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

Rui FuMengyu XuYujing WangXin-Xin WuXiao-Guang Bao
Published in: Angewandte Chemie (International ed. in English) (2024)
The construction of C(sp 3 )-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 3 HE* could lead to a homolytic cleavage of C 4 -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.
Keyphrases
  • visible light
  • energy transfer
  • highly efficient
  • high efficiency
  • quantum dots
  • electron transfer
  • randomized controlled trial
  • radiation therapy
  • radiation induced
  • molecular dynamics