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    Home > Zhang ChengPan research group of Wuhan University of Technology: Organic visible light catalysis [Me4N] [secf3] for oxidative decarboxylation of fatty acids

    Zhang ChengPan research group of Wuhan University of Technology: Organic visible light catalysis [Me4N] [secf3] for oxidative decarboxylation of fatty acids

    • Last Update: 2019-12-28
    • Source: Internet
    • Author: User
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    In recent years, more and more attention has been paid to the introduction of secf3 because of its unique stereoelectronic effect and lipophilicity Although the compounds containing Trifluoromethoxy and trifluoromethylthiol have been widely used in the fields of medicine, pesticide and veterinary medicine, the drugs containing trifluoromethylselenyl have not been reported This may be due to the lack of the number of compounds containing trifluoromethylselenyl, the lack of relevant biological activity research data, and the limited synthesis methods There have been some reports on the synthesis of trifluoromethylselenide by [me 4N] [SECF 3], but almost all of them are reactions of [me 4N] [SECF 3] to electrophilic substrate, but there are few reports on the reactions of [me 4N] [SECF 3] to electrophilic substrate In addition, free trifluoromethylselenyl anions are easily over oxidized by common oxidants to high selenium species, so it is a great challenge to apply it to oxidative coupling reactions Recently, Zhang ChengPan group of Wuhan University of science and technology realized the decarboxylation and trifluoromethane selenidation of [me 4N] [SECF 3] to fatty acids without the participation of transition metals by using the visible light catalytic oxidation strategy The related results were published on org Lett (DOI: 10.1021 / ACS Orglett 9b03941) Prof Zhang ChengPan's brief introduction the research group has been committed to the synthesis and reaction of functional fluoroorganics, and has made a lot of progress in trifluoroethylation, trifluoromethylselenidation and sulfonium salt aromatization So far, the research group has published more than 60 papers in internationally renowned journals and has been cited for more than 1900 times At present, the research group has 2 doctoral students and 8 master students Prof Zhang ChengPan, professor and doctoral supervisor of School of chemistry, chemical engineering and Life Sciences, Wuhan University of technology In 2011, he graduated from Shanghai Institute of organic chemistry, Chinese Academy of Sciences From 2011 to 2012, he worked in the research group of Professor David A Vicic of the University of Hawaii, and from 2012 to 2014, he worked in John a of Texas A & M University Professor gladysz's research group is engaged in postdoctoral research In 2014, he joined Wuhan University of science and technology, and was selected into Hubei Province's "Chutian scholar" plan, Wuhan University of science and technology's "15551 talent project" young top talents, Wuhan Youth Science and technology morning light plan, and the sixth batch of "hundred talents plan" in Hubei Province Leading scientific research achievements: Organic visible light catalyzed oxidative decarboxylation of fatty acids by [me 4 N] [SECF 3] Up to now, the methods of introducing SECF 3 directly into the organic framework can be roughly divided into the following three kinds: nucleophilic, electrophilic and free radical trifluoromethylselenidation The trifluoromethylselenides involved mainly include Hg (SECF 3) 2, Cusecf 3, [(bpy) cusecf 3] 2, [me 4 N] [SECF 3], Ag SECF 3, clsecf 3 and tssecf 3 Among these reagents, [Me4N] [secf3] has become one of the most important trifluoromethylselenidation reagents because of its good thermal stability, convenient use, low price and easy preparation Recently, Zhang ChengPan's research group has successively developed nickel catalyzed trifluoromethane selenidation of aryl iodides, bromines and chlorides using [me 4N] [SECF 3] as a trifluoromethane selenide source (org Lett 2017, 19, 3919-3922), the nucleophilic trifluoromethylselenidation of alkynyl polyiodides, organic halogenated compounds, diaryl iodides, aryldiazonium salts and α - diazo carbonyl compounds without transition metals and additives (org BIOMOL Chem 2016, 14, 11502-11509, ACS sustainable chem Eng 2018, 6, 1327-1335), as well as the C-H bond oxidation of electron rich aromatic hydrocarbons (org Chem Front 2019, 6, 2732-2737) The latter is the first coupling reaction between the nucleophilic trifluoromethylselenyl ammonium salt and the nucleophilic substrate Fig 1 based on the above research work, the research group proposes to use a large number of cheap and stable fatty acids in nature as the alkylation source, and use green and efficient photocatalytic strategy to study the oxidative decarboxylation of fatty acids