Abstract

The direct amidation of C–H bonds is a highly desirable reaction owing to the widespread utility of amidated products in total synthesis, medicinal chemistry, and materials science. In this context, we have developed a new mechanistic platform that employs custom-designed transition metal-based catalyst systems in combination with dioxazolones as robust and practical amino sources. This strategy enables the generation of metal-nitrenoid intermediates, ultimately achieving C–H amidation via either inner or outer-sphere C–H activation of insertion pathways. Building on this foundation, we recently introduced transition metal-based catalyst systems for asymmetric C−H amidation, providing an efficient route to synthesize chiral lactams and functional amino compounds from readily available commodity chemicals.

In developing our C-H amination reactions, we also thoroughly investigated the involvement of key nitrenoid intermediates using both experimental and computational mechanistic studies. In fact, we designed a chromophoric octahedral rhodium complex featuring a bidentate dioxazolone ligand, in which photoinduced metal-to-ligand charge transfer initiates catalytic C–H amidation. X-Ray photocrystallographic analysis of Rh-dioxazolone complexes enabled structural characterization of Rh-acylnitrenoid intermediate for the first time and provided definitive evidence that the singlet nitrenoid species is primarily responsible for acylamino transfer process. Furthermore, in crystallo monitoring of the reaction between a nucleophile and the in situ generated Rh-acylnitrenoid established a crystallographically traceable system, capturing the key mechanistic snapshots of nitrenoid transfer.

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