Carbonate-promoted Photocatalytic Decarboxylative Radical Addition To Aldimine

In recent years,researches on the coupling reaction of photocatalytic decarboxylation of N-hydroxyphthalimide（NHPI） esters to generate radicals and aldimine have made some research achievements.The use of NHPI ester as a radical precursor greatly enriches the scope of application of free radical addition.Although the existing methods have achieved good research results,in most cases,the yield of these methods is less than 80%.In addition,some starting materials are currently not readily available.Therefore,there is an urgent need for a more effective and cheaper method.On the basis of our predecessors,we have developed carbonate-promoted photocatalytic decarboxylation to aldimine radical addition.Our three-year research results are as follows:A photocatalytic decarboxylative coupling of redox-active NHPI esters with aldimines is reported.Broad scope of alkyl radicals generated under visible light irradiation add to glyoxylate-aldimines in good to excellent yields in the presence of Ru（bpy）₃Cl₂,Hantzsch ester（HE）and potassium carbonate.According to the method reported by previous researchers,a series of amino acids can be obtained by cleaving the N-N bond in our product and hydrolyzing the ester group.This method has great potential for application.DFT calculation reveals that negative charged carbonate ion promotes the reaction by facilitating hydrogen atom transfer to the N-centered radical species.In the experiment,we used chenodeoxycholic acid and oleanolic acid NHPI ester to add glyoxylic acid imine to obtain the addition product with excellent yield.Introducing amino acid side chain into carboxyl-containing natural product and drug molecules by this method is demonstrated.