Decay kinetics and products of transformation of aromatic nitroso oxides 4-R–CH–CH–CHNOO, R = OH, NHCOCH

The optical properties and kinetics of consumption of cis- and trans-isomers of aromatic nitroso oxides 4-R–CH–CH–CHNOO (R = OH, NHCOCH) were studied using pulse photolysis and UV-Vis spectrophotometry. The cis-isomer ArNOO is irreversibly transformed into a nitrile oxide intermediate, which then either participates in the (3 + 2)-cycloaddition reaction to the solvent - acetonitrile, or undergoes intramolecular ipso-ortho-cyclization. The substituent R has virtually no effect on the spectral and kinetic characteristics of ArNOO, but shifts the competition between two product formation channels towards ipso-ortho-transformation, leading to the formation of tricyclic isoxazole. Using DFT calculations in the M06L/6-311+G(d,p) + IEFPCM approximation, the details of the mechanisms of the studied transformations are discussed.