Synthesis Of Chromone,Chromanone And Pyridone Heterocyclic Compounds By Tandem Cyclization Of Enaminones

As important building block in organic synthesis,owing to their inherent rich reactivity,enaminones have been broadly used in the synthesis of diverse organinc molecules,especially the important application in the synthesis of heterocyclic compounds.The research work of this thesis is enaminone participated tandem cyclization reactions for heterocyclic compounds,including chromones,chromanones and pyridines,which is constituted in three sections.The first section,annulation of enaminones and C-H functionalization of chromones synthesize 2-（N-heterocycle）substituted chromone.By using Cu I as catalyst in the presence of moelular iodine and Ph I（OAc）₂,the synthesis of2-（N-heterocycle）functionalized chromones is accomplished via the reactions of o-hydroxyphenyl enaminones and azoles.The main transformations of annulation and selective vinylβ-C-H heterocycle functionalization in enaminones are involved,which affords new method for the synthesis of 2-nitrogen functionalized chromones.The second section,tandem cyclization and dihalogenation reactions of enaminones for the synthesis of 3,3-dihalochromanones.Starting from o-hydroxyphenyl enaminones and NXS（X=Br or Cl）,the cyclization and dehalogenation of the reactants take place under microwave irradiation,and lead to the synthesis of 3,3-dihalochromanones without using any catalyst or additive.The work further expands the application of enaminones in the area of heterocycle synthesis.The third section,tandem cyclization of enaminones and acryloyl chloride for3,4-dihydropyridone synthesis.With NH₂-functionalized enaminones and acryloyl chloride as substrates,the synthesis of 3,4-dihydropyridones is achieved at room temperature via tandem N-acylation and intramolecular Michael addition process.The reactions are conducted in acqueous THF medium with simple Al Cl₃ as catalyst,which are of high atom economy and promise in synthetic application.