Mechanistic Studies on α-Trifluoromethylation of Ketones via Silyl Enol Ethers and Its Application to Other Carbonyl Compounds

Synthesis of α-CF₃ carbonyl compounds has been recognized to be difficult up to now because the polarization of CF₃^δ−-I^δ+ is opposite to that of CH₃^δ+-I^δ−, and this makes it difficult to introduce CF₃⁺ unit to enolates. We recently reported an effective α-trifluoromethylation of ketones by using Et₂Zn with Rh catalyst, but the mechanism has not fully been cleared. Now, we carried out the detailed mechanistic studies and found the involvement of a highly reactive alkylrhodium complex which derived from Et₂Zn and RhCl(PPh₃)₃ in this α-trifluoromethylation. Furthermore, this α-trifluoromethylation was applied to other types of carbonyl compounds in good yields.