Harnessing visible light for metal-free trifluoromethylation/cyclization of unactivated alkenes
Xiaowen Qin1, Chenwei Liu1, Weiheng Yuan1
1School of Pharmacy, Jiangsu University, Zhenjiang 212013, P. R. China. zhiping_yin@ujs.edu.cn.
Abstract:
Visible light-driven radical trifluoromethylation/cyclization of unactivated alkenes offers a sustainable alternative to conventional methods for constructing chroman-4-one and related heterocyclic scaffolds. Herein, we report a metal-free photocatalytic system utilizing rhodamine B as an organic photocatalyst and Togni II reagent as a trifluoromethyl source. This mild protocol enables efficient intramolecular tandem cyclization, affording diverse chroman-4-ones, dihydroquinolin-4-ones, and 1-indanones (24-69% yields) with broad functional group tolerance. The operational simplicity and avoidance of transition metals highlight the synthetic utility of this approach.
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