Studies On The Reactivity Of α-Diazo Iodonium/Sulfonium Reagents And Halodiazirines

Diazo compounds possess multiple reaction sites and diver sereaction modes.Therefore,diazo compounds are widely studied and applied in the field of pharma ceutical chemistry and material science.At present,a plethora of reactions have been developed based on the properties that the diazo compounds serve as carbon nucleophiles,1,3-dipolar,free carbene,and metal carbene precursors.The development of new reaction systems and new diazo reagents is of great academic significance and practic al value for further broadening the type of reaction and improving the synthetic potential of diazo compounds.Theα-diazo iodonium/sulfonium salts are versatile reagents that can be used as the precursor of radical,cationic carbyne equivalent,and free carbyne radical.In addition,halodiazirines are three-membered ringisomers of the diazo compounds and are carbynyl cation equivalents to achieve the transformations that distinguish them from carbene interme diates.However,research on the above two types of reagents is very limited.This paper focuses on the reactivity ofα-diazo iodonium/sulfonium reagents and halodiazirines.The paper is divided into four chapters,and the main contents are summarized as follows:（1）Recent progress in new strategies of diazo compound transformations and the reactions involving new diazo reagents and halodiazirines are reviewed.（2）A novel NHCs-catalyzed process for the synthesis of 1,3,4-oxadiazoles from readily accessible aldehydes by combining the nucleophilicity of the putative Breslow intermediate and the inherent electrophili city ofα-diazo iodonium triflate is developed.The reaction proceeds under mild conditions with a wide range of functional group tolerance.The gram-scale reaction and the follow-up chemistry were performed to elaborate on the utility of this method.It is explained by the mechanism experiment thatα-diazo ammonium triflate is the active species of the reaction,and a possible reaction mechanism is proposed.（3）A convergent synthesis of tetrasubs tituted furans is achie ved through three-component co upling of aryl alkyn es,α-diazo sulfonium triflate,and TMSCN under the photoredox condition.Cu（dap）₂Cl is chosen as the optimal photocatalyst.The reaction proceeds under mild conditions with high functional group tolerance.A variety of substituted alkyne substrates andα-diazo diazonium salt reagents can serve as the reactant smoothly.The gram-scale synthesis is successfully achieved by using a continuous-flow photoreactor.A series of follow-up transformations are conducted to illust rate the synthetic utility.The radical capture experiment proved that the radical intermediate is likely to be involved in the mechanism.Finally,there action mechanism was proposed based on a series of mechanism experiments.（4）A versatile ring expansion reaction of indenes enabled by halodiarines through the generation of aryl carbynyl cation intermediate was demonstrated.The reaction shows wide substrate applicability and gram-scale synthesis can be achieved smoothly.The reaction may go through the ring opening/aromatization process of the cyclopropane cation intermediate.