Study On The Activation Of Inert Chemical Bonds Promoted By Alkyl Nitrites

In this thesis,t-butyl nitrite promoted polyfunctionalization of piperidines and carbon-carbon cleavage of piperazines were fully investigated.Furthermore,NaNO2 was employed as the oxidant to trigger the C-H oxidation of piperazines,synthesizing a series of nitroolefins in high yields.The details are listed below:(1)Efficient cascade ?,?3-sp3 C-H bond difunctionalization and C-N bond activation of N-aryl azacycles have been realized using TBN as a metal-free oxidant,constructing aldehyde,N-nitroso and oxime functionalities in one synthetic step.Compared with the reported C-H and C-N bond activation,this reaction is superior in higher functional group tolerance,wider reaction scope and higher reaction efficiency(10-78%yields).Over 33 substrates were investigated as well as further functionalization of the generated products,highlighting the potential applications of this reaction.The obtained products were fully identified by 1H NMR,13C NMR and HRMS.According to the results of the control experiments,a possible mechanism was proposed to rationalize the product formation.(2)TBN enabled C-C bond activation of N-aryl piperazines was realized,providing a series of formamide derivtatives in high yields.Compared with other catalyst systems,this metal-free reaction is superior in milder reaction conditions,in which dioxygen is employed as the green oxidant,avoiding the overuse of excessive amounts of other oxidants.The evaluation of the reaction scope shows that various functional groups can be well tolerated without loss of the reaction efficiency.Over 25 C-C bond cleaved products were obtained,which were characterized by 1H NMR,13C NMR and HRMS.According to the results of control experiments,a radical mediated mechanism was presented.(3)Nitroalkenes are one of important organic building blocks.Generally,such compounds are synthesized from unsaturated compounds.Herein,we provided a new approach to prepare nitroalkenes from N-aryl piperazines,using sodium nitrite as the oxidant as well as nitrating reagent.This reaction proceeded through a free radical sp3 C-H oxidation in the presence of acidic additive,providing a series of nitroalkenes in high yields.The mild and metal-free reaction conditions highlight the applications in preparation of functionalized nitroalkenes.Besides,this reaction exhibits good functional group tolerance and high reaction efficiency.Over 26 nitroalkenes with various substituents were synthesized,and all of the obtained products were fully characterized by 1H NMR,13C NMR and HRMS.Based on the control experiments,a plausible mechanism was proposed,in which a free radical intermediate was involved.