Studies On The Photo-induced Cycloaddition Synthesis Of Halogenated Spiro[4,5]trienones

Photo-induced cycloaddition synthesis of halogenated spiro[4,5]trienones of N-aryl alkynamides have been investigated.In section one,the photo-induced synthesis halogenated spiro[4,5]trienones from N-aryl alkynamides with hypervalent iodine reagent PhI?OCOCF₃?₂ was developed.Firstly,the hypervalent iodine reagent PhI?OCOCF₃?₂ was used as the iodination reagent,and the reaction parameters were screened.The optimal reaction conditions were determined as 2.0equiv PhI?OCOCF₃?₂,2.0 equiv NaOAc in acetonitrile,irradiation of the xenon lamp at room temperature under an oxygen atmosphere for 18 h.Subsequently,we investigated a photo-induced brominated spirocyclization and chlorinated spirocyclization with PIFA and KBr/KCl as sources of halogen radical.The reagent amount,solvent,and reaction time were screened to determine the optimal reaction conditions:1.5 equiv PhI?OCOCF₃?₂,2.0 equiv KBr/KCl,2.0 equiv NaOAc in acetonitrile,irradiation of the blue LED at room temperature for 2 h.Having identified the optimal reaction conditions for halogenated spirocyclization of N-aryl alkynamides,we investigated the substrate scope.Therefore,this method has the advantages of mild reacting condition without using transition metals photosensitizer and good tolerance of functional groups.Section two focuses on the photo-induced synthesis halogenated spiro[4,5]trienones from N-aryl alkynamides of 1,3-dihalo-5,5-dimethylhydantoin as a halogenation reagent.Firstly,the brominated spirocyclization of N-aryl alkynamides with DBDMH was selected as a model to screen the reaction parameters.It was determined that the optimal reaction conditions:0.6equiv DBDMH,2.0 equiv NaOAc in acetonitrile and irradiation of the blue LED at room temperature for 12 h.Chlorinated spirocyclization of N-aryl alkynamides used DCDMH as chlorinating reagent.The optimal reaction conditions were determined as 1.2 equiv DCDMH,1 mol%Eosin B as the photosensitizer,3.5 equiv tert-butyl hydroperoxide,2.0 equiv NaOAc in acetonitrile and irradiation of the blue LED at room temperature for 18 h.Under the optimal conditions,the substrate scope was examined.The N-aryl alkynamides substituted with alkyl and aryl,and phenyl 3-phenylpropiolate,proceed smoothly.Therefore,a cheap,efficient,and mild reaction was achieved without using transition metals photosensitizer.