Research group of Professor Yang Song of Guizhou University: methylation and formylation of CO2 and amines catalyzed by bio based ionic liquid

The author of the paper: Dr Zhao Wenfeng's CO2 is considered to be the main substance causing the greenhouse effect, and it is a trend of sustainable development to transform it into high value-added compounds CO2 is very stable in thermodynamics and kinetics At present, the chemical fixation of CO2 is mainly realized by the construction of C-C, C-O and C-N bonds The reaction conditions for the methylation and formylation of CO 2 with amines by constructing C-N bonds are relatively mild, and the nitrogen-containing compounds obtained are widely used in chemical solvents and pesticide synthesis At present, the construction of C-N bond catalyst system mainly involves strong alkaline metal salt, homogeneous non-metal salt and traditional imidazolium salt ionic liquid, but it is difficult to reuse the catalyst in these systems Using silane as the hydrogen source of C-N bond can make the reaction conditions more warm and easy to operate Recently, Professor Yang Song's research group of Guizhou University used biomass based ionic liquid as catalyst (scheme 1) to catalyze the methylation and formylation of CO 2 with amines under mild conditions This work was published on Green Chemistry (DOI: 10.1039 / c8gc03549k) In addition, the research group also used silane as hydrogen source for biomass conversion reaction before, and relevant work was published in green chemistry, communications chemistry, ACS Sustainable Chemistry & Engineering and other journals (source: Green Chemistry) the reaction system has good substrate universality and good activity for a variety of aromatic amines with different substituents In addition, the selectivity of the products in the reaction system was well controlled Only by determining whether to add solvents and reducing the reaction temperature, the high selective conversion of the products into methylamine or formamide was realized The results show that the solvent has a great influence on the activity and selectivity of the reaction, which is mainly due to the difference in the polarity of the solvent (Figure 2) (source: Green Chemistry) next, the author studied the binding mode of silane, CO2 and catalyst by NMR experiment, and proved the possible products or intermediates in the dynamic process of reaction by gradient experiment (Figure 4) Based on the above experimental results, the author proposed a possible reaction mechanism (scheme 2) The author further analyzed the results of NMR experiments, and found that with the extension of time, the content of the substrate decreased gradually, while the formylation products increased first and then decreased, but the methylation products increased gradually with the decrease of the substrate and formylation products Based on this, the author further infers that n-ch3 may be formed by b-path (source: Green Chemistry) further, the author verified the inference results by density functional theory (DFT) calculation (Figure 5) When the reaction is carried out in route a, the required activation energy is higher than that in route B, so it is easier to carry out the reaction in route B In comparison with DFT calculation with or without catalyst, it is found that the catalyst can greatly reduce the activation energy of the reaction, which proves that the catalyst plays an important role in the system (Figure 6) (source: Green Chemistry) a series of nontoxic and highly active bio based ion catalysts were prepared and used in the methylation and formylation of CO 2 and amines The reaction also showed good activity when it was magnified to gram level The first author of this work is Dr Zhao Wenfeng of Guizhou University, and the corresponding authors are Professor Yang Song and Associate Professor Li Hu of Guizhou University This work is supported by NSFC, Huo Yingdong Education Fund and Guizhou science and Technology Fund Committee In addition, we also want to thank the computer network information center of Chinese Academy of Sciences for theoretical calculation.