Rapid and Slow Generation of 1‐Trifluoromethylvinyllithium: Syntheses and Applications of CF3‐Containing Allylic Alcohols,Allylic Amines,and Vinyl Ketones

1‐(Trifluoromethyl)vinylation is accomplished in two protocols by the in situ generation of thermally unstable 3,3,3‐trifluoroprop‐1‐en‐2‐yllithium ( 1 ): 1) a rapid lithium–halogen‐exchange reaction of 2‐bromo‐3,3,3‐trifluoroprop‐1‐ene ( 2 ) takes effect with sec‐BuLi at ?105 °C to generate vinyllithium 1 , which reacts with more reactive electrophiles, such as aldehydes and N‐tosylimines before its decomposition, to afford 2‐(trifluoromethyl)allyl alcohols and N‐[2‐(trifluoromethyl)allyl] sulfoamides in good yield; 2) treatment of 2 with nBuLi at ?100 °C causes a slow lithium–halogen exchange of 2 , which gives rise to a mixture of 1 and nBuLi. Vinyllithium 1 is preferentially trapped with less reactive electrophiles, such as N,N‐dimethylamides in the presence of BF₃?OEt₂, to afford 1‐(trifluoromethyl)vinyl ketones in good yield. Versatility of the products toward syntheses of CF₃‐containing ring‐fused cyclopentenones is also demonstrated by the Pauson–Khand reaction and the Nazarov cyclization.