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    Home > Cao song, Professor, East China University of science and technology research group: palladium or iron catalyzed defluorination and boration of aryl fluoride promoted by LiHMDS

    Cao song, Professor, East China University of science and technology research group: palladium or iron catalyzed defluorination and boration of aryl fluoride promoted by LiHMDS

    • Last Update: 2018-09-29
    • Source: Internet
    • Author: User
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    It is a hot research field in fluorine chemistry, organic synthesis and organometallic chemistry to break, activate and functionalize the carbon fluorine bond of different fluorine-containing compounds (fluorine-containing aromatics, fluorine-containing olefins, fluorine-containing alkanes) In the past two decades, the results show that the carbon fluorine bond is difficult to break under the influence of different adjacent groups or under different reaction conditions, sometimes it is easy to be attacked, showing the diversity and complexity of the reaction It is the specificity and uncertainty of fluorocarbon bond that makes the fracture of fluorocarbon bond become a challenging topic in organic synthesis The researchers hope to find more new reactions by using the cleavage and activation of carbon fluorine bond to synthesize organic small molecules with various structures Recently, Professor Cao song's research group of East China University of science and technology reported the scheme 1 of palladium or iron catalyzed defluorination and boration of aryl fluoride promoted by LiHMDS, and relevant results were published in org Lett (DOI: 10.1021 / ACS Orglett 8b02228) Prof Cao song's research team has been committed to the fracture and activation of fluorine-containing aromatic hydrocarbons and fluorine-containing alkenes, and has developed many new reactions and methods based on the fracture of fluorine-containing carbon bonds (org Lett., 2017, 19, 3283; org Lett., 2016, 18, 4284; chem EUR J, 2016, 22, 9902; org Lett., 2016, 18, 2918; Adv Synth Catal , 2016 , 358 , 183; Org Lett , 2015 , 17 , 5069; Org Lett , 2015 , 17 , 2708; Org Lett , 2013 , 15 , 3114; Chem Commun , 2012 , 48 , 8553 )。
    Introduction to Professor Cao song, Professor Cao song, doctoral supervisor He has obtained bachelor's degree, master's degree and doctor's degree in Chemistry Department of East China Normal University, School of chemistry and chemical engineering of Nanjing University and School of chemistry and pharmacy of East China University of science and technology Since 2000, he has been engaged in scientific research and teaching in the school of chemistry and pharmacy, East China University of science and technology From April 2006 to April 2007, as a visiting scholar, I went to the Department of chemistry of Northwestern University to design and synthesize Parkinson's drugs July 2013 – October 2013: as a senior visiting scholar, he went to the Department of chemistry, University of Southampton, UK to design and synthesize drugs As the project leader, he has undertaken the scientific and technological innovation and research project of Shanghai Science and Technology Commission, and three general projects of NSFC: "synthesis of difluoromethyl (CF 2)" New strategy of small molecules with structural diversity, activation of carbon and fluorine bonds of PFA catalyzed by transition metals: hydrocarbon and functionalization, and carbon carbon coupling reaction based on activation of carbon and fluorine bonds and hydrocarbon bonds, one of the 12th Five Year Plan for science and technology support, one of the 863 projects and one of the 973 subprojects as the vice leader of the research group He has published more than 70 papers in international core academic journals as the main author, authorized five national invention patents, and published ten Chinese invention patents and one international patent At present, he guides more than doctoral and postgraduate students Leading scientific research achievements: fluorination and boration of aryl fluoride carbon bond catalyzed by palladium or iron under the promotion of LiHMDS Coupling reaction can show strong reaction performance, so this kind of compounds are widely used in drugs and materials In recent years, the synthesis of Organic Borates has become the frontier research field of organic synthesis Generally speaking, the boration of halogenated aromatic hydrocarbons (iodo, brominated, chlorinated aromatic hydrocarbons) and