Deracemization of Chiral-at-Ruthenium Catalyst by Diastereoselective Dynamic Resolution

In this work, we introduce an auxiliary-mediated deracemization protocol in the synthesis of a non-C-2-symmetric chiral-at-ruthenium catalyst bearing two cyclometalated 7-methyl-1,7-phenanthrolinium heterocycles, a CO ligand, and an additional labile MeCN ligand. Upon coordination of a monodentate chiral oxazoline ligand as chiral auxiliary, the racemic complex mixture is transformed into a single diastereomer in quantitative yield via a diastereoselective dynamic resolution process. After removal of the oxazoline ligand under acidic conditions, enantiomerically pure complexes (>20:1 er) with a Delta- and Lambda-configuration were obtained. An application of the chiral-at-ruthenium catalyst to an enantioselective ring-closing C(sp(3))-H amidation of a 1,2,4-dioxazol-5-one to the corresponding chiral gamma-lactam is demonstrated.

Automated summary

In this work, an auxiliary-mediated deracemization protocol was introduced for the synthesis of a non-C-2-symmetric chiral-at-ruthenium catalyst, which was then applied to an enantioselective ring-closing reaction.