Study on the reactions of ethyl 4,4,4-trifluoro-3-oxobutanoate with arylidenemalononitriles

In the presence of a catalytic amount of NEt3, ethyl 4,4,4-trifluoro-3-oxobutanoate reacted readily with arylidenemalononitriles in ethanol at room temperature. It gave two products 2-trifluoromethyl-3,4-dihydro-2H-pyran derivatives and 2-(trifluoromethyl)piperidine derivatives , the ratio of and was depended on the substrates and reaction solvents. Reflux of the ethanol solution of with a catalytic amount of NEt3 afforded 2-trifluoromethyl-1,4,5,6-tetrahydropyridine derivatives in moderate to good yields. The structures of new compounds , and were determined by spectral methods, microanalysis and X-ray diffraction analysis. A possible reaction mechanism for the formation of , and was presented.