Non--Symmetric Chiral-at-Ruthenium Catalyst for Highly Efficient Enantioselective Intramolecular C(sp)-H Amidation.

Author(s) Zhou, Z.; Chen, S.; Hong, Y.; Winterling, E.; Tan, Y.; Hemming, M.; Harms, K.; Houk, K.N.; Meggers, E.
Journal J Am Chem Soc
Date Published 2019 Nov 21
Abstract

A new class of chiral ruthenium catalysts is introduced in which ruthenium is cyclometalated by two 7-methyl-1,7-phenanthrolinium heterocycles, resulting in chelating pyridylidene remote N-heterocyclic carbene ligands (rNHCs). The overall chirality results from a stereogenic metal center featuring either a Λ or Δ absolute configuration. This work features the importance of the relative metal-centered stereochemistry. Only the non--symmetric chiral-at-ruthenium complexes display unprecedented catalytic activity for the intramolecular C(sp)-H amidation of 1,4,2-dioxazol-5-ones to provide chiral γ-lactams with up to 99:1 er and catalyst loadings down to 0.005 mol % (up to 11 200 TON), while the -symmetric diastereomer favors an undesired Curtius-type rearrangement. DFT calculations elucidate the origins of the superior C-H amidation reactivity displayed by the non--symmetric catalysts compared to related -symmetric counterparts.

DOI 10.1021/jacs.9b09301
ISSN 1520-5126
Citation Zhou Z, Chen S, Hong Y, Winterling E, Tan Y, Hemming M, et al. Non--Symmetric Chiral-at-Ruthenium Catalyst for Highly Efficient Enantioselective Intramolecular C(sp)-H Amidation. J Am Chem Soc. 2019.

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