Influence of the diol structure on the Lewis acidity of phenylboronates

摘要

A series of cyclic esters of pentafluorophenylboronic acid have been obtained and their Lewis acidity evaluated experimentally by a modified Gutmann method. The results based on ~(31)P NMR measurements were compared with those determined by quantum mechanical calculations at the DFT-VSXC/pcS-2 level of theory. The differences in Lewis acidity are discussed on the basis of electronic and geometric parameters. The calculations revealed that the complexes of investigated esters with Et_3PO have multiple conformers of a wide range of calculated ~(31)P NMR shielding constants. Additionally, a correlation between the calculated O-B-O angle of esters and the experimental acceptor number was found.