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

We dedicate this Letter to Professor James D. White on the occasion of his 80th birthday

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.

Key words

chiral phosphoric acid - racemization - enantiopurity - ³¹P NMR

• References and Notes


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