Relative reactivities in formation of liquid phenylboronates from 1,2- and 1,3-diols and phenylboronic anhydride

Abstract

It is shown that no dramatic thermodynamic differences exist between phenylboronates of 1,2- and 1,3-diols in regard to their formation in liquid phase from the diol and phenylboronic anhydride. Effects of ring substituents on the reaction are as great as those of ring size. These findings are discussed in relation to the ring-strain hypothesis. Configuration at carbons 2 and 3 of meso- and DL-butane-2,3-diols is retained in the derived esters, confirming exclusive B–O fission as a major pathway in ester formation from these diols. A simple method for the separation of these and other meso- and DL-diol pairs is suggested.