LEWIS ACID MEDIATED FLUORINATIONS OF AROMATIC SUBSTRATES

Direct fluorination of aromatic substrates, PhZ (Z = Cl, CHO, CH(OCH2)2, NO2, CO2CH2CH3, OH, NHCH3, OCH3, CH3), in the presence and absence of BCl3 or AlCl3, has been investigated. For PhCl and PhOH, inclusion of boron trichloride increased the percent conversion and the amount of para product. However, AlCl3 caused an increase in the ortho regioselectivity in the reaction with chlorobenzene. For PhCHO, inclusion of a Lewis acid decreased the percent conversion. In the presence of BCl3, the ethylene glycol acetal of PhCHO gave only ortho and para fluorinated derivatives with improved conversion. PhCO2CH2CH3 was unaffected by the inclusion of Lewis acid while the percentage conversion of PhNO2 increased only slightly. Fluorination of PhNHCH3, PhOCH3, or PhCH3 gave complex reaction mixtures. p-Nitroanisole gave rise to only 2-fluoro-4-nitroanisole in the presence or absence of either Lewis acid.