Exploratory Research On Sulfur Dioxide Downstream Product Diaobaifen In The Synthesis Of Heterocycles

With the sustained and rapid development of China's economy,environmental pollution has become increasingly serious.The most prominent environmental pollution problems are haze and acid rain,which pose a serious threat to China's economic production and the physical and mental health of residents.One of the main causes of haze and acid rain is the excessive emission of sulfur dioxide.At present,the main methods to control sulfur dioxide are desulfurization treatment and absorption method,but their efficiency is usually relatively low,and they also need to invest a lot of costs and produce many other wastes,which is the fundamental reason why pollution sources are difficult to control.If we can increase the development of the value of pollutant utilization,turn waste into treasure,and transform it into a product with important economic utilization value,so as to alleviate the related pollution problem to some extent.However,since sulfur dioxide is a gas,it has great difficulty and limitation for its direct development and application.Therefore,the downstream products of sulfur dioxide have received our attention.Rongalite is an important downstream chemical product of sulfur dioxide.It is low in price(about 12,000 yuan/ton)and widely used in industrial production.It can be used as a discharge agent in the printing and dyeing industry,as well as in the polymerization of rubber,sugar and ethylene compounds,etc.However,it is seldom used in organic synthesis.On the other hand,heterocyclic compounds are one of the most important structural units in organic synthesis,and many natural products,pharmaceutically active molecules,multifunctional materials,etc.are all based on heterocyclic compounds.Therefore,it is of great significance and application value to develop efficient synthesis methods of heterocyclic compounds.'Therefore,we hope to build a novel diversity-oriented reaction system(DORS)based on the principle of self-sorting reaction network strategy with rongalite as the core;so as to build a novel heterocyclic framework with rongalite as the substrate.In this thesis,we mainly focus on diversity transformation of rongalite,which is used as a carbon source,sulfur dioxide source,multi-functional reagent and a new oximation reagent system composed with copper nitrate to systematically synthesize the diversified heterocyclic structures.In addition,two novel heterocyclic compounds were obtained based on in-situ capture of o-quinodimethanes.The main contents are as follows:In chapter 1,we investigate and summarize the background of rongalite,its use in industry and its application in organic synthesis.Secondly,we introduced the challenges of modem organic synthesis.Then,according to the existing research status,we proposed our research mentality of this thesis.In chapter 2,based on the multiple sp3 C-H bond functionalization strategy,we developed a method to construct 2,3,5-trisubstituted furan compounds from aryl methyl ketones and rongalite,which has the characteristics of simple operation,high reaction efficiency,mild conditions and a wide range of substrates.In this reaction,the inexpensive industrial product rongalite was inserted into a molecule as a Cl source to synthesize a furan compound and the reaction is an example of a four-component series reaction in the form of a form which has certain application prospects,and this reaction is a formal example of four-component tandem reaction,which may have some application prospect.In chapter 3,based on the multi-component cascade reaction strategy,we developed a method to the synthesis of C3-sulfenylated chromones from o-hydroxyaryl methyl ketones and rongalite.In this reaction,the inexpensive industrial product rongalite was used as a Cl source,and DMSO not only acted as a solvent,but also acted as a thiomethylation reagent to participate in the reaction.In chapter 4,we developed a method to the synthesis of N-aminoarylsulfonamide based on the sulfonylation reaction of rongalite and aryl diazotetrafluoroborate by using rongalite as a radical initiator,a sulfur dioxide surrogate and a reducing reagent simultaneously.Compared to previous methods,this method does not require an external amine source,metals,and oxidants and can be carried out at room temperature.We also use this method to introduce sulfonyl hydrazide groups into natural products and drug candidates containing an aniline backbone,which may have some application prospect.In chapter 5,we developed a rongalite-mediated multicomponent radical annulation reaction for the construction of trisubstituted or fully substituted pyrazoles from aryldiazonium salts as dual synthon and?,?-unsaturated aldehyde or ketone based on rongalite as radical initiator and reducing reagent.Aryldiazonium salts serve as both precursors of the aryl and aryl hydrazine units to participate in the reaction.Compared to previous methods,this method does not require metals and oxidants and can be carried out at room temperature.In chapter 6,we developed a novel and mild oximation reagent system form rongalite and copper nitrate.And this oximation reagent system could realize the direct oximation of the sp3 C-H bonds of o-hydroxyaryl methyl ketones and methyl ketones to afford benzofuran-2,3-ketoxime and thiohydroximic acids.This method avoids the addition of strong acid and strong oxidant,and has good substrate applicability and high yield.It is a green and efficient method for the synthesis of related oxime compounds,which may have some application prospect.In chapter 7,in addition to the main research focus on "the exploration research on the reactions of sulfur dioxide downstream industrial products rongalite to construct heterocyclic compounds",I also studied the work of using benzo[c]oxepines as the precursors of o-quinodimethanes.Based on in-situ capture strategy of o-quinodimethanes,we developed a method to the synthesis of 3-(2-methylbenzyl)indole derivatives form benzo[c]oxepines and indole through tandem C-O bond cleavage/[1,5]H-shift/Michael addition reactions.In chapter 8,based on in-situ capture strategy of o-quinodimethanes,we developed a method to the synthesis of 2-hydroxyl chromans derivatives from benzo[c]oxepines and electron-rich phenols through tandem tandem C-O bond cleavage/Michael addition/annulation reactions.This method provides a novel[3+3]cycloaddition reaction for the synthesis of 2-hydroxyl chromans compounds.In chapter 9,the summary of this thesis and the outlook of future work were given.