Selective monophosphorylation of cyclic diols and polyols via hemiboronic acid catalysis.

Abstract

The phosphorylation of organic molecules is a biologically essential chemical transformation. Consequently, there is high demand for methods that allow for the direct, selective, and catalytic monophosphorylation of diols and complex polyols. Due to their ability to form reversible covalent bonds with hydroxy (-OH) groups, hemiboronic acids present the unique capacity to catalytically activate diols in a nucleophilic manner. Herein, we disclose a hemiboronic acid-catalyzed monophosphorylation protocol, amenable to a variety of acyclic and cyclic diols, along with the site-selective functionalization of polyols including saccharides. Mechanistic analyses comprising of kinetic experiments and computational investigation were performed to probe for the origin of the observed site-selectivities. We propose that the observed site-selectivity originates from a difference in calculated nucleophilicity between the diol oxygens in the lower energy epimer of the reactive complex, which also exhibits a kinetically stabilizing hydrogen bonding effect with the approaching electrophile.