31P NMR Based Method for Determining Enantiopurity of Chiral Phosphoric Acids and Its Application to the BINOL- and H8-BINOL-Based Chiral Phosphoric Acid Thermal Racemization Studies

Abstract

A simple and reliable protocol for determining the enantiopurity of 3,3′-substituted BINOL- and H8-BINOL-based chiral phosphoric acids (CPA) using 31P NMR spectroscopy in the presence of chiral amines as the discriminating agents is described. The generality of this method is demonstrated using nine common BINOL- and H8-BINOL-based chiral acids. This technique was utilized for monitoring the extent of racemization of 3,5-(F3C)2C6H3-substituted BINOL- and H8-BINOL-based CPA at 200, 220, and 250 °C.