Facile synthesis of arylboronic esters by palladacycle-catalyzed bromination of 2-arylbenzoxazoles and subsequent borylation of the brominated products

An efficient and facile synthesis of arylboronic esters bearing the benzoxazole moiety has been described using a new family of palladacycle: cyclopalladated ferrocenylimines as the catalysts. This reaction includes two concessive steps: bromination of 2-arylbenzoxazoles and subsequent borylation. The bromination of para-C-H bond was an electrophilic substitution process by using NBS as the brominating reagent, and the brominated products were determined by HMBC (1H-detected heteronuclear multiple bond correlation) spectra. Particularly, the borylation step could be carried out successively only after removal of the solvent to afford the arylboronic esters in moderate to good yields.