Alpha-trifluoromethylation of secondary and sterically hindered carboxylates with use of BrF3.

Secondary esters and those with sterical hindrance at the beta carbon were reacted with base, carbon disulfide, and methyl iodide to produce methyl 2-carboalkoxydithioalkenoate (2). These compounds were reacted with BrF(3), forming the corresponding alpha-trifluoromethyl esters (3) along with 1,1-difluoro-2-trifluoromethyl-2-alkyl ethers (4). The products of type 4 have been transformed to derivatives of type 3, thus raising the overall yields of the target respective alpha-trifluoromethyl esters to 65-80%. The reaction is tolerant to different functional groups such as halogens, protected alcohols, esters, and lactones.