Selective synthesis of α-trifluoromethyl-β-aryl enamines or vinylogous guanidinium salts by treatment of β-halo-β-trifluoromethylstyrenes with secondary amines under different conditions

Unprecedented selective reactions of β-halo-β-trifluoromethylstyrenes with secondary amines under different conditions were discovered. Depending on the electronic properties of the starting styrenes and the reaction parameters, two pathways were found. With neat secondary amines a series of α-trifluoromethyl-β-aryl enamines were prepared in high yields. In contrast, the reactions of the mentioned styrenes with the same amines in polar solvents by substitution of all halogen atoms gave vinylogous guanidinium salts. Possible reaction mechanisms are discussed.