Visible-light-induced Decarboxylative Hydrazination And Oximation Of Carboxylic Acids

As a green,clean and sustainable energy source,visible light is simple to operate,natural abundant,low cost,and has great potential for application in many fields.In recent years,modern organic photosynthesis has developed rapidly as a powerful and green synthesis strategy.Visible-light-induced photochemical reactions have the advantages of mild reaction conditions,simple operation,good chemical selectivity and functional group compatibility.Therefore,the visible-light photocatalytic mode reactions are highly favored by organic synthesis workers.Carboxylic acids are one of the most abundant raw materials on earth.They are readily available,inexpensive,stable and non-toxic,making them important raw materials for"green synthesis".Carboxylic acids could be converted to their corresponding free radicals by photoinduction and are widely used in organic photosynthesis.However,visible-light-induced decarboxylative hydrazination and oximation of carboxylic acids have not been reported.Therefore,based on the full investigation of literature,the visible-light-induced decarboxylative hydrazination and oximation of carboxylic acids have been systematically studied in this thesis,establishing the mild,green and novel methods.The main research content of this thesis includes the following two parts:Part I:Visible-light-induced decarboxylative hydrazination of alkyl carboxylic acidsThe decarboxylative hydrazination of alkyl carboxylic acids with azobenzenes(or hydroalkylation of azobenzenes)is a potential and direct way for the synthesis of N,N’diaryl trisubstituted hydrazines.We designed a visible-light-induced strategy to systematically study the decarboxylative hydrazination of alkyl carboxylic acids with azobenzenes.Using commercially available Mes-Acr+ClO4-as an organic photocatalyst,the reaction proceeds smoothly at room temperature under visible light irradiation.Various substituted symmetric and unsymmetric azobenzenes and a variety of functional group-substituted alkyl carboxylic acids tolerated well,affording N,N’-diaryl trisubstituted hydrazines with good to excellent yields.CO2 is the only by-product.The reaction have advantages of mild conditions,wide substrate scope,good functional group tolerance and high yields.This work not only realized the visible-light-induced hydroalkylation of azobenzenes for the first time,but also provided a new mild and green way for the preparation of trisubstituted hydrazines.Part II:Visible-light-induced decarboxylative oximation of N-aryl glycinesWe have explored the decarboxylative oximation of N-aryl glycines with tert-butyl nitrite by visible-light-induced strategy.It is found that most of N-aryl glycines could react under direct irradiation by visible light at room temperature without any photocatalysts to obtain the corresponding α-aminoximes.For some of the substrates which could not react under direct visible light irradiation,the target products could also be obtained by photocatalysis.In general,a variety of substituted N-aryl glycines were converted into the corresponding decarboxylated oximation products with acceptable yields.The developed new method has mild conditions and good functional group tolerance,which opens up a facile and sustainable way for the synthesis of novel α-aminoximes.