Visible Light Promoted Intramolecular Cyclization Reaction Of 2-phenylbenzylienemalononitrile And 2-phenylbenzaldehyde

Visible light-promoted organic reaction has become one of the hotspots of organic chemistry research.Compared with traditional organic reaction,visible light-promoted organic reaction has advantages of simple condition,environment-friendly protocol,good functional-group tolerance,excellent yields of products and so on.In recent years,visible light-promoted carbon-hydrogen bond activation and functionalization reactions have attracted much attention of chemists,and a series of organic reactions based on carbon-hydrogen bond activation have been successfully developed,which can efficiently construct polycyclic compounds.This work mainly focused on the construction of dense ring compounds in series organic reactions based on free radical process promoted by visible light,and carry out the following two studies:（1）By using 2,4,5,6-tetrakis（9-carbazolyl）isophthalonitrile（4Cz IPN）as photocatalyst,a simple and effective method for synthesizing phenanthrene-9,9（10H）dicarbonitrile by intramolecular hydrogen transfer reaction and intramolecular cyclization reaction of 2-phenylbenzylidenemalononitrile under metal-free conditions was developed.Firstly,the optimal reaction conditions were obtained by reaction conditions optimization.Then,28 compounds were obtained in68-97%yield under the optimal reaction conditions.The molecular structure was determined by ¹H NMR,¹³C NMR spectrum and HRMS of all the products and X-ray of three products.In addition,the reaction mechanism was explored by free radical quenching experiment,fluorescence quenching experiment,on/off experiment,deuterium labeling experiment and so on.The results indicated that the free radical process,visible light-mediated energy transfer process and intramolecular hydrogen transfer process maybe involved in this transformation.Combined with previous reports,the possible mechanism was given.The reaction conditions are mild and the substrate has good broad-spectrum properties.Phenanthrene-9,9（10H）dinitrile and its derivatives can be efficiently synthesized.（2）Under metal-free conditions,a simple and effective method for the synthesis of fluorenone by dehydrogenation coupling reaction of 2-phenylbenzaldehyde was developed.Firstly,the optimal reaction conditions were obtained by the reaction conditions optimization.Then,17 compounds were obtained in 58-83%yield under the optimum reaction conditions.and their structures were determined by ¹H NMR and¹³C NMR.However,only some simple group substituted substrates have been synthesized.In addition,the reaction mechanism was explored by free radical quenching experiment.The results indicated that the free radical process maybe involved in this transformation.The reaction conditions are mild,and the substrate has good broad-spectrum properties.Fluorenone and its derivatives can be efficiently synthesized.