Unexpected Formation of Polysubstituted 1-Azabutadienes and 1,3-Dioxanes from the Reaction of 3-Fluoroalkyl-3-arylaminoacrylic Acid Esters with Formaldehyde

The reaction of 3-fluoroalkyl-3-arylaminoacrylic acid esters with formaldehyde was described. In
the presence of a catalytic amount of triethylamine, the reaction took place readily in acetonitrile
at 70 °C to give the corresponding 2-fluoroalkyl-1-azabutadienes in good yields. cis-Fluoroalkylated
1,3-dioxanes were obtained predominantly when the aryl ring contained an electron-withdrawing
group and the reaction was carried out at room temperature under catalysis of triethylamine and
tetrabutylammonium bromide. A possible mechanism was proposed.