Thioamide-Directed Cobalt(III)-Catalyzed Selective Amidation of C(sp )-H Bonds.

A mild, oxidant-free, and selective CpCo -catalyzed amidation of thioamides with robust dioxazolone amidating agents via C(sp )-H bond activation to generate the desired amidated products is reported. The method is efficient and allows for the C-H amidation of a wide range of functionalized thioamides with aryl-, heteroaryl-, and alkyl-substituted dioxazolones under the CpCo -catalyzed conditions. The observed regioselectivity towards primary C(sp )-H activation is supported by computational studies and the cyclometalation is proposed to proceed by means of an external carboxylate-assisted concerted metalation/deprotonation mechanism. The reported method is a rare example of the use of a directing group other than the commonly used pyridine and quinolone classes for Cp*Co -catalyzed C(sp )-H functionalization and the first to exploit thioamides.