Analytical Sciences

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

Takumi HIGASHIJIMA, Naoya KISHIKAWA, and Naotaka KURODA

Graduate School of Biomedical Sciences, Course of Pharmaceutical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan

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.

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