With [me 4N] [SECF 3] as the reagent, pH I (OAC) 2 or NFSI as the oxidant, blue LED as the light source, and [MES ACR pH] [BF 4] or [MES ACR me] [BF 4] as the photocatalyst, the decarboxylation of first-order carboxylic acids with different substituents was carried out very gently without the participation of transition metals 2-arylacetic acid derivatives with methyl, methoxy, methanesulfonyl, phenyl, phenoxy, phenoxybenzyl, halogen, nitro and other functional groups on the aromatic ring can obtain the corresponding trifluoromethylbenzylselenide in medium to good yields It is worth mentioning that 2-naphthyloxyacetic acid and 2 - (8-chloro-1-naphthylthio) acetic acid can also obtain the target products in 65% and 31% yields respectively under the standard conditions By prolonging the reaction time and using purple LED as the light source, the corresponding trifluoromethylselenide products can be obtained in medium yield Fig 2 decarboxytrifluoromethane selenidation of fatty acids by [me 4N] [SECF 3] under the action of oxidant and visible light (source: org Lett.) in order to further verify the usefulness of this method, the author also applies this reverse method to the later modification of a series of drugs and natural products It is gratifying to note that the target product can be obtained in 42-88% yield from isolac acid, sodium bromfenate, indomethacin, palmitic acid and oleic acid; for typical secondary carboxylic acid drug molecules, such as ibuprofen, naproxen, pramiphene and Caroline, the yield of trifluoromethylselenide is up to 82% Keto carbonyl, free amino group, amide, olefin and heterocycle can be tolerated in the reaction 1- adamantanic acid can also be used to obtain the target product with 55% fluorine spectrum yield (36% separation yield) The results show that the reaction is suitable for decarboxylation and trifluoromethane selenidation of secondary and tertiary carboxylic acids Fig 3 decarboxytrifluoromethylselenidation of complex fatty acids by [Me4N] [secf3] (source: org Lett.) in addition, the author also investigated the possible reaction mechanism First of all, the free radical inhibitors such as BHT, 1,1-stilbene, diallyl PTSA and tempo were added to the standard reaction, and trifluoromethylselenidation was inhibited or completely blocked, indicating that the reaction may have experienced a free radical process At the same time, EPR experiment also confirmed the formation of alkyl and trifluoromethylselenium radical Through the fluorine spectrum tracking of the reaction solution, the author found that there was the formation of CF 3 sesecf 3 intermediate in the reaction, and with the progress of the reaction, the in-situ formation of CF 3 sesecf 3 was gradually consumed, while the yield of the target product increased Therefore, CF 3 sesecf 3 may be the key intermediate of the reaction In addition, the experiment of switching on and off light shows that the reaction is light driven, that is, the reaction stops when there is no light In conclusion, the author speculates that the reaction may go through the following processes: first, the catalyst [MES ACR pH] + generates [MES ACR pH *] + under visible light irradiation, and generates [MES ACR pH] • and acyloxy radicals (I) through single electron transfer with carboxylic acid anion I remove CO2 to form alkyl radical (II) At the same time, [me 4N] [SECF 3] can generate trifluoromethylselenyl radical under the action of oxidant, and self couple to CF 3 sesecf 3 Trifluoromethylseleno radical and CF 3secf3 can react with alkyl radical (II) to prepare trifluoromethylselenide products Finally, [MES ACR pH] • regenerates [MES ACR pH] + under the action of oxidant, and then enters the next catalytic cycle Among them, the reduction products of oxidants such as (phso2) 2n ‒, f – and – OAC anions can be used as bases to deprotinate carboxylic acids to form carboxylic acid radicals, which can further promote the decarboxylation reaction Fig 4 possible reaction mechanism (source: org Lett.) to sum up, the author realized the oxidative decarboxylation of primary, secondary and tertiary fatty acids by nucleophilic [Me4N] [secf3] through the strategy of organic visible light catalysis The reaction conditions are mild, functional group compatibility is good, and it is suitable for decarboxytrifluoromethylselenidation of complex carboxylic acids This green and efficient strategy is expected to be applied in the design and development of new drugs The main work of this paper was completed by Han Qiuyan, a master of Wuhan University of science and technology, with the assistance of Tan Kaili, a master, and Wang Haonan, an undergraduate This work has been supported by the National Natural Science Foundation of China, the "hundred talents plan" of Hubei Province and the research fund of Wuhan University of science and technology  
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