Fluorescent Probes from Stable Aromatic Nitrile Oxides

Stable aromatic nitrile oxides underwent a 1,3-dipolar cycloaddition reaction with 1-iodo-4-(prop-2-yn-1-yloxy)- benzene to afford the expected isoxazoles in very good yields as single regioisomers. The formation of the 5-substituted isoxazoles is in agreement with frontier orbital theory. The reductive cleavage of the N–O bond followed by complexation with BF3·Et2O afforded the corresponding boron complexes, which were further derivatized with a triple bond for click chemistry applications. The photochemical behavior and the fluorescence properties of the derivatives were investigated and discussed, taking theoretical calculations into consideration.