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

Abstract 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 n BuLi at −100 °C causes a slow lithium–halogen exchange of 2 , which gives rise to a mixture of 1 and n BuLi. Vinyllithium 1 is preferentially trapped with less reactive electrophiles, such as N , N ‐dimethylamides in the presence of BF 3 ⋅OEt 2 , to afford 1‐(trifluoromethyl)vinyl ketones in good yield. Versatility of the products toward syntheses of CF 3 ‐containing ring‐fused cyclopentenones is also demonstrated by the Pauson–Khand reaction and the Nazarov cyclization.