Deoxygenative Tri- and Difluoromethylthiolation of Carboxylic Acids with Benzothiazolium Reagents

Deoxygenative syntheses of fluorinated thioesters directly from carboxylic acids have been developed employing benzothiazolium reagents. The process using BT-SCF₃ represents an attractive approach toward these SCF₃-containing compounds that avoids the use of metal ^-SCF₃ salts or preactivated acyl electrophiles. Moreover, the in situ activation of BT-SCF₂H allows for an unprecedented nucleophilic difluoromethylthiolation reaction. DFT calculations support a mechanistic scenario involving a four-membered transition state where acyl substitution occurs without the formation of an unstable free ^-SCF₂H anion.