Jin Li, Z. Ji, Haiming Wang, Xiaoping Hu, Xiaohan Lu, Tanyu Cheng, Guohua Liu, Rui Liu
Herein, we demonstrated that commercially available and inexpensive triphenylamine (NPh 3 ) could act as an electron donor to form electron donor–acceptor (EDA) complexes with pyridinium-masked enols. Upon irradiation with blue light (455 nm), this in situ formed EDA complex was activated to provide the α-carbonyl radical through N–O bond cleavage, serving as the radical precursor in the formal [4 + 2] cycloaddition with unactivated olefins. A series of pyridinium-masked enols and functionalized olefins were examined under optimized conditions. Mechanistic studies revealed that α-carbon radical and γ-carbonyl radical intermediates are involved during this catalytic process.