Synthesis Of Nitrogen-Containing Heterocyclic Compounds Via Cascade Reactions Of Activated Enones

Nitrogen containing heterocycle are the most abundantly available heterocycles in nature,there occupy pivotal positions in chemical and many reated industries such as pharmaceutical,materifals and fine chemicals.Heteroatom activated enones such as enaminones and ketene dithioacetals are useful synthetic building blocks,the divergent reactive sites in these enones can be used to design various organic reactions toward diversity-and target-oriented synthesis.The main contents of this thesis are the application of heteroatom activated enones,including enaminones and ketene dithioacetals in the synthesis of N-containing heterocyclic compounds,including pyrazolines,pyrazoles,quinolines,pyridines by means of new tandem reactions.Four different research works are mainly included.The first section,tandem reactions for the synthesis of pyrazolines in water medium.We utilized water as solvent and acetic acid as additive and realized the tandem reaction of enaminones and sulfonyl hydrazines under mild condition.Based on the construction of two new C-N and a new C=N bonds,a simple and practical green route to the synthesis of pyrazolines is provided.The second section,synthesis of pyrazoles via the tandem reactions of ketene dithioacetals and sulfonyl hydrazines.On the basis of previous work of pyrazoline synthesis,we employed ketene dithioacetals as alternative enone substrates to reaction with sulfonyl hydrazines.By means of further screening the acid catalyst and solvent,the selective synthesis of isomeric pyrazoles with substituents in different positions are achieved.The third section,enaminone-based Povarov reactions in the selective synthesis of 2,3-disubstituted quinolines.By employing enaminones,aldehydes and amine as starting materials,the three-component synthesis of 2,3-disubstituted quinolines is executed in the co-catalysis of Cu I/Tf OH.Unlike the 2,4-disubstituted quinolines provided by conventional Povarov reaction employing terminal alkynes and alkenes,the present work provides quinolines with 2,3-disubstitution,thus paves new way to the synthesis of diversified quinolines.The forth section,pyridine synthesis with three-component reactions of different enaminones and aldehydes.In this work,we employed NH2 and N,N-disubstituted enaminones as two different substrates to react with aldehyde,which enables the three-component tandem synthesis of polysubstituted pyridines by Cu I catalysis.The reactions allow the formation of two new C-C and one C-N bond to provide a new approach for the synthesis of 2,3,5,6-tetrasubstituted pyridines.