The Wittig reaction of fluorinated amides: formation of enamine and imine tautomers

Amides 1a–f reacted with phosphorane 3 at room temperature giving a mixture of enamine 4a–f and imine 6a–f tautomers in excellent yields. These tautomers were formed in competing reaction pathways. Silica gel promoted the conversion of 4d into 6d. Amides 1d and 1f reacted with the methyl analogue of phosphorane 3 giving tautomers 11a,b/12a,b. The β-amino acid derivatives, 13a,b, were formed from sodium borohydride reduction of imines 12a,b.