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-trifluoro-prop-1-ene (2) takes effect with sec-BuLi at -105 degrees 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 degrees 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 center dot 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.