Studies On The Transition-metal-free Light-mediated Trifluoromethylation Reaction Of Coumarins

Photo-catalyzed trifluoromethylation of coumarins and photo-catalyzed iodocyclization of N?arylpropynamides mediated by hypervalent iodine reagent have been investigated in this thesis.Section one focuses on photo-catalyzed trifluoromethylation of coumarins with CF₃SO₂Na.Trifluoromethylated coumarins are important fundamental building block of the pharmaceutical molecules,thus the synthetic methodology of trifluoromethylated coumarins is of great significance.The general methods with no light introducing trifluoromethyl group usually need oxidizing agent in hard reaction conditions;while the methods with light almost need photosensitizer to harvest resonant photons.Most of the photosensitizers are transition metals,harmful and expensive.Therefore,the development on trifluoromethylation with mild reacting condition,good tolerance of functional groups and without using transition metals photosensitizer has important significance in methodology and industrial value.With coumarins as main objects,screening the trifluoromethylating reagent,solvents and bases,we determined the optimal reaction conditions:4.0 equiv CF₃SO₂Na,4.0 equiv K₂HPO₄and acetone as solvent at room temperature in the atmosphere of Ar for 12 h.This method has the advantages of mild condition and good tolerance for functional groups.Section two focuses on the photo-catalyzed iodocyclization of N?arylpropynamides mediated by hypervalent iodine reagent.Halogen cyclization reactions are usually electrophilic additions,we use light afford a radical reaction process.With N?arylpropynamides as main objects,after screening the superiodine reagent,solvents,bases,the optimal reaction conditions was obtained:2.0 equiv NaOAc,acetonitrile,at room temperature in the atmosphere of O2 for 18 h.With the optimal conditons in hand,we investigated the scope of substrate preliminarily and explored the effects of functional groups to the reaction yield.