Synthesis of 4-(Trifluoromethyl)cyclopentenones and 2-(Trifluoromethyl)furans by Reductive Trifluoroacetylation of Ynones.

Reductive introduction of a fluorine-containing carbon block to readily available conjugated ynones, followed by intramolecular cyclization, successfully gave the corresponding trifluoromethylated cyclopentenones or trifluoromethylated furans in good yields through a simple two-step protocol. The key compound in carbon-carbon bond formation by magnesium-promoted reduction is ethyl trifluoroacetate, which has been rarely used as a fluorine-containing carbon source, especially to electron-deficient carbon atoms in organic synthesis.