Cobalt-Catalyzed anti-Markovnikov Hydroamidation of Allenes

Abstract

Allene hydroamidation represents a highly valuable strategy for the synthesis of allylic amides, which are important synthetic intermediates and widely found in pharmaceuticals and bioactive compounds. Despite the considerable progress achieved in allene hydroamination, the corresponding hydroamidation remains largely underdeveloped. Herein, we report a cobalt-catalyzed anti-Markovnikov hydroamidation of allenes using dioxazolones as readily available amidating reagents. This method proceeds under mild reaction conditions and delivers a broad range of structurally diverse E-allylic amides with excellent regioselectivity and stereoselectivity, generally affording products with >20 : 1 rr and >20 : 1 E/Z. The reaction exhibits broad substrate scope and excellent functional-group tolerance, accommodating a variety of electronically diverse allenes and dioxazolones. Beyond its generality, the practical utility of this method is further demonstrated by the late-stage functionalization of complex bioactive molecules, highlighting its potential for application in the rapid diversification of medicinally relevant scaffolds. Notably, the concise synthesis of the NMDA receptor antagonist and its analogues further underscore the synthetic value of this protocol and its promise for the preparation of structurally complex allylic amides-containing compounds. Preliminary mechanistic studies support a catalytic pathway involving allyl-cobalt and cobalt-nitrenoid intermediates, offering mechanistic insights into the transformation.