Cobalt-Catalyzed Ortho -C(sp 2 )-H Amidation of Benzaldehydes with Dioxazolones Using Transient Directing Groups.

An efficient and convenient cobalt-catalyzed ortho -C(sp ² )-H amidation of benzaldehydes employing dioxazolones as the aminating reagent has been developed. The key feature of this protocol is the use of green and economic earth-abundant metals cobalt as the catalyst with the p -chloroaniline as the transient directing group. Further application of our approach was demonstrated by the synthesis of C1r serine protease inhibitor 45 and elastase inhibitor 49 .