bispinacol borates (B 2pin 2) catalyzed by transition metals is an effective method to synthesize aryl borates, while fluorinated aromatic hydrocarbons are not suitable substrates for boration In recent years, it has been reported that nickel, copper and rhodium catalysts are used for the defluorination and boration of aryl fluorine and polyfluorobenzene Scheme 1 LiHMDS promoted the defluorination and boration of aryl fluoride catalyzed by palladium or iron Firstly, the author screened the reaction conditions with p-phenylfluorobenzene (1a) and B 2pin 2 as substrates (Table 1) The results showed that with toluene as solvent, 2 mol% PD 2 DBA 3 as catalyst, 2.0 equivalent LiHMDS as base, the reaction temperature was 80 ℃, 1a and 1.5 equivalent B 2 pin 2 were reacted under the protection of argon for 12 hours, and the yield was the highest (entry 20) Table 1 Screening of reaction conditions (source: org Lett., 2018, 20, 5564-5568) After selecting the optimal reaction conditions, the author investigated the universality of aryl fluoride substrates (scheme 2) The products of boronization can be obtained in good yields from aryl fluorine containing electron donor groups (such as methoxy, amino group) and aryl fluorine (such as carbonyl group) with medium electron acceptor groups The reaction has good compatibility with amino group, carbonyl group, trifluoromethyl group, alkoxy group and boron group Primary amines, secondary amines and carbonyls can also be compatible with the reaction conditions, which provides the possibility for further functional group derivatization This advantage has not been reported in other aryl fluorine defluorination and boration reactions Scheme 2 Investigation on the substrate range of palladium catalyzed defluorination and boronization of aryl fluoride (source: org Lett., 2018, 20, 5564-5568) Then, in order to verify the practicability of the reaction, the author expanded the defluorination and boronization of 1-Naphthalene fluoride (1J) under the optimal conditions It is gratifying that 1 mol% PD 2 DBA 3 can make the reaction go on smoothly and get the target compound (scheme 3) in medium yield Scheme 3 Gram scale reaction (source: org Lett., 2018, 20, 5564-5568) iron catalyst has the advantages of low cost, easy access, low toxicity and environmental protection In order to further expand the defluorination and boration reaction of carbon fluorine bond catalyzed by transition metal, the author preliminarily studied the defluorination and boration reaction of aryl fluorine catalyzed by iron After the investigation of reaction factors such as catalyst, solvent, alkali, additive, etc., it was found that the defluorination and boration reaction of arene fluorine can proceed smoothly in FeCl2 / LiHMDS / toluene / HMPA system Unfortunately, the substrate expansibility and functional group compatibility of this method still need to be improved (scheme 4) Scheme 4 Investigation on the substrate range of iron catalyzed defluorination and boronization of aryl fluoride (source: org Lett., 2018, 20, 5564-5568) Finally, the author proposed the possible reaction mechanism of palladium catalyzed defluorination and boronization of aryl fluoride The strong base LiHMDS plays a key role in the reaction It can activate the B-B bond of borates This reaction has experienced the oxidation addition of zero valent palladium to fluorocarbon bond, the transition metallization of complex larpd (II) f with Lewis adduct of diborane, and the reduction elimination of palladium complex (scheme 5) Scheme 5 Possible reaction mechanism (source: org Lett., 2018, 20, 5564-5568) In addition, in 2017, Professor Cao song's research team also reported the reaction of bifluoroethylene with B 2pin 2 Catalyzed by copper, and obtained a series of Z-type monofluoroalkenylborates (scheme 6) In order to verify the applicability of the novel Z-type monofluoroalkenyl borate, the author derived various stereoisomeric monofluoroalkenes (scheme 7) by using the excellent reaction performance of the borate group The work was published in org Lett (DOI: 10.1021/acs.orglett.7b01430) Scheme 6 Scheme 7 Derivatization of monofluoroalkenylborate (z) - 3A (source: org Lett., 2017, 19, 3283-3286) palladium or iron catalyzed boration of aryl fluorine was completed by Zhao Xianghu, Ph.D., and copper catalyzed boration of gemal difluoroethylene was completed by Zhang Juan, Ph.D (Zhang Juan is now a postdoctoral student of Chongqing 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.
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