Application Of Visible-Light-Induced Wolff Rearrangement In Acyl Transfer And Cycloaddition Reactions

Ketenes,as versatile reactive reagents,are extensively applied to organic synthesis.However,high reactivity makes ketene prone to aggregate,which renders ketene not be easy to prepare in high yield and long-term storage in laboratory.In this PhD thesis,by means of visible-light-induced Wolff rearrangements to generate ketenes in situ,we conducted the research on the catalytic acyl transfer reactions and cycloaddtions with photogenerated ketenes.Firstly,we have developed a visible-light-induced Wolff rearrangement,regio-divergent acylation reaction of β-ketoesters with α-diazoketones as acyl source.In particular,employing Lewis acid catalyst to activate the β-ketoesters or Lewis base catalyst to activate the photogenerated ketene intermediates promote selective C-acylation and O-acylation processes(47 examples,60-99%yields).This protocol shows broad substrate scope and excellent functional group,which could be performed on a gram-scale.Based on control experiments,we also propose a reasonable explanation for the two processes.Moreover,we also have accomplished a visible-light-induced Wolff rearrangement,DBUcatalyzed desymmetric[3+2]cycloaddition reaction of para-quinamines with the photogenerated ketene,affording a wide variety of hydroindole derivatives(34 examples,45-99%yields).This method shows great substrate diversity and functional group compatibility,providing a rapid and efficient access to hydroindole derivatives,which could be further transformed to hydroindoles with potential biological activity.Based on previous reports and control experiments,we propose a plausible mechanism.Finally,by combing gold catalysis and N-oxide catalysis,we have realized a visible-lightinduced sequential catalyzed asymmetric[4+2]cycloaddition reaction of conjugate enynamides withα-diazoketones,providing a wide variety of bicyclic lactam products with good efficiency and excellent diastereo-and enantio-selectivities(78-95%yields,90-98%ee,up to>19:1 dr).Notably,these products could be readily converted into other useful functional molecules.More importantly,the configuration of the intermediate,the product and N-oxide catalyst are confirmed by X-ray analysis.All the products were confirmed by 1H NMR,13C NMR and HRMS characterization,and the representative products were further confirmed through X-ray single crystal analysis.