Thioamide-Directed Cobalt(III)-Catalyzed Selective Amidation of C(sp3)-H Bonds

A mild, oxidant-free, and selective Cp*Co-III-catalyzed amidation of thioamides with robust dioxazolone amidating agents via C(sp(3))-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 Cp*Co-III-catalyzed conditions. The observed regioselectivity towards primary C(sp(3))-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-III-catalyzed C(sp(3))-H functionalization and the first to exploit thioamides.