Isolation of Bright Blue Fluorescent Substances from Sonochemical Hydroxylation of Methyl p-Cyanobenzoate

Sonochemical hydroxylation of methyl p-cyanobenzoate (1a) in water gave a bright blue fluorescence, which are mainly ascribed to three new fluorescent compounds, 3-hydroxy, 2,3-and 2,5-dihydroxy derivatives of 1a. Other benzenes substituted with electron-withdrawing groups also gave similar fluorescence from their hydroxylated derivatives. Among the fluorescence substances, methyl 2,5-dihydroxybenzoate was supposed to be applicable for a fluorescent chemosensor.