α-trifluoromethylation of secondary and sterically hindered carboxylates with use of BrF₃

Secondary esters and those with sterical hindrance at the β 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 α-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 α-trifluoromethyl esters to 65-80%. The reaction is tolerant to different functional groups such as halogens, protected alcohols, esters, and lactones.