Zhang Sheng and Xu Kun realized the internal fatty reaction of carboxylic acid under the condition of electrochemistry

Due to the research of Kolbe in the field of carboxylic acid electrolysis (Kolbe reaction), the application of electrochemistry in organic synthesis has gradually attracted people's attention, and has gradually developed into a new discipline of mechanochemistry With the increasing chemical pollution in the modern industrial generation, people put forward higher requirements for organic synthesis in the 21st century, that is, to meet the standards of green chemistry As a new interdisciplinary subject, mechanochemistry has special advantages in this respect: in the reaction, electrons are used as a clean reagent to realize the oxidation-reduction process; in addition, electrochemical reaction theory can The reaction of δ g > 0 was realized It is precisely these advantages that many outstanding international research groups, including P S Baran, S S Stahl, L Ackermann, have turned their attention to the study of electromechanical chemistry Recently, Dr Zhang Sheng and Dr Xu Kun of the school of chemical engineering of Nanyang Normal University have made a breakthrough in their electrochemical catalysis research Dr Zhang Sheng and Dr Xu Kun graduated from the University of science and technology of China, under the guidance of Professor Wang Zhiyong, an expert in mechanical and electrical chemistry in China Since their independent research, the research direction mainly involves electrochemical catalysis, photochemical catalysis and green chemistry The research achievements have been listed in the cover articles of the top journals chemical communications and green chemistry for many times Source: as an important structural framework, lipid compounds are widely distributed in bioactive molecules and drugs in Nanyang Normal University (Figure 1) Therefore, the construction of internal fat has also been widely concerned, and these methods mostly involve the use of transition metals and some strong oxidants, and the low reaction efficiency generally requires high temperature or long reaction time, which greatly limits the practical application of these methods Fig 1 Bioactive endolipid compounds (source: organicletters) according to one or two kinds of endolipid compounds with different structural characteristics in Fig 2, Zhang Sheng and Xu Kun team adopted two different electrochemical strategies (Fig 2): direct electrochemical oxidation to achieve the internal lipid reaction of SP 2 & SP 3 C-H; indirect electrocatalysis to achieve the internal lipid reaction of γ - acylic acid In these two electrochemical internal lipid reactions, the use of metal and oxidant is avoided, more importantly, the reaction is more efficient, most of the reactions are completed in 1.5-3 hours, and the reaction can be easily enlarged to more than tens of grams Figure 2 Electrochemical construction of internal lipid compounds (source: organicletters) In the direct electrooxidation of internal lipid, a series of internal lipid structures can be constructed by using only tetrabutyl tetrafluoroborate as electrolyte (Table 1) As shown in Table 1, the reaction has a good range of substrate application, it is worth mentioning that the substituent (2j-2l) can selectively lipoplate in the substituent, thus giving the target product Table 1 The range of biaryl endolipid substrates (source: organicletters) Then, the author studied the more challenging endolipid reaction of SP 3c-h (Table 2) As shown in the following table, the reaction can selectively generate SP 3 C-H internal lipid compound, and no ring closing product of SP 2 C-H has been detected in the reaction In addition, the third-order sp 3c-h was also suitable for the reaction (6g - 6K) It is worth mentioning that due to the low oxidation potential, the fatty acid phenylbutyric acid is prone to the side reaction of electrochemical decarboxylation, and the yield of 62% can also be obtained under the standard conditions Table 2 The range of fatty substrates in SP 3 C-H (source: Organic letters) After studying the applicable range of substrates, the author studied the practicability of the reaction, and designed the following flow reaction device with Zeng Chengchu of Beijing University of Technology (Figure 3) The substrate is delivered to the reaction cell by peristaltic pump, and the conversion of 40g raw material is completed in about 200ml reaction cell within six hours The final product can be obtained with purity of > 97% through simple washing treatment Figure 3 Flow reaction device (source: organicletters) in the indirect electrocatalytic internal lipid reaction of halogen, we used 15 mol% tetrabutylammonium iodide as catalyst to construct the following internal lipid compounds (Table 3) The reaction has good tolerance for electronic effect and steric resistance effect (2A - 2O) For the substrate (2S) with two reaction potentials, a single five component internal lipid product can be obtained In addition, a variety of spiro ring chiral molecules can also be constructed efficiently (2W - 2x) Table 3 The two research results of the constructed endolipid compounds (source: Organic letters) were published on organic letters, and the research was supported by the National Natural Science Foundation of China (No: 21702113, 21602119, u1504208) Original link: 1 Http://pubs.acs.org/doi/10.1021/acs.orglett.7b03617 2 Http://pubs.acs.org/doi/10.1021/acs.orglett.7b03333 Nanyang Normal University School of chemical and pharmaceutical engineering home page: http://www2.nynu.edu.cn/yunxi/huaxue/index.html