Recent advances in the use of chiral manganese(I) complexes in asymmetric catalysis are reviewed with particular emphasis on their application in (transfer) hydrogenation of C=O and C=N bonds as well as hydroamination and hydrophosphination of C=C bonds. Mechanistic developments are also summarized along with a future outlook on the field.

Abstract

Direct asymmetric hydrogenation (AH) and asymmetric transfer hydrogenation (ATH) are among the most efficient approaches to produce chiral building blocks. Recently, these types of transformations have witnessed a shift towards the use of molecular catalysts based on earth-abundant transition metals due to their ready availability, economic advantage, and novel properties. With particular regard to manganese, catalyst development has seen both the efficiency and substrate scope in AH and ATH greatly improved, with the emergence of a large number of well-defined Mn-complexes employed in this field. The reaction scope includes the AH and ATH of C=O bonds, asymmetric reduction of C=N bonds and the asymmetric reductive transformations of C=C bonds. Herein, our survey of the area focuses on the catalytic activity of such complexes, their versatility towards asymmetric transformations and the routes employed to convert substrates to their target molecules. We consider the collected findings of this article will be helpful to the reader by providing an insight into ligand design, thereby aiding future catalyst development. Moreover, this review is aimed at highlighting the remarkable progress made in the last seven years in the development of manganese complexes for enantioselective reduction.