Yang Xiaobo, associate professor of Shenyang Normal University Research Group: covalent organic framework materials catalyse visible light to promote free radical addition and cyclization of 2-isocyanobenzene

COFS is a kind of organic porous materials with crystalline and periodic structure formed by covalent bond Two dimensional covalent organic framework materials have extended π conjugation system, which promotes photogenerated electrons- Compared with inorganic semiconductor photosensitizers, the optical band gap, redox potential and absorption range of holes can be adjusted by framework adjustment and design Therefore, as photosensitizers, holes have the potential to achieve visible light to promote organic reactions, but they are currently applicable The type of organic reaction is limited to the cross dehydrogenation coupling reaction (CDC reaction) driven by visible light and the simple oxidation-reduction reaction Recently, the research group of Yang Xiaobo, associate professor of Shenyang Normal University, took the 2D covalent organic framework material (2d-cof-1) with imine as the linking group as photosensitizer, realized the free radical addition and cyclization reaction of 2-isocyanobiphenyl promoted by visible light (Figure 1), and synthesized a variety of 6-substituted phenanthridine derivatives by using this reaction This method is simple, efficient and has good substrate applicability, which effectively widens the application scope of two-dimensional covalent organic framework materials in photoorganic transformation In addition, the researchers realized the effective recovery and recycling of photosensitizers through the cycle test and flow chemistry research of photosensitizers, and showed the possibility of its amplification experiment and the practicability of the reaction Relevant research results were published in green chem (greenchem 2019, DOI: 10.1039 / c9gc00022d) Fig 1 introduction of Yang Xiaobo, associate professor, master's supervisor, and associate professor of free radical addition and cyclization of 2-isocyanophenyls by catalytic visible light of covalent organic framework materials He graduated from Beijing University of Chemical Technology in July 2007, Tsinghua University in July 2013, and visited McGill University in Canada from 2016 to 2017 as a visiting scholar (co Tutor: Professor Li Chaojun) Since September 2013, I have worked in the Department of chemistry, School of chemistry and chemical engineering, Shenyang Normal University In 2014, it was selected into the excellent talents support plan of Liaoning colleges and universities, in 2018, it was selected into the innovation talents support plan of Liaoning colleges and universities, and Shenyang young and middle-aged science and technology innovation talents support plan In 2018, it was rated as the 13th excellent science and technology worker of Shenyang His research interests are Photopromoted organic reactions and transition metal catalyzed C-H bond activation reactions He has published more than 20 high-level academic papers in authoritative academic journals in the field of chemistry, such as J am Chem SOC., chem, greenchem., org Lett., chem EUR J., adv synth Catalyst Apply for 1 domestic patent and 1 authorization It was supported by 8 projects including the National Natural Science Foundation and Liaoning Natural Science Foundation Introduction to the research group of Associate Professor Yang Xiaobo there are 1 associate professor, 1 lecturer, 4 postgraduates and several undergraduates in the research group Relying on the "energy and environmental catalysis engineering technology research center", a major science and technology platform in Liaoning Province, the laboratory of the research group has fully possessed the equipment and conditions for the synthesis and characterization of covalent organic framework materials and the development of light promoted organic transformation and transition metal catalysis At present, the main research directions of the research group are light promoted organic reactions (chem EUR J 2016, 22, 5252; J am Chem SOC 2017, 139, 8621; adv syn Catalyst 2018, 360, 267; green chem 2019, DOI: 10.1039/c9gc00022d.) and transition metal catalyzed C-H bond activation (org Lett 2018, 20, 6573; org Chem Front 2017, 4250; RSC Adv 2017 , 7, 20548; RSC Adv 2016 , 6,57371 ）。 Cutting edge research achievements: covalent organic framework materials catalyse visible light to promote free radical addition of 2-isocyanobiphenyl and cyclization of covalent organic frameworks, COFS), as a new type of porous crystalline material with periodicity, has the characteristics of high stability and large specific surface area, so it has a wide application prospect in adsorption, catalysis, photoelectric materials, energy and other fields In 2D COFS, the periodic π conjugation system can promote the carrier transport in the stacking direction, which makes 2D COFS have the potential to realize photoorganic conversion However, the scope of photoorganic reaction for 2D COFS is limited to the visible light driven CDC reaction and simple oxidation-reduction reaction Phenanthridine derivatives are widely used in natural products, drugs and materials, so their synthesis methods are also concerned In the past few decades, many excellent methods have emerged to synthesize these compounds Among them, the free radical addition and cyclization strategy based on visible light induced 2-isocyanobenzene has become the most attractive strategy for the synthesis of such compounds (scheme 1a) due to its high efficiency, green and reasonable use of light energy However, in the previous methods, the photosensitizers used are homogeneous photosensitizers Although they have high efficiency, they are not easy to separate and recycle, and metal complexes are expensive, which greatly limits their practical application In order to solve the above problems and expand the application of 2D COFS in photoorganic conversion, Yang Xiaobo's research group took 2D covalent organic framework material (2d-cof-1) with imine as the linking group as the recyclable and reusable heterogeneous photosensitizer, realized the heterogeneous