Protection of the Benzoxaborole Moiety: Synthesis and Functionalization of Zwitterionic Benzoxaborole Complexes

The synthesis and utility of three benzoxaborole protecting groups are reported. These protecting groups improve organic solubility and allow otherwise incompatible reactions (oxidations, substitutions, and mild reductions) to be achieved in the presence of the benzoxaborole moiety. 3-( N, N-Dimethylamino)-1-propanol was determined to be useful in one-step sequences and is readily cleaved upon workup. Two other groups, N-methylsalicylidenimine and 2-[1-(methylimino)ethyl]phenol, are suitable for multistep syntheses. Deprotection with mild aqueous acid allows for chromatography-free isolation of the benzoxaborole in high yields.