Synthesis Of Nitrogen-containing Heterocyclics Promoted By Transition Metals Or Nonmetals

Nitrogen-containing heterocycles account for a large proportion of heterocycles.It widely exist in the all kinds of natural products and drug molecules,which have extremely important application value in the fields of organic synthesis,catalysis,medicine,materials,pesticides and so on.Not only is copper widely used in synthesis because of its different oxidation valence states,but also it is cheep and has great prospects.As one of the reagents with simple structure and stable property in organic chemistry,iodine plays an important role in green chemistry due to its low cost and easy operation.This dissertation focuses on the synthesis of nitrogen-containing heterocycles promoted by copper,iodine and base.The following works are mainly described:1.We have developed a method for the synthesis of diverse multifunctionalized dihydropyrazoles through copper-mediated formal[4+1]cycloaddition reaction of readily available N-sulfonylhydrazones and sulfoxoniumylides.This reaction has the advantages of good regioselectivity and functional group compatibility.It can be used for gram reaction.The starting material is cheap and easy to obtain,and the operation is simple.It provides a simple and convenient method for the synthesis of dihydropyrazole compounds.2.We have developed a multicomponent reaction for the construction of 3-sulfenylimidazo[1,2-a]pyridines from 2-aminopyridines,ketones,and sulfonyl hydrazides.The method can avoid the use of toxic and pungent thiophenol and Mercaptan,and the operation is simple.This method can easily carry out the reaction at the gram level,and provides the possibility for the future industrial use.3.We have developed a strategy synthesis of 5-trifluoromethyl-1,2,4-triazoles from iodine-mediated annulation of trifluoroacetimidoyl chlorides and hydrazones.The method is characterized by mild reaction conditions,simple operation,wide substrate range and high efficiency.The transformation provides a simple and efficient method for the synthesis of trifluoromethyl substituted 1,2,4-triazole.4.We have developed an efficient approach for the preparation of 5-trifluoromethyl-imidazoles through base-mediated[3+2]annulation of active methylene isocyanides with trifluoroacetimidoyl chlorides.This method can easily introduce trifluoromethyl group into the product and construct two C-N bonds efficiently in one step without any metal catalysts and ligands.The reaction features simple conditions,good yields and the high atom-economy,which provides a green and efficient method for the synthesis of 5-trifluoromethyl imidazole compounds.