An Atropisomerically Enforced Phosphoric Acid for Organocatalytic Asymmetric Reactions

Abstract

Three BINOL‐derived phosphoric acids exhibiting atropisomerism in the 3,3′‐positions were obtained by Suzuki coupling reaction. The diastereomeric mixture was resolved by HPLC. Structural assignment was achieved by NOE‐NMR analysis and by TD‐DFT simulation of the electronic circular dichroism (ECD) spectra. The three atropisomeric catalysts were tested in three enantioselective reactions, comparing their ability to induce enantioselectivity with related, well‐known, phosphoric acid structures. All three catalysts were competent in promoting the reactions, rendering excellent enantioselectivity (98 % ee) in one case. The atropisomeric features at the 3,3′‐position were indeed found to influence the outcome of the reaction, demonstrating the potential of atropisomeric conformational control at the 3,3′‐position of the BINOL core in the rationalization of catalyst performances and in the design of new efficient structures.