Boron trifluoride facilitated transesterification of dioxaborolanes

The direct transesterification of dioxaborolanes (alkane-1,2-diol based boronate esters) was explored. Using BF₃·OEt₂, alkane-1,2-diol based mono- and bis-boronate esters (i.e., pinacol and ethylene glycol) have been converted quantitatively to either benzene-1,2-diol or alkane-1,3-diol based boronate esters. In the case of pinacol esters, esterification is facilitated by the accompanying pinacol rearrangement, thus shifting the reaction equilibrium.