Asymmetric Reduction of Ketones by Phosphoric Acid Derived Catalysts

摘要

Enantioenriched secondary alcohols represent an important class of molecules found in numerous intermediates, chiral building blocks, and biologically active compounds. Asymmetric reduction of prochiral ketones constitutes the most straightforward way to form these important moieties. Traditionally, stoichiometric amounts of chiral ligands were used together with an aluminium or a boron hydride to achieve high levels of enantioselectivity. Various catalytic processes have been developed in the past three decades in an effort to eliminate the use of stoichiometric amounts of chiral regents. The Corey-Bakshi-Shibata (CBS) catalyst and Noyori's ruthenium catalyst represent two of the most well-known methods for this purpose. Both catalytic systems have been further developed by altering the ligand or by employing different metals in efforts to enhance the selectivity or improve practicality.Despite extensive research, the utilization of simple chiral Br0nsted acids as precatalysts for this asymmetric process is still unknown.