Synthesis and transformations of trifluoromethyl-substituted cyanopyrrolines

3-Cyano-1-methyl-4-trifluoromethyl-3-pyrroline, as well as 4-cyano-1-methyl-3-trifluoromethyl- and 3-cyano-1-methyl-4-trifluoromethyl-2-pyrrolines were synthesized under DBU catalysis by heating of Z-3-cyano-4-ethoxy-1-methyl-4-trifluoromethyl-pyrrolidine in vacuo. 3-Cyano-1-methyl-4-trifluoromethyl-3-pyrroline undergoes redox disproportionation catalyzed by potassium tert-butoxide to form 2,4-bis(2-cyano-1-trifluoromethylprop-2-enylidene)-1,3-dimethyl-1,3-diazetidine and E-/Z-isomers of 3-cyano-1-methyl-4-trifluoromethylpyrrolidine. The same 1,3-diazetidine is formed by oxidation of 3-cyano-1-methyl-4-trifluoromethyl-3-pyrroline with atmospheric oxygen. Individual E- and Z-isomers of 3-cyano-1-methyl-4-trifluoromethylpyrrolidine were obtained by stereospecific 1,3-dipolar cycloaddition of E- and Z-isomers of 4,4,4-trifluorobut-2-enonitrile to N-methyl(methaniminio)-N-methylide generated in situ.