Effect of Boron Trifluoride on the Transesterification of Boronate Esters

Boronate ester-based materials have received interest and found utility in many applications. The preeminent goal of this research is to advance the field of boron-oxygen based porous materials. The formation of these materials has been predominantly facilitated by boron-oxygen dynamic covalent character. In an effort to understand and improve this process, we are investigating the effect of boron trifluoride, a well-known Lewis acid catalyst, on synthesis and exchange of dioxaboroles. From our previous studies, we have observed an increase in reaction rate as well as beneficial side reactions, which have driven the reaction equilibrium to unexpected products from the transesterification of phenyl pinacol boronate ester (PPB) in the presence of boron trifluoride. Initially, we studied the effect of boron trifluoride on the transesterification of different boronate esters (dioxaboroles) with catechol. Then, we synthesized bis boronate ester materials by combining the knowledge learned in the above-described work. Finally, we investigated the Lewis acid-catalyzed (boron trifluoride and para-toluene sulfonic acid) pinacol rearrangement of different diols (pinacol, hydrobenzoin, and benzpinacol). In the presence of boron trifluoride all transesterification reactions of boronate esters with catechol showed an improvement. Additionally, we were able to find a method to isolate catechol boronate ester on the gram scale.