Organo‐Photocatalytic Anti‐Markovnikov Hydroamidation of Alkenes with Sulfonyl Azides: A Combined Experimental and Computational Study

Abstract

AbstractThe construction of C(sp3)−N bonds via direct N‐centered radical addition with olefins under benign conditions is a desirable but challenging strategy. Herein, we describe an organo‐photocatalytic approach to achieve anti‐Markovnikov alkene hydroamidation with sulfonyl azides in a highly efficient manner under transition‐metal‐free and mild conditions. A broad range of substrates, including both activated and unactivated alkenes, are suitable for this protocol, providing a convenient and practical method to construct sulfonylamide derivatives. A synergistic experimental and computational mechanistic study suggests that the additive, Hantzsch ester (HE), might undergo a triplet‐triplet energy transfer manner to achieve photosensitization by the organo‐photocatalyst under visible light irradiation. Next, the resulted triplet excited state 3HE* could lead to a homolytic cleavage of C4−H bond, which triggers a straightforward H‐atom transfer (HAT) style in converting sulfonyl azide to the corresponding key amidyl radical. Subsequently, the addition of the amidyl radical to alkene followed by HAT from p‐toluenethiol could proceed to afford the desired anti‐Markovnikov hydroamidation product. It is worth noting that mechanistic pathway bifurcation could be possible for this reaction. A feasible radical chain propagation mechanistic pathway is also proposed to rationalize the high efficiency of this reaction.