Research On The Application Of CO₂ As A C1 Resource In The Synthesis Of Heterocycles

In recently years,carbon dioxide content in the atmosphere has become a major cause of the greenhouse effect.However,carbon dioxide has many excellent characteristics as an available C1 resource.In the environmental protection,society and economy development,using carbon dioxide to synthesize high-value added chemicals has been attracting much attention all over the world.The main approcach that utilizing carbon dioxide of chemical transformation is mainly through the activation of carbon dioxide and transforms it into active functional group.In accordance with the state of carbon dioxide to achieve a variety of reduction,such as conversion to methyl,acyl,and carboxyl,and so on.In this way,the efficient use of carbon dioxide can be achieved,which is in line with the development trend of the times.Methylamines and formamides are widely present in natural products and drug molecules.Using carbon dioxide to synthesize such products can achieve high value.In this paper,a case of the selective methylation and formylation of amines catalyzed by organic small molecule DBU using carbon dioxide as a C1 block,polymethylsilyloxysilane(PMHS)as a reducing agent is described.The reaction system is a homogeneous reaction system,and the reaction can be achieved with a very low amount of catalyst.At the same time,the reducing agent polymethylsiloxy alkane(PMHS)used in the reaction is an extremely inexpensive reagent,which is safe and easy to operate compared with hydrogen.Moreover the catalyst DBU involved in the system is a very common organic base in the laboratory.It is insensitive to water and oxygen and can be stable in air.Finally,we have developed a selective organocatalytic N-methylation and N-formylation of amines for the synthesis of methylamines or formaides using CO2 as a sustainable C1 source and polymethylhydrosiloxane(PMHS)as a reductant.Carboxylic acid is a very common product in all kinds of chemical reagents,and they even exist in many natural compounds.The compounds containing carboxyl groups have strong biological activities in natural products and drugs,and have important functions in increasing the carbon skeleton and performing derivatization synthesis in terms of chemical synthesis and transformation.Compounds containing a C-N bond are also a very broad class of compounds and it is difficult to achieve derivatization reactions by cleaving inert C-N bonds.In recent years,many coupling reactions researchs based on cleavage of C-N bonds have been reported,in which quaternary ammonium salts are widely used.Quaternary ammonium salts contain highly activated C-N bonds.Therefore,we use quaternary ammonium salts and carbon dioxide as raw materials to develop a new carbon dioxide carboxylation reaction system through the C-N bond cleavage reaction under the transition metals.