Oxidative Difluoromethylation of Tetrahydroisoquinolines Using TMSCF2SPh: Synthesis of Fluorinated Pyrrolo[2,1-a]isoquinolines and Benzo[a]quinolizidines

An efficient C 1-difluoromethylation of tetrahydroisoquinolenes was achieved using TMSCF 2 SPh as a difluoromethylating agent and 2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (TEMPO + BF 4 – ) as an oxidant. The process provides an access to a variety of C 1-difluoro(phenylsulfanyl)methylated tetrahydroisoquinoline adducts in good yields. These adducts were employed as key precursors for preparing fluorinated pyrrolo[2,1- a ]isoquinoline and benzo[ a ]quinolizidines.