 and sulfonamides 1126] ... 

CAUTION Pentafluorobenzyl bromide is a strong lachrymator and should be handled with appropriate precautions for routine work, a stock solution of the reagent in acetone (1 50, w/v) may be prepared [127], An alternative reagent for the purposes just described is hexafluorobenzene. Under the conditions of procedure 2.6, it readily converted free hydroxyl groups into pentafluorophenyl ethers [130],... 

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