The Construction Of C(sp~2)-P And C(sp~2)-C(sp~3) Bonds Based On Visible Light Induction

With the concept of atom economy and environmental protection,visible-light-induced reactions have been widely used to construct C-C and C-X(X = O,P,S)bonds.In this thesis,the synthesis of coumarin derivatives based on visible light photocatalysis has been investigated.The detailed results are outlined as follows:1.Regioselective phosphinylation of coumarins under green LED irradiation and its mechanismThe regioselective synthesis of 3-phosphinylated coumarins in moderate to excellent yields was developed via an EY/BPO mediated cross-dehydrogenative coupling(CDC)reaction under green LED irradiation.The results of control experiments showed that the active intermediate,a P-centered radical,might be obtained through energy transfer and electron transfer processes(Scheme 1).2.The mechanism study of radical-mediated 5-exo addition/cyclization of alkynoates with diphenylphosphine oxide promoted by green LEDA metal-free radical-mediated 5-exo addition/cyclization of alkynoates with diphenylphosphine oxide to synthesize the 3-phosphorylated coumarins with a wide range of substrate scope was achieved under visible light.The results of control experiments could prove that in this catalytic system,3-phosphonated coumarins are products,simultaneously serve as additional photosensitizers(Scheme 2).3.A simple approach to indeno-coumarins via visible-light-induced cyclization of aryl alkynoates with diethyl bromomalonateVisible-light-induced triple-domino cyclization between aryl alkynoates and diethyl bromomalonate was developed for the synthesis of indeno-coumarins.This one-pot method substantially simplified the production process for indeno-coumarins and a series of indeno-coumarins could be isolated in moderate to high yields.It was found that the obtained indeno-coumarins could be used as additional photosensitizers to initiate this transformation.A possible radical mechanism accompanying the processes of electron transfer and energy transfer is proposed based on the results of ESI-MS analysis,cyclic voltammetry,Stern–Volmer quenching experiments and control experiments.The photoluminescence properties(emission spectra and quantum yields)of the obtained indeno-coumarins were investigated(Scheme 3).