Application Of Diazo Compounds In Organic Synthesis

Due to their unique structure and various resonance forms,diazo compounds have rich and varied reactivity.Therefore,diazo compounds are very important intermediates in organic synthesis and have been widely used in organic chemistry,natural product chemistry and material chemistry.Although a variety of diazo compounds have been widely used in the synthesis of important molecules in this field,the preparation of diazomethyl radicals and the application ofβ-hydroxy-α-diazo compounds in organic synthesis are rarely studied.In this paper,the photocatalytic reaction ofα-diazosulfonium andβ-hydroxy-α-diazo compound to diazomethyl radical and the coupling reaction ofβ-hydroxy-α-diazo compound with vinyl azides were studied.The specific research of this paper is as follows:1.Visible light induced[3+2]cyclization reaction betweenα-diazosulfonium and terminal alkyneA series of 3,5-disubstituted 1H-pyrazoles have been prepared by the[3+2]cyclization reaction of diazomethyl radical withα-diazosulfonium as an important intermediate under visible light irradiation.The reaction has the advantages of mild reaction conditions,no photocatalyst and chemical oxidant,high regional selectivity and wide range of substrates.This reaction not only provides a new method for the synthesis of pyrazole compounds,but also lays a foundation for the application of diazomethyl radical in organic synthesis..2.Study on the coupling reaction ofα-substituted vinyl azides andβ-hydroxy-α-diazo carbonyl compoundsUsing Sc（OTf）₃ as catalyst,vinyl diazonium cations generated fromβ-hydroxy-α-diazo carbonyl compounds were used as key intermediates,and vinyl azides were used as carbon nucleophile to successfully conjugate vinyl azides andβ-hydroxy-α-diazo carbonyl compounds,and a series ofγ-carbonyl substituted diazo compounds were synthesized.This method not only provides a new method to synthesizeγ-carbonyl substituted diazo compounds,but also provides a new idea for the further application ofβ-hydroxy-α-diazo carbonyl compounds as vinyl diazonium cations in synthesis.