Borylative Desymmetrization of multifunctional haloarenes assisted by sodium dispersion

Multiply halogenated aromatic compounds were selectively borylated by a boron alkoxide in the presence of sodium dispersion when the reaction was carried out at a low temperature, while multi-functionalization took place at an elevated temperature. The reaction of 1,4-dichlorobenzene with sodium dispersion (200–1200 mol%) in the presence of isopropyloxyboron pinacolate (120–240 mol%) afforded (4-chlorophenyl)boron pinacolate in up to 84% yield. Formation of diborylated product hardly accompanied under the reaction conditions at –78 °C for 1 h.