Metal-Free Annulations Of Ynamides

Ynamide is a kind of alkyne that includes an amide group at one side of the alkynyl.Due to the conjugation between lone pair electrons of the nitrogen atom and the alkynyl,and the regulation of electron-withdrawing group to the alkynyl,ynamide has excellent stability,activity and regioselectivity at the same time.Because of the unique property and structure of ynamide,ynamide is more and more involved in various annulations.Herein,we synthesized 3-amino-δ-carbolines,2-aminoindoles,and phenanthrenes via the annulations of ynamides.As essential nitrogen-containing heterocyclic compounds,3-amino-δ-carbolines and 2-aminoindoles play important roles in various natural products or drugs,such as antibacterial,anti-tumor,anti-inflammatory,anti-anxiety and so on.As important aromatic compounds,fluorenes and phenanthrenes have broad application prospects in the aspects of battery,biology,medicine et al.Therefore,exploring mild and efficient methods to construct these compounds is of great significance for our real life.In this paper,we introduced our work from three aspects.In the second chapter,we firstly constructed 3-amino-δ-carbolines through[2+2+2]cycloadditions between ynamide-nitriles and ynamides.The reaction can be carried out at room temperature,and has the advantages of fast reaction rate,high yield and wide functional group tolerance.More importantly,the method uses environmentally friendly metal-free catalyst TMSOTf and has good regioselectivity.In the third chapter,we firstly used metal-free catalysts to catalyze ynamides and anthranils,which undergoed[3+2]cycloadditions to synthesize 2-aminoindoles.Except high yields,wide functional group tolerance,the reaction also has good regioselectivity.In addition,we also synthesized a variety of 3-alkyl-2-aminoindoles,which enriched indoles’ types.In the fourth chapter,we synthesized fluorenes and phenanthrenes respectively by 5-exo-dig and 6-endo-dig cycloisomerizations of o-alkynylbiaryls using the TfOH.This method has the advantages of fast reaction rate,high yield and broad substrate applicability.We believe that these simple yet powerful annulations will be eagerly adopted into the repertoire of synthetic chemistry.