Metal-free Photo-Induced Cascade Cyclization of Alkyne-Tethered N-Alkoxylbenzamides

In this work, a photo-induced synthesis of isoxazolidine-fused isoquinolin-1-ones and 3,4-dihydro-[1,2]oxazino[2,3-b]isoquinolin-10(2H)-one from alkyne-tethered N-alkoxybenzamides is reported. The gram-scaled synthesis and structural elaboration of isoxazolidine-fused isoquinolin-1-one are also realized. The reaction is promoted by 1.0 equiv of TBAC, featuring with metal-free and catalyst-free conditions. In the reaction, it is believed that the starting materials alkyne-tethered N-alkoxybenzamides serve as photo-sensitizer, and the photoexcited substrate induces the formation of chloro radical. The N-radical results from hydrogen atom abstraction of chloro radical with N-H bond of substrates.