On treatment with sec-BuLi at -105 degrees C, 2-bromo-3,3,3-trifluoropropene undergoes rapid lithium-halogen exchange to generate thermally unstable 1-(trifluoromethyl)vinyllithium, which reacts with N-tosylimines to afford N-[2-(trifluoromethyl)allyl]amides in high yield. Propargylation of the amides, followed by the Pauson-Khand reaction, readily provides pyrrolidine ring-fused cyclopentenones with an angular trifluoromethyl group.