NOVELTY - 4-Bromobenzaldehyde, 3-amino-propanol and water are added to reaction flask, stirred, N-bromo-succinamide is added, heated, completely dissolved, reacted, quenched, extracted, organic phase is separated, dried, solvent is removed, and purified, to obtain 2-(4-bromophenyl)-1,3-oxazine. 2-(4-bromophenyl)-1,3-oxazine, triisopropyl borate and anhydrous tetrahydrofuran are added to reaction flask, stirred, cooled, n-butyllithium is dripped, heated, quenched, organic phase is separated, solvent is evaporated, and rinsed, to obtain 4-(1,3-oxazin-2-yl)phenylboronic acid as white solid.    USE - Preparation of 4-(1,3-oxazin-2-yl)phenylboronic acid used as pharmaceutical intermediate and organic chemical reagents (all claimed).    ADVANTAGE - The method enables environmentally-friendly, economical and simple preparation of 4-(1,3-oxazin-2-yl)phenylboronic acid having excellent storage stability, with high yield and purity.    DETAILED DESCRIPTION - 1 eq 4-Bromobenzaldehyde, 1.2 eq 3-amino-propanol and water are added to 3 L reaction flask, stirred at room temperature for 20 minutes, 1.2 eq N-bromo-succinamide is added, heated at 70 degrees C, completely dissolved, reacted for 3 hours, quenched with sodium hydroxide solution having concentration of 20%, extracted with ethyl acetate, organic phase is separated, dried, solvent is removed, and purified by silica gel column chromatography with ethyl acetate and petroleum ether in ratio of 2:3, to obtain 2-(4-bromophenyl)-1,3-oxazine as white solid. 1 eq 2-(4-bromophenyl)-1,3-oxazine, 1 eq triisopropyl borate and anhydrous tetrahydrofuran are added to 3 L reaction flask, stirred, cooled to -78 degrees C, 1.05 eq n-butyllithium is dripped, heated at room temperature for 12 hours, quenched with ammonium chloride solution, organic phase is separated, aqueous phase is extracted with ethyl acetate, washed, dried, solvent is evaporated under reduced pressure, and rinsed with n-hexane, to obtain 4-(1,3-oxazin-2-yl)phenylboronic acid as white solid.