Study On Hydrogen Transfer-mediated Synthesis And Functionalization Of Quinolines By Heterogeneous Catalysis

Quinolines and its derivatives exist widely in nature,and are often used to develop high-value products related to People's Daily life,including energy,medicine,functional materials,bioactive molecules and argochemicals,sensors,dyes,etc.Therefore,it is of great scientific and practical significance to develop efficient and selective methods for the construction and structural modification of quinolines,which not only provide the possibility to realize the synthetic diversity of quinoline derivatives,but also lay a material foundation for the further development of novel biological and pharmaceutical active molecules,materials and other functional products.In addition,the development of some green and sustainable catalytic technologies has become an important research direction in the field of organic synthesis under the current situation where the resources and environment are becoming increasingly tense.In contrast,heterogeneous catalysis can better fit these development directions.Based on these points,we have developed several new methods for the synthesis and structural modification of several quinoline derivatives using supported metal nanocatalysts through hydrogen transfer-mediated coupling strategy.The specific contents are as follows:(1)In Chapter 2,by developing a new type of cobalt-based nanocatalytic material CoO_x/N-Si-TiO₂,it was successfully applied to achieve the hydrogen transfer-mediated?-C–H dialkylation of 2-alkylquinoline derivatives with various aldehydes in the presence of formic acid as the hydrogen donor.This catalytic synthetic method can directly construct various functionalized 2,3-dialkylated quinoline compounds,proceeding with good substrate universality,high regio and chemoselectivity,cost-effectiveness,easily available and reusable catalyst,and generation of water as the by-product.The current work demonstrates the potential for direct functionalization of C–H bonds by combining the design of a heterogeneous catalyst with the reductive dearomatization as an activation mode of inert N-heteroarenes.(2)In Chapter 3,we have developed a new N-doped Zr?O₂@C supported cobalt nanocatalytic material and applied it to the hydrogen transfer cyclization reaction between2-nitroarylcarbonyl compounds and alkynyl ester or alkynone.The reaction provides a new synthetic method for the construction of quinoline ester derivatives,which features good functional group tolerance,high chemoselectivity,easy reusability of the catalyst,and operational simplicity.The current work lays a foundation for the development of heterogeneous catalysts with suitable carriers and further application in the development of hydrogen transfer-mediated construction of various quinoline compounds.(3)In Chapter 4,we developed a new bifunctional catalyst(Ir/N-Si-TiO₂)composed of nitrogen-silicon-doped TiO₂ carrier and iridium nanoparticles.By using this catalyst,the hydrogen transfer-mediated mono-alkylation and dialkylation of quinoline derivatives with various salicylaldehydes or o-aminobenzyl alcohols have been realized.A variety of6-alkyltetrahydroquinoline and 6,8-dialkylated tetrahydroquinoline compounds were synthesized with this catalytic transformtion.It features broad substrate scope,recyclable catalyst,and the generation of water as the sole by-product.This present work has laid a foundation for further development of more valuable chemical transformations by combining heterogeneous catalysis and reduction coupling.(4)In Chapter 5,by utilizing a commercially available palladium/carbon catalyst system,we have realized a hydrogen transfer-mediated cyclization reaction of resorcinol and2-nitroaromatic aldehyde,providing a new synthetic method for the preparation of acridinone derivatives.The acridone derivatives obtained by this protocol also provide the potential for further development of functional products including pharmaceutically active substances and optoelectronic materials.In addition,the catalytic transformation has the advantages of operational simplicity,easily available catalytic system,and no need for pre-installation of specific coupling agents.Moreover,the current work also provides the potential for further conversion of renewable resources into high-value products.In conclusion,the research work of this thesis has achieved four new catalytic approaches on the construction and structural modification of quinoline derivatives by developing compatible heterogeneous catalyst systems and utilizing hydrogen-transfer-mediated coupling strategy.These researches have laid the foundation for further development of green,efficient,and selective reductive coupling reactions by hydrogen transfer-mediated activation mode of inert substances,have achieved some synthetic purposes that are difficult accessible with homogeneous catalysis,and have enriched the connotation of green catalysis and organic synthetic chemistry.