Project team of Professor Liang Fushun of Liaoning University: Construction of f-n-containing heterocycles initiated by electron donor receptor complex and promoted by visible light

The nitrogen-containing heterocyclic compounds are widely found in nature, such as alkaloids, morphine, quinine, camptothecin and blood equality Statistics show that about 30% of heterocyclic compounds are nitrogen heterocycles On the other hand, because the atomic radius of fluorine atom is small (1.47 Å) and the electronegativity is the largest (χ P = 4.0), the introduction of fluorine unit into the molecule will greatly improve the lipophilicity, membrane permeability, metabolic stability, pharmacology and biological activity of the molecule In terms of materials, the introduction of fluorine-containing groups can effectively regulate the energy level, excited state properties and stacking properties of molecules Therefore, the synthesis and properties of fluorine-containing nitrogen heterocycles have been widely concerned Recently, the research group of Professor Liang Fushun of Liaoning University has focused on the organic reactions induced by electron donor receptor complex and promoted by visible light (Figure 1) In 2017, researchers realized the construction of fluoropyrimidine through the "one pot multi-component" [2 + 1 + 3] cyclization reaction (org Lett 2017, 19, 2358) The results show that the electron donor acceptor complex can be effectively formed between enol anion and polyfluoroalkane halide On the basis of this study, the researchers synthesized aza tricyclic compounds with aggregation induced luminescence (AIE) properties by adding the organic base DBU with C and N amphiphilic properties (org BIOMOL Chem 2018, 16, 8950) Recently, researchers have realized the [5 + 1] cyclization between visible light promoted biguanide substrate and polyfluoroalkyl iodine, and synthesized 6-polyfluoroalkyl-triazine (org Lett 2019, DOI: 10.1021/acs.orglett 9b00655) Figure 1 The construction of fluorine-containing heterocycles induced by electron donor receptor complex Dean, Institute of organic luminescent materials, Liaoning University In 2002, he obtained his doctorate from Changchun Institute of Applied Chemistry, Chinese Academy of Sciences; in 2003-2005, he carried out postdoctoral research in Waseda University (supported by JSPS scholarship); in 2007-2008, he carried out visiting research in National Research Institute of Canada (supported by NSERC scholarship) In 2011, it was selected into the "new century talent support plan" of the Ministry of education From May 2005 to August 2016, he worked in the school of chemistry of Northeast Normal University In August 2016, he transferred to Liaoning University Professor Liang Fushun has published more than 70 papers in famous academic journals at home and abroad, and has been cited more than 1600 times It has undertaken 3 general projects of NSFC The representative papers are: J am Chem SOC 1; angel Chem Int ed 1; chem Commun 7; org Lett 14; chem Mater 1; macrolecules 1; app Physics Lett 1 At present, there are 3 doctoral students and 7 master students in the research group Research interests focus on new reactions, the development of new materials and the establishment of new concepts It includes: new organic reactions catalyzed by visible light and organic photoelectric materials We have obtained anion relay series (j.am Chem SOC., 2011, 133, 1781), extended life of organic room temperature phosphorescent materials by D-P π bond (angel Chem Int ed., 2019, DOI: 10.1002/anie.201901546), and n-haloimide activated by halogen bond as aminating agent (org Lett., 2012, 14, 4202) and electroluminescence based on excited state intramolecular transfer (ESIPT) (appl Phys Lett., 2002, 81, 4) Frontier research achievements: the research on the construction of triazine derivatives initiated by electron donor receptor complex and promoted by visible light started in the mid-1950s It is a structural unit of many natural products with biological and pharmaceutical activities, widely used in the fields of herbicidal, bactericidal, antiviral and other medicine and pesticide Due to the inherent characteristics of triazine, it can also be used in photoelectric materials, flame retardant materials, UV blocking materials, energetic materials and porous materials (Fig 2) Therefore, its synthesis method has been widely concerned Figure 2 The structure of representative functionalized triazine (source: org Lett.) biguanide can be used as the precursor of synthesis of triazine due to its own structural characteristics Most of the previously reported synthesis of triazine based on biguanide substrate is based on thermally initiated reactions, such as acylation / cyclization of biguanide with a suitable ester (Fig 3a), and transition metal catalyzed reactions of biguanide with a suitable alcohol or dihaloalkene (Fig 3b, c) Recently, on the basis of previous work, Professor Liang Fushun's research group has realized [5 + 1] cyclization between visible light promoted biguanide substrate and polyfluoroalkyl iodine, and synthesized 6-polyfluoroalkyl-triazine (Fig 3D) Subsequently, the author made an in-depth study of this reaction Fig 3 Representative synthesis method of triazine (source: org Lett.) firstly, the author optimized the reaction conditions with metformin hydrochloride and perfluorodiiodobutane as model substrates After obtaining the best reaction conditions, the author further expanded the range of substrates Different biguanidine substrates (Table 1) and polyfluoroalkyl iodine (Table 2) are well compatible More importantly, the reaction can be used for the introduction of trifluoromethyl, a common drug molecule (product 4a) Table 1 substrate range of biguanide (source: org Lett.) table 2 substrate range of polyfluoroalkane halide (source: org Lett.) in order to further demonstrate the practicability of this method, the author synthesized molecule 5 and ditriazine product 6 with herbicidal activity at seedling stage (Fig 4) Fig 4 Method development (source: org Lett.) in order to explore the reaction process, the author conducted a series of control experiments, such as UV-Vis absorption spectrum (Fig 5a, b) and quantum yield test (Fig 5C, d) The results show that the formation of electron donor acceptor complex and the single electron transfer are the key to the reaction Fig 5 Control experiment (source: org Lett.) based on the above-mentioned control experiment, the author proposed the possible reaction mechanism (Fig 6): first, biguanide anion I forms electron donor receptor complex II with perfluorodiobutane 1a, which gets triple excited state II * under the excitation of visible light; then, II * forms biguanide free radical through single electron transfer Finally, the target product was obtained by eliminating HF, 6 π cyclization and aromatization Figure 6 Possible reaction mechanism (source: org Lett.) Summary: This study found that biguanide anion can form electron donor acceptor complex with polyfluoroalkyl iodine In the absence of photosensitizer and transition metal catalyst, 6-polyfluoroalkyl-triazine was successfully synthesized by the visible light promoted [5 + 1] cyclization strategy Further research shows that visible light and oxygen in the air play the roles of promoting the production of triplet excited states and "electron shuttle", respectively, so that the series reaction can proceed smoothly Related achievements were published in org Lett (DOI: 10.1021 / ACS Orglett 9b00655) Wang Rui, a doctoral candidate of Northeast Normal University, was the first author of the paper The corresponding authors are Ren Baoyi, associate professor of Shenyang University of chemical technology and Liang Fushun, Professor of Liaoning University 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.