An Unusual Example of Base-Free Catalyzed Reduction of C═O and C═NR Bonds by Transfer Hydrogenation and Some Useful Implications

Abstract

A series of Cp*IrIII(NHC) complexes have been used in the catalytic transfer hydrogenation of ketones and imines in iPrOH, showing that the reduction of ketones is complete within minutes at room temperature, with the unprecedented feature that the reaction does not need the addition of a base as cocatalyst. This finding implies that aldehydes (a problematic family of substrates for hydrogen transfer) and base-sensitive ketones can be reduced using these catalysts. Furthermore, the catalysts can be utilized in the tandem reduction of chiral aldehydes and their enzymatic dynamic kinetic resolution (DKR), providing moderate asymmetric inductions.