Investigation On The Construction Of Sulfur-containing Heterocyclic Compounds In Oxidation System Using Non-noble Metal Catalyst

Sulfur-containing molecules are a clss of important molecular framework in organic synthesis,which are widely used in the synthesis of natural products,the study of drug molecules and the performance improvement of material chemistry.From medicine sulfur and black gunpowder in ancient China to penicillin and narfenavir?a protease inhibitor of AIDS?nowdays,thsese compounds are closely related to sulfur.Compared with the traditional cross-coupling reaction between nucleophiles and electrophiles,the emergence of oxidative coupling reaction,which is occurred between two nucleophiles,greatly expands the scope of application of the substrate,and becomes a powerful synthetic strategy in modern organic chemistry.In recent years,transition metal-catalyzed cross-coupling reactions have attracted much attention due to their good chemical and regioselectivity.However,with the continuous improvement of people's living standards,there is a growing voice for an environment-friendly society.Therefore,it is the development direction of green chemistry to use non-noble metal catalysts,low-toxic oxidants,as well as clean and renewable energy-oxygen as oxidants.Thus,this paper studies a new synthesis method of integrating simple sulfur-containing compounds into various organic heterocyclic molecules in the oxidation system using inexpensive transimetal catalyst?copper or iron?.The details are as follows:?1?Copper-catalyzed benzylic C–H functionalization,oxidation and cyclization of methylarenes:direct access to 2-arylbenzothiazoles.Using Cu I as catalyst and peroxy tert-butyl alcohol as oxidant,a series of 2-arylbenzothiazole derivatives can be obtained by benzylic C?sp³?–H amination,oxidation and cyclization of methyl aromatics.The method has available raw materials and wide substrate applicabilities.?2?Copper-catalyzed aerobic oxidative regioselective thiocyanation of aromatics and heteroaromatics.Using potassium thiocyanate as sulfur source,the thiocyanation of aromatic and heteroaromatic compounds?indole,pyrrole,aniline,etc.?with high chemoselectivity and regioselectivity was realized.With cheap and low toxic metal copper as catalyst and green oxygen as oxidant,the method features simple operation,available raw materials and good functional group tolerance.?3?Copper-catalyzed aerobic oxidative[3+2]annulation for the synthesis of5-amino/imino-substituted 1,2,4-thiadiazoles through C–N/N–S bond formation.Through the formation of C–N/N–S bonds in one step,copper-catalyzed cyclization of2-aminopyridine/amidine with isothiocyanate was realized,and various 5-amino/imino substituted pyrrolidine/imino 4-thiadiazole derivatives were obtained.This method has demonstrated high reactivity,mild reaction conditions,and a broad substrate scope.?4?Restriction of conformation transformation in excited state?RCTES?:a feasible strategy for aggregation-induced emission building block based on stable exocyclic C=N group in heterocyclic compounds.In this work,taking[1,2,4]thiadiazole[4,3-a]pyridine?TZP?derivatives as an example,a novel and feasible strategy for the construction of AIE unit based on E-Z isomerization?EZI?of exocyclic C=N double bond is proposed.It is believed that as a potential building block for AIEgens with special heterocyclic structure.These findings would open up opportunities for developing new photoelectronic devices and biological active materials.?5?Selective synthesis of unsaturated conjugated heterocycles from alkynes using a proton acid/N-chlorophtalimide system.Described here is a strategy to achieve two different regioselectivities from alkyne,isothiocyanate and H₂O using a‘proton acid/N-chlorophtalimide?NCPI?'system.When Fe₂?SO₄?_3·x H₂O was used as catalyst,trifluoromethane sulfonic acid as additive and fluorobenzene as solvent,1-oxathiol-2-imine derivatives were obtained,while thiazole-2-one derivatives were formed when formic acid or hydrochloric acid was used as additive,nitromethane and hexafluoroisopropanol were used as co-solvent.Mechanistic studies support that transformation includes a combination of H₂O and isothiocyanate,free radical formation,carbonation and intramolecular cyclization to give the products.