Difluorovinyl -Toluenesulfonate

Preparative Methods the reagent is prepared by the dropwise addition of 2 equiv of n-BuLi to commercially available 2,2,2-trifluoroethyl-p-toluenesulfonate (2) in THF followed by quenching of the resultant anion 3 with H2O/THF (eq 1). The intermediate fluorovinyl lithium anion 3 has also been prepared from 2 by reaction with LDA.  

Reaction of the anion 3 with trialkyl boron compounds gives adducts which eliminate the toluenesulfonate group in a 1,2-alkyl shift (eq 3). The resultant vinyl boron compounds are capable of undergoing Suzuki-type cross-coupling reactions. Using this method, Ichikawa et al. were able to convert 3 into functionalized aryl adducts which were then cyclized in a 5-endo fashion to give monofluorinated adducts.  

Purification purified by silica gel chromatography (hexane EtOAc 10 1).2 

Anion Chemistry. The fluorovinyl anion 3 (eq 1) is a versatile intermediate and can be reacted with a variety of electrophiles. When treated with ketones, the anion gives secondary alcohols which can be sequentially hydrolyzed, firstly to carboxy enol-tosylates under acidic conditions, and then under basic conditions to give synthetically useful a-keto carboxylic acids (eq 2).  

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