Long-wavelength Fluorogenic Derivatization of Aryl Halides Based on the Formation of Stilbene by Heck Reaction with Vinylbenzenes.

The long-wavelength fluorogenic derivatization method for aryl halides was developed based on stilbene formation by the Heck coupling reaction between aryl halides and vinylbenzenes in the presence of palladium(II) acetate as a catalyst. Fluorescent maximum wavelengths of the derivative obtained by the proposed reaction were 365 - 450 nm, which were 50 - 100 nm longer than those of the biphenyl derivatives formed with our previously developed fluorogenic derivatization method. Also, by the investigation using vinylbenzenes containing electron-donating or -withdrawing functional groups, it was found that an internal charge transfer system could contribute to extend the emission wavelength of the derivative. Furthermore, the proposed reaction was applied to develop a pre-column derivatization HPLC with fluorescence detection method for aryl bromides using 4-vinylanisole. p-Substituted aryl bromide derivatives (i.e., p-bromobenzonitrile, p-bromoanisole, bromobenzene, p-bromobenzoic acid ethyl ester, p-bromotoluene) were successfully detected within 40 min with the detection limit of 0.007 - 0.264 μM. Despite the short reaction time of 10 min, the reaction yields for p-bromoanisole and bromobenzene were good at 101 and 87%, respectively.