Visible-Light-Induced Alkoxyl Radicals Enable α-C(sp3)-H Bond Allylation

Jing Zhang; Dan Liu; Song Liu; Yuanyuan Ge; Yu Lan; Yiyun Chen

doi:10.1016/j.isci.2019.100755

Visible-Light-Induced Alkoxyl Radicals Enable α-C(sp³)-H Bond Allylation

iScience. 2020 Jan 24;23(1):100755. doi: 10.1016/j.isci.2019.100755. Epub 2019 Dec 4.

Authors

Jing Zhang¹, Dan Liu¹, Song Liu², Yuanyuan Ge¹, Yu Lan³, Yiyun Chen⁴

Affiliations

¹ State Key Laboratory of Bioorganic and Natural Products Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China.
² School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030, China.
³ School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030, China; Green Catalysis Center, College of Chemistry, Zhengzhou University, Zhengzhou, Henan 450001, China. Electronic address: lanyu@cqu.edu.cn.
⁴ State Key Laboratory of Bioorganic and Natural Products Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China. Electronic address: yiyunchen@sioc.ac.cn.

Abstract

The alkoxyl radical is an essential reactive intermediate in mechanistic studies and organic synthesis with hydrogen atom transfer (HAT) reactivity. However, compared with intramolecular 1,5-HAT or intermolecular HAT of alkoxyl radicals, the intramolecular 1,2-HAT reactivity has been limited to theoretical studies and rarely synthetically utilized. Here we report the first selective 1,2-HAT of alkoxyl radicals for α-C(sp³)-H bond allylation of α-carbonyl, α-cyano, α-trifluoromethyl, and benzylic N-alkoxylphthalimides. The mechanistic probing experiments, electron paramagnetic resonance (EPR) studies, and density functional theory (DFT) calculations confirmed the 1,2-HAT reactivity of alkoxyl radicals, and the use of protic solvents lowered the activation energy by up to 10.4 kcal/mol to facilitate the α-C(sp³)-H allylation reaction.

Keywords: Organic Chemistry; Organic Reaction; Physical Organic Chemistry.