A synthesis of γ-trifluoromethyl α,β-unsaturated γ-butyrolactones using CF₃SiMe₃ as a trifluoromethylating agent

A general synthesis of γ-trifluoromethyl α,β-unsaturated γ-butyrolactones is described. The fluoride-catalyzed nucleophilic addition of a trifluoromethyl (CF₃) group generated from (trifluoromethyl)trimethylsilane (CF₃SiMe₃, Ruppert-Prakash reagent) to a masked maleic anhydride 1 (cyclopentadiene-maleic anhydride adduct) provides the corresponding adducts 2 with high stereoselectivity. The γ-trifluoromethyl α,β-unsaturated γ-butyrolactones 4 were obtained after treatment of the adducts 2 with Grignard reagents, followed by flash-vacuum pyrolysis.