Protodeboronation of ortho- and para-Phenol Boronic Acids and Application to ortho and meta Functionalization of Phenols Using Boronic Acids as Blocking and Directing Groups

The first metal-free thermal protodeboronation of ortho- and para-phenol boronic acids in DMSO was developed. The protodeboronation was successfully applied to the synthesis of ortho- and meta-functionalized phenols using the boronic acid moiety as a blocking group and a directing group, respectively. Mechanistic studies suggested that this protodeboronation proceeds through the coordination of water to the boron atom followed by σ-bond metathesis.