Close-Shell Reductive Elimination versus Open-Shell Radical Coupling for Site-Selective Ruthenium-Catalyzed C-H Activations by Computation and Experiments

Angew Chem Int Ed Engl. 2023 May 22;62(22):e202302021. doi: 10.1002/anie.202302021. Epub 2023 Apr 19.

Abstract

Ruthenium-catalyzed σ-bond activation-assisted meta-C-H functionalization has emerged as a useful tool to forge distal C-C bonds. However, given the limited number of mechanistic studies, a clear understanding of the origin of the site-selectivity and the complete reaction pattern is not available. Here, we present systematic computational studies on ruthenium-catalyzed C-H functionalization with primary, secondary, tertiary alkyl bromides and aryl bromides. The C-H scission and the C-C formation were carefully examined. Monocyclometalated ruthenium(II) complexes were identified as the active species, which then underwent inner-sphere single electron transfer (ISET) to activate the organic bromides. The site-selectivity results from the competition between the close-shell reductive elimination and the open-shell radical coupling. Based on this mechanistic understanding, a multilinear regression model was built to predict the site-selectivity, which was further validated by experiments.

Keywords: Multi-Linear Regression; Radical Transformation; Regioselectivity; Remote C−H Activation; Ruthenium.