Cooperative Phosphine-Photoredox Catalysis Enables N–H Activation of Azoles for Intermolecular Olefin Hydroamination

Abstract

Catalytic intermolecular olefin hydroamination is an enabling synthetic strategy that offers direct and atom-economical access to a variety of nitrogen-containing compounds from abundant feedstocks. However, despite numerous advances in catalyst design and reaction development, hydroamination of N−H azoles with unactivated olefins remains an unsolved problem in synthesis. We report a dual phosphine and photoredox catalytic protocol for the hydroamination of numerous structurally diverse and medicinally relevant N−H azoles with unactivated olefins. Hydroamination proceeds with high anti-Markovnikov regioselectivity and N-site selectivity. The mild conditions and high functional group tolerance of the reaction permit the rapid construction of molecular complexity and late-stage functionalization of bioactive compounds. N−H bond activation is proposed to proceed via polar addition of the N−H azole to a phosphine radical cation, followed by P−N α-scission from a phosphoranyl radical intermediate. Reactivity and N-site selectivity are classified by azole N−H BDFE and nitrogen-centered radical spin density, respectively, which can serve as a useful predictive aid in extending the reaction to unseen azoles.