Copper-mediated trifluoromethylation of α-diazo esters with TMSCF₃: The important role of water as a promoter

Copper-mediated trifluoromethylation of α-diazo esters with TMSCF₃ reagent has been developed as a new method to prepare α-trifluoromethyl esters. This trifluoromethylation reaction represents the first example of fluoroalkylation of a non-fluorinated carbene precursor. Water plays an important role in promoting the reaction by activating the "CuCF₃" species prepared from CuI/TMSCF₃/CsF (1.0:1.1:1.1). The scope of this trifluoromethylation reaction is broad, and its efficiency is demonstrated in the synthesis of a variety of aryl-, benzyl-, and alkyl-substituted 3,3,3-trifluoropropanoates.