Selective electrochemical synthesis and reactivity of functional benzylic fluorosilylsynthons

Electrochemical reductive silylation of meta-(trifluoromethyl)arenes by the sacrificial anode technique selectively led to meta-trimethylsilyldifluoromethylarenes (ArCF2TMS), in the presence of an excess of TMSCl and in a THF/cosolvent mixture (cosolvent=DMPU or HMPA). In the case of meta-(trimethylsilyldifluoromethyl)trifluoromethylbenzene, the influence of the cosolvent on the silylation selectivity was studied. A cyclic voltammetry study allowed an explanation of the difference in the results obtained between the trifluoromethylbenzene and meta-bistrifluoromethylbenzene series. ArCF2TMS (Ar=Ph, m-CF3C6H4) species were found efficient for ArCF2-group transfer to diverse electrophiles under Fuchigami’s conditions (KF catalysis in DMF).