Study Of Cascde Reaction With Alkyne-Tethered Diazo Compounds For The Synthesis Of Heterocyclic Compounds

Diazo compounds,which are normally used as carbene precursors,are versatile and powerful reagents,and have been extensively applied in modern synthetic organic chemistry.The carbene/alkyne metathesis(CAM)transformations have recently received considerable attention as a new approach for the construction of diverse polycyclic compounds.This paper mainly focuses on three different types of catalytic approaches,including copper-catalysis,themolysis,and gold-catalysis,for the develoment of novel carbene/alkyne metathesis(CAM)cascade reactions,and construction of heterocycles with structural diversity.Part Ⅰ:(1)We have developed a novel Cu-catalyzed cascade reaction of alkynyl-tethered a-iminodiazoacetates,which provides a general access to both multi-substituted and fused pyrroles in high yields with broad substrate scope.Mechanistically,the y-imino carbene is proposed as the key intermediate in this divergent reaction,which is generated from Cu-catalyzed carbene/alkyne metathesis.In addition,the proposed intermediates in the mechanism are isolated and verified by design of substrates with specific structure.Part Ⅱ:A general and unprecedented thermally induced[3 +2]cycloaddition/carbonyl rearrangement cascade reaction has been developed that provides a general access to fused lactam derivatives in high to excellent yields with broad substrate scope.Mechanistic studies indicate that the 3H-pyrazole is the key intermediate in this cascade reaction,which is confirmed spectroscopically for the first time.Part Ⅲ:This part has disclosed an unprecedented gold-catalyzed carbocyclization reaction of alkyne-tethered diazo compounds,which initially selective activates the alkyne part instead of the diazo group to form the vinyl cabene intermediate,and novel transformations have been developed by interception of this intermediate.Notably,the high selectvity could be realized by this novel approach in carbene/alkyne metathesis(CAM)cascade reactions by avoiding the potential side reactions arise via the direct carbenoid formation with the coexisting diazo group.