Synthesis Of Nitrogen-containing Heterocyclic Skeleton From Diazo Compounds

Diazo compounds have a long history of useful applications in organic chemistry,which can be induced to undergo a wide variety of chemical transformations under very mild conditions.Of particular note,diazo compounds can be decomposed by transition metal complexes to generate highly active metal carbene intermediates,which can subsequently undergo diverse transformations,including cyclopropanation,X-H(X=C,O,S,N,etc.)insertion,ylide formation.Because of its privileged chemical properties,diazo compounds have become star molecules in organic synthesis,especially in the construction of carbocyclic or heterocyclic compounds.This thesis mainly focuses on the methodology of facile and efficient synthesis of nitrogen-containing heterocyclic compound from diazo compounds.The research findings are showed as followed:Part one:an unprecedented radical-carbene coupling reaction between aromatic amines and diazo compounds was well developed,which afforded a bridge connecting between radical chemistry and metal carbene chemistry.This Mn-catalyzed tandem reaction also provided a fundamentally different and practical approach to the indole skeleton under mild conditions.The mechanistic investigations(the radical trapping experiment and cyclopropanation experiment)provided unambiguous evidence for the involvement of ?-amino alkyl radical and carbene intermediate.An electronic preference experiment with equal amounts of 4-methyl-and 4-fluoro-N,N-diethylaniline suggested that the cyclization step involved electrophilic aromatic substitution.Part two:we have demonstrated a copper-catalyzed three-component reaction affording fully substituted 1,2,4-triazoles from diazonium salts,diazo compounds and nitriles in moderate to high yields.This reaction provides a simple and efficient strategy to construct structurally diverse 1,2,4-triazoles from readily available starting materials.The other salient feature of this approach is the convenient introduction of three different substituents in a one-step fashion.The preliminary experiment and theoretical calculations results show that the process might through[3+2]cycloaddition of diazonium salts and nitrile ylide intermediates,and diazonium salts provide the two nitrogen atoms to the target skeletons.Part three:Aryl diazonium salts were originally introduced into organic synthesis as efficient catalyst.A simple aryl diazonium salt-catalyzed 1,3-dipolar cycloaddition/N-H insertion tandem reaction of diazocarbonyl compounds and alkynes to synthesize poly-substituted pyrazole derivatives has been achieved.The process is simple and can be used to generate a wide range of functionalized pyrazoles.Particularly,pyrazole derivatives bearing an alkenyl or alkynyl group could also be prepared in synthetically acceptable yields,with the unsaturated C-C bond intact,which would enable the introduction of greater molecular complexity.