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

Abstract

AbstractRuthenium‐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.