A kinetic study of the 1,3-cycloaddition of benzonitrile oxides to para-substituted β-aminocinnamonitriles

Abstract

Stable arylnitrile oxides undergo 1,3-cycloaddition to β-aminocinnamonitriles at the CN or the CC bond, which gives rise to 3,5-disubstituted 1,2,4-oxadiazoles or 3,5-diaryl-4-cyanoisoxazoles, respectively, by parallel reactions in different solvents. Overall kinetics were measured at temperatures in the range 50–90 °C; product selectivities were determined by HPLC rate coefficients for the parallel reactions were, thus, obtained. Rates were enhanced by increasing the solvent polarity. Hammett plots for substitution on the nitrile oxide benzene ring were V-shaped; those for substitution on the enaminonitrile benzene ring had negative ρ-values.