Visible-Light-Induced Oxidation/[3+2]Cycloaddition/Oxidative Aromatization Sequence For The Synthesis Of Pyrrolo[2,1-a]isoquinoline Phosphonates

With the progress of society and the development of economy,the concept of green chemistry has become more and more popular.Therefore,the exploration of a mild and efficient catalytic strategy is favored by chemists.In fact,Phosphorus is the central element of life,whose synthesis and application have very vital research value.At present,modern organophosphorus chemistry has developed into a more mature discipline.The traditional synthesis method of organophosphorus compounds involve relatively harsh reaction conditions such as high temperature,metal catalysts,equivalent wastes and some metal catalysts own bigger toxicity of these defects limits the further application of synthetic phosphorus compounds.So many researchers are working on new ways of synthesis organophosphorus compounds.As an advantageous new catalytic strategy,visible light catalysis is eco-friendly and economic.Consequently,it is of great significance and application value to combine visible light catalysis with synthesis organophosphorus compounds.In this paper,we were using the photocatalytic oxidation/[3+2]cycloaddition/oxidation aromatization strategy to synthesis pyrrolo[2,1-a]isoquinoline phosphonate.We determined the optimal reaction conditions by investigating the photocatalyst,solvent and base.(1)The optimal reaction conditions as follows:mole ratio of substrates(four hydrogen isoquinoline:N-methyl maleicimide)= 1.2:1,1.6 equivalent sodium acetic acid and methylene chloride solvent 3 ml,36W CFL stirring at room temperature for 24 hours,then add NBS stir for 1 hour.(2)After that,we investigated the application range of the substrate of the reaction,and found that both the electronic effect and the steric hindrance effect had no significant influence on the reaction efficiency.(3)The substrate of benzene kun and alkyl ester can be applied to this reaction.(4)At the end of the day,we synthesized 16 kinds of potentially bioactive organophosphorus compounds and the separation up to 85%yield.All the structure of compounds are confirmed by 1H NMR?13C NMR?31P NMR?HRMS?and X-ray.According to the report and experimental results,we proposed the mechanism:First,the visible light and base with imine structure under the effect of 1,3-dipolar,then 1,3-dipolar with different electronic component deficiency in[3 + 2]cycloaddition reaction,the product obtained under the action of NBS further oxidative aromatization with potential biological activity of pyrrole and[2,1-a]isoquinoline phosphonates.