A Photoredox/Cobalt-Catalyzed Phosphinyloxy Radical Addition/Cyclization Cascade:Synthesis Of Phosphaisocoumarins

Organophosphorus compounds are of great importance not only in many functional materials and bioactive fine chemicals,such as agrochemicals,pharmaceuticals and natural products,but also as synthetic reagents in organic synthesis,versatile phosphine ligands in transition metal catalysis or nucleophilic organo-catalysts.Phosphaisocoumarin,as phosphorus analog of isocoumarin,displays various potential biological activities.Therefore,the new synthetic methodology of phosphaisocoumarins attracts more and more interests of organic synthetic chemists.In this thesis,we developed a photoredox/cobalt-catalyzed dual catalytic system to for the synthesis of phosphaisocoumarin compounds.Initially,diphenylphosphinic acid and diphenylacetylene were chosen as the model substrates,a series of conditions(such as base,solvent,photocatalyst,cobalt catalyst were evaluated,the optimal reaction conditions were as follows:cesium fluoride as a base,chloroform/water as a solvent,Acr+-MesClO4-(6 mol%in portion)as a photocatalyst,[Co(dmgH)2]PyCl(8 mol%)as a cobalt catalyst.A series of substituted phosphaisocoumarin compounds(24 examples)were obtained by expanding the range of substrates.Meanwhile,we have studied the reaction mechanism(such as free radical trapping experiment,Stern-Volmer emission quenching studies,etc.)and proposed a possible reaction mechanism.(?)All the desired products were characterized by 1H NMR,13C NMR,31P NMR,HRMS,IR and the spectroscopic properties of the target compounds were studied.