Stereoselective synthesis of (Z)-trifluoromethyl enamines and their Lewis acid-mediated conversion into (E)-isomers

(Z)-β-Trifluoromethyl enamines were prepared in high yield stereoselectively by reaction of 2-bromo-3,3,3-trifluoropropene with N-alkyl toluenesulfonamides and potassium t-butoxide in one pot via Michael addition and elimination processes. The (Z)-β-trifluoromethyl enamines could be converted to the corresponding thermodynamically stable (E)-isomers promoted by Lewis acid catalysts at room temperature or thermal isomerization.