A General and Nonempirical Approach to the Determination of the Absolute Configuration of 1-Aryl-1,2-diols

We describe herein a simple, general, and reliable nonempirical approach, based on the exciton coupling method, to assign the absolute configuration of the benzylic stereogenic center of 1-aryl- 1,2-diols. According to this method, it is only necessary to prepare the 4-biphenylboronic esters of the diols and to record their CD spectra in the 230-300 nm range, i.e., in the range corresponding to the long-axis 1La transition of the biphenyl chromophore. From the sign of the CD couplet or Cotton effect at 260 nm it is possible to know the chirality defined by the aryl and biphenyl chromophore transitions and then to determine the absolute configuration of the benzylic carbon. By this approach, simple rules have been formulated which allow us to establish the absolute configuration of many classes of 1-aryl-1,2-diols.