visible light to promote the free radical addition cyclization of 2-isocyanophenyls, and synthesized a variety of different types of 6-substituted phenanthridine derivatives (scheme 1b) (source: Green chem.), 2d-cof-1, a two-dimensional covalent organic framework material, was prepared by 5-dimethoxy-p-benzoylhydrazide and m-trimethylbenzaldehyde Its structure, properties, morphology and photoelectric activity were measured and characterized Then, it was compared with traditional homogeneous photosensitizers in two key photochemical activity parameters, i.e absorption wavelength and redox potential (Fig 1) The results show that the synthesized 2d-cof-1, as a heterogeneous photosensitizer, has the similar photochemical activity with the homogeneous photosensitizer, and has the potential to achieve photoorganic transformation (source: Green chem.) then, in order to verify the photosensitive activity and applicability of covalent organic framework material 2d-cof-1 in the visible light promoted free radical addition and cyclization of 2-isocyanobenzene, the author first took phenylhydrazine as the precursor of phenyl free radical, 2-isocyanobenzene as the receptor of free radical, and 2d-cof-1 as the photosensitizer Under the appropriate reaction conditions, blue LED Try under the light The experimental results show that it can achieve the free radical addition and cyclization of 2-isocyanobiphenyl, and obtain 6-phenylsubstituted phenanthridine 3AA in 77% yield Subsequently, the substrate applicability of the reaction was further investigated The results showed that the selected 2-isocyanophenyls could be transformed well no matter where the substituents were and what type of substituents they were In addition, 6-tert-butyl-substituted phenanthridine could be obtained by using tert butyl hydrazine 2C as the precursor of alkyl radical in a very high yield Compared with the previously reported reaction using homogeneous photosensitizers, the yield was almost the same (Table 1) (source: Green chem.) later, in order to expand the application of heterogeneous photosensitizer 2d-cof-1 to this type of reaction, the author also selected sodium trifluoromethane sulfite, diphenylphosphine and diphenyldisulfide as free radical precursors, and tried to produce corresponding free radicals through the oxygen reduction reaction with photosensitizer under visible light irradiation- The free radical addition and cyclization (Table 2, scheme 2) were carried out for isocyanobenzene Through a series of experiments, it is found that the heterogeneous photosensitizer 2d-cof-1 can well catalyze the reaction and synthesize the corresponding 6-substituted phenanthridine derivatives, and the substrate of the reaction has good applicability, which is not affected by the electronic effect and space effect Heterogeneous photosensitizers did not significantly affect the efficiency of the reaction, and even the yield of some target products was higher than previously reported In addition, ethyl acetate, the solvent used in the reaction, is less toxic, greener and easier to operate than the reported solvent, which shows the practicability and operability of the method in practical operation (source: Green chem.) (source: Green chem.) finally, in order to show the advantages of heterogeneous photosensitizer 2d-cof-1 in recycling in this experiment, the author carried out a cyclic experiment for the reaction in scheme 3a The results showed that the recovery rate of the target product was almost unchanged, all of which were more than 90% when the photosensitizer 2d-cof-1 was reused for 6 times In addition, the reaction of 2-isocyano-4 '- methoxy-1,1' - biphenyl (1a) and diphenyl disulfide ether 6 was amplified by using a self-made flow reactor The experimental results show that: the preparation of gram scale can also obtain good yield, and the catalyst is easy to recover, which further shows the practicability and operability of the method (source: Green chem.) to sum up, Yang Xiaobo's research group reported a new synthesis method of various 6-substituted phenanthridine derivatives by using 2d-cof-1 as heterogeneous photosensitizer, which can promote free radical addition and cyclization by visible light The reaction conditions of this method are mild, simple and efficient, with good functional group tolerance The heterogeneous photosensitizers used in the reaction are easy to separate and recover In addition, the high practicability and operability of the method are further demonstrated by the circulation experiment and flow chemistry experiment This achievement was recently published in green chem (DOI: 10.1039 / c9gc00022d) The first author of this paper is Liu Shuyang, a master student of the school of chemistry and chemical engineering of Shenyang Normal University, Yang Xiaobo, an associate professor of Shenyang Normal University, Xu Hao, an associate professor of Henan University, and Yu Jipan, an assistant researcher of the Institute of high energy physics of the Chinese Academy of Sciences The related work has been supported by the National Natural Science Foundation of China, Liaoning Natural Science Foundation, Liaoning university innovation talents support plan, Liaoning Provincial Department of education basic scientific research project, Shenyang young and middle-aged science and technology innovation talents support plan Nowadays, people and scientific research have been paid more and more attention in the economic life China has ushered in the "node of science and technology explosion" Behind the progress of science and technology is the work of countless scientists In the field of chemistry, in the context of the pursuit of innovation driven, international cooperation has been strengthened, the influence of Returned Scholars in the field of R & D has become increasingly prominent, and many excellent research groups have emerged in China For this reason, CBG information adopts the 1 + X reporting mechanism CBG information, chembeangoapp, chembeango official microblog, CBG wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the domestic representative research group, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit.