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    Home > Xie Jin and Zhu Chengjian of Nanjing University made important breakthrough in visible light catalysis

    Xie Jin and Zhu Chengjian of Nanjing University made important breakthrough in visible light catalysis

    • Last Update: 2018-08-30
    • Source: Internet
    • Author: User
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    Author: Wang Dongping recently, Xie Jin group and Zhu Chengjian group of the research team of molecular and material synthesis, School of chemistry and chemical engineering, Nanjing University made an important breakthrough in the visible light catalyzed deoxidization mechanism of aromatic carboxylic acids, and realized the direct deoxidation carbon coupling of aromatic carboxylic acids under mild conditions for the first time This achievement was published online on nature communications (DOI: 10.1038 / s41467-018-06019-1) on August 29, 2018 under the title of "a general deoxygenation approach for synthesis of ketones from aromatic acids and alkenes" The first author of the paper is Zhang Muliang, a 2016 level doctoral student Associate Professor Xie Jin and Professor Zhu Chengjian are the corresponding authors of the paper Aromatic carboxylic acid is a kind of cheap, easy to get and rich chemical raw materials Through the activation of carboxylic acid functional group, we can quickly enrich the database of organic small molecular compounds After nearly ten years of development, palladium, silver and copper catalyzed deacidification and coupling strategies have made aromatic carboxylic acids a cheap aromatic source, while carboxylic acids as acyl sources are rarely reported It is found that the C-C and C-O bonds of aromatic carboxylic acids have similar bond dissociation energy (BDE) (103 vs 102 kcal / mol), which challenges the accurate C-O bond functionalization (scheme 1a) No matter in the classical organic textbooks or in the frontier field of organic synthesis, chemists need to pre activate the aromatic carboxylic acid, transform it into corresponding intermediates such as acyl chloride, ester, anhydride and amide, and then use the corresponding intermediates in various kinds of metal catalyzed coupling reactions to synthesize aromatic ketone compounds (scheme 1B) The application of scheme 1 aromatic carboxylic acid in organic synthesis (source: Nat Commin.) was inspired by the classical Wittig reaction, and the team developed a new mechanism of direct deoxidization and activation of aromatic carboxylic acid catalyzed by triphenylphosphine cation free radical in visible light It breaks through the limitation of the substrate dependent redox potential in the photocatalytic system and provides a new method (scheme 1c) for the rapid and efficient construction of aromatic ketones Firstly, the applicability of the carboxylic acid substrate was investigated, and it was found that all kinds of O -, M - and p-substituted aromatic carboxylic acids were excellent substrates, while heterocyclic aromatic acids were well compatible and could obtain medium yield A series of more sensitive functional groups, such as amino group, hydroxyl group, aldehyde group, terminal alkene and terminal alkyne, do not affect the normal process of the reaction (scheme 2) Compared with other transition metal catalytic systems, the system is also compatible with aryl halides which are prone to electrophilic addition and easy to be derived and transformed However, fatty acids, unsaturated enoic acids and alkynes are still difficult substrates Scheme 2 aromatic carboxylic acid substrate development (source: Nat Commin.) the author then tried a variety of pyridine alkenes, and found that no matter single, double or non terminal pyridine alkenes can participate in the reaction well In addition, styrene is also a good acyl free radical receptor, which can be used to enrich the structure diversity of aromatic ketone database It is worth mentioning that the coupling of aromatic carboxylic acids with unsaturated alkenes provides a promising method for the preparation of 1,4-dicarbonyl compounds (scheme 3) In a word, the method has mild reaction conditions, excellent functional group tolerance and a wide range of substrate applications, which provides a new convenient method for the construction of complex aromatic ketone compounds which are difficult to be prepared by traditional methods In addition, the catalytic system has good biocompatibility with natural amino acids, proteins, drug molecules and other bioactive molecules, and its advantages are further reflected A series of complex aromatic carboxylic acids and alkenes can be well compatible Therefore, this strategy can be directly applied to the synthesis and post modification of complex natural product molecules, providing a new method to directly construct complex aromatic ketone compounds from aromatic carboxylic acids (scheme 4) Zolpidem is a new type of non benzene sedative and hypnotic drug with fast action, good effect and light side effect It was first developed by Sanofi Aventis in France Developed by the company, it has been listed in more than ten countries, such as France, the United States and the United Kingdom It is widely used as sedative and hypnotic drugs around the world and has the trend of gradually replacing benzene drugs Zolpidem ranked 28th among the top 200 drug molecules in 2016 The patent protection method uses bromo p-methyl acetophenone as the raw material, which needs to undergo 6 steps of reaction, and the total yield is 19% Using the direct deoxidizing carbon coupling strategy of aromatic carboxylic acid invented by the author, the synthesis of zolpidem (scheme 5) can be realized in a total yield of 50% through three steps starting from cheap large chemical raw material p-methylbenzoic acid The synthesis of scheme 5 zolpidem (source: Nat Commun.) at the same time, the synthesis technology can also be applied to the synthesis of challenging macrocyclic ketones, and 18-20 ring aromatic CYCLOKETONE products (scheme 6) can be obtained in medium yield Synthesis of scheme 6 macrocyclic ketone (source: Nat Commun.) Conclusion: Xiejin and Zhu Chengjian research team have successfully solved the problem of relying heavily on the redox potential of the substrate itself in the photocatalytic system by developing the synergistic effect of visible light and heteroatom radicals, which makes the developed synthesis method have better universality and generality The team has published several research papers in this field in the past year (NAT Commun 2018, DOI:10.1038/s41467-018-06019-1; Angew Chem.Int Ed 2018 , 57 , 3990; Angew Chem Int Ed 2018 , 57 , 10357 )。 Using the synergistic effect of visible light catalysis and phosphine radicals, the team realized the direct C-O bond activation of aromatic carboxylic acids under mild conditions for the first time, further enriched and developed the new deoxygenation chemistry of carboxylic acids, and successfully constructed a series of aromatic ketones with diverse and complex structures The above research work was supported by the youth thousand talents program of the Central Organization Department, the talent support program of Nanjing University, the National Natural Science Foundation, and the basic scientific research business fees of the Central University Thanks for the great support provided by the school of chemistry and chemical engineering and the State Key Laboratory of coordination chemistry in the early stage of the construction of Xiejin research group At the same time, I would also like to thank Dr Zhang Muliang for his support from the innovative and creative research program of Nanjing University The team has long invited young talents from home and abroad to join in to explore the charm of synthesis, appreciate the meaning of scientific research and appreciate the beauty of chemistry Review of previous reports: Xie Jin and Zhu Chengjian research team of Nanjing University: synergistic catalysis of TERT ether polar inversion trifluoromethylthiolation
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