Quantitative Analysis on Two-Point Ligand Modulation of Iridium Catalysts for Chemodivergent C-H Amidation

Abstract

The transition-metal-catalyzed nitrenoid transfer reaction is one of the most attractive methods for installing a new C-N bond into diverse reactive units. While numerous selective aminations are known, understanding complex structural effects of the key intermediates on the observed chemoselectivity is still elusive in most cases. Herein, we report a designing approach to enable selective nitrenoid transfer leading to sp(2) spirocyclization and sp(3) C-H insertion by cooperative two-point modulation of ligands in the (CpIr)-Ir-X(III)(kappa(2)-chelate) catalyst system. Computational analysis led us to interrogate structural motifs that can be attributed to the desired mechanistic dichotomy. Multivariate linear regression analysis on the perturbation on the eta(5)-cyclopentadienyl ancillary (Cp-X) and LX coligand, wherein we prepared over than 40 new catalysts for screening, allowed for construction of an intuitive yet robust statistical model that predicts a large set of chemoselective outcomes, implying that the catalysts' structural effects play a critical role on the chemoselective nitrenoid transfer. On the basis of this quantitative analysis, a new catalytic platform is now established for the unique lactam formation, leading to the unprecedented chemoselective reactivity (up to >20:1) toward a diverse array of competing sites, such as tertiary, secondary, benzylic, allylic C-H bonds, and aromatic pi system.© 2020 American Chemical Society