Study On The Photoredox-Catalyzed Multicomponent Cyclization Of 2-Vinyl Phenols,N-Alkoxypyridinium Salts,and Sulfur Ylides

2,3-dihydrobenzofuran is a common fragment in many natural and artificially synthesized molecule and synthetic chemists have developed numerous different synthetic approaches for accessing structurally diverse dihydrobenzofuran.The majority of these strategies typically involve diverse precursors or key intermediates via nucleophilic or electrophilic pathways.In contrast,an alternative disconnection strategy involving radical-mediated multicomponent reactions for the synthesis of dihydrobenzofurans is attractive but still less explored.N-functionalized pyridinium salts have been widely used in reactions involving free radicals as a kind of free radical precursors.In this paper,2-vinylphenols,N-functionalized pyridinium salt and sulfur ylide are used and it provides a new method for the construction of 2,3-dihydrobenzofuran compounds.In this paper,we used the three components of 2-vinylphenols,N-alkoxypyridine salt and sulfur ylides and through a series of conditions to determine the optimal conditions for the reaction:at room temperature and 7 W blue LEDs,CF3CH2OH as the solvent,Ru(bpy)3Cl2·6H2O as the photocatalyst,CuI as the Lewis acid,1,10-phenanthroline as the ligand,DABCO as the base,when the equivalent ratio of 2-vinylphenol,N-methoxypyridine and sulfur ylide is 1:6:3,the optimal result of 74%1H NMR yield and 69%separation yield can be obtained.Then,the compatibility of the substrate was investigated,a series of 2,3-benzodibenzodialdehydes were synthesized with the separation yield of 31-69%.All the target compounds were characterized by 1H NMR,13C NMR,19F NMR,HRMS.The spectral properties of the target compounds were studied and their spectral data were assigned and identified.It’s worth noting that we used the "flow reaction" to improve the conversion efficiency of some of the substrates in the reaction that did not work well.In addition,by doing a series of mechanism verification experiments,such as free radical trapping experiments and EPR experiments to explore its reaction mechanism.The above research results were published in《ChemCatChem》.