E , Z -Isomers of 3-Ethoxy-4,4,4-trifluorobut-2-enenitrile and N -Methylpyrrolidines Derived from Them

3-Ethoxy-4,4,4-trifluorobut-2-enenitrile was synthesized by the Wittig reaction of ethyl trifluoroacetate and (cyanomethylidene)triphenylphosphorane and was separated to individual E- and Z-isomers by rectification. Each isomer undergoes stereospecific 1,3-dipolar cycloaddition to N-methyl(methaniminio)-N-methylide generated in situ to give E- and Z-isomers of 4-cyano-3-ethoxy-3-trifluoromethyl-1-methylpyrrolidine.