Supramolecular Pd Catalyst for the Reduction of Dihydro-β-Carbolines

Significance

In previous work, the authors have described the cyclodextrin(CD)/NaBH₄-induced asymmetric reduction of carbonyl compounds (Tetrahedron Lett. 2008, 49, 4289). Methods for the enantioselective reduction of ketimines have been established, especially Noyori’s asymmetric transfer hydrogenation using Ru(II)-DPEN complexes. In the interest of developing alternative ­approaches, the present paper reports the use of a CD/PdCl₂-Et₃SiH catalytic system for the asymmetric reduction of various dihydro-β-carboline compounds to provide products in excellent yields and enantioselectivities.