Electrochemically Promoted Cross-coupling Reactions Of Sulfinates And Phosphites With Phenol And Mercaptan

Organic electrochemical synthesis is an interdisciplinary subject which combines traditional organic synthesis with modern electrochemical technology.Compared with using traditional redox agents,electrochemistry uses anode and cathode as oxidant and reductant so as to avoid the need for a large amount of oxidants and reductants in reactions,it also avoids the use of alkali to neutralize the H⁺ions which are generated during traditional reaction processes.All H⁺ions can be directly reduced on the cathode and released in the form of hydrogen.The process is green and environmentally friendly,and even produces clean energy gas hydrogen.The electrochemical reaction is generally environment-friendly,the reaction conditions are mild,and the post-treatment is simple.In recent years,more and more researchers pay attention to the electrochemical synthesis methods,which has become a powerful supplement to the traditional organic synthesis method.Its development speed is amazing,so it is more meaningful to do electrochemical reaction research.Organic sulfide and organic phosphide are widely distributed in nature,which are of great significance to life activities.Organic sulfide and organic phosphide have very wide applications in life science,pharmaceutical chemistry,food chemistry and material science.Among them,thiosulfonate（R₁-SO₂-S-R₂）,（R₁-SO₂-O-R₂）has a variety of biological activities,such as antimicrobial,antifungal,insecticidal and antiviral drugs.Organophosphate is widely used in flame retardant,pesticide,pharmaceutical chemistry,material science,semiconductor and other fields.In addition,organophosphorus has been used as effective chiral phosphorus ligands in many asymmetric organometallic reactions.The traditional synthesis methods of R₁-SO₂-S-R₂,R₁-SO₂-O-R₂ and（RO）₂P（O）-OR₁ are generally obtained by the reaction of sulfonyl chloride or sulfinyl chloride or phosphoryl chloride with thiophenols,phenols or alcohols.during the reaction processes,there are many toxic and odorous raw materials,some oxidants and reducing agents,and even some organic bases and inorganic bases are involved.In this paper,based on the previous work,we try to convert these reactions into electrochemical reactions.The main work of this paper includes the following three parts.In the first part,we developed an electrochemical oxidation cross coupling reaction to realize the cross-coupling of sodium benzenesulfite and thiophene with different substituents in undevided cell.Sulfonyl thioester（R₁-SO₂-S-R₂）was obtained in high yield and SO₂-S bond was constructed.Compared with the traditional method,this method has the advantages of mild conditions,green ring,avoiding the use of toxic reagents,and no need to use additional oxidants.In addition,we also do control experiments and cyclic voltammetry experiments to explore the reaction mechanism.In the second part,on the basis of the first part,we explored the extension of the reaction,studied the cross-coupling reaction of sodium benzenesulfite with different electron withdrawing and electron donating groups and different structures of phenols,and achieved the direct electrochemical synthesis of sulfonate（R₁-SO₂-O-R₂）without transition metal catalyst and oxidant,SO₂-O bond was constructed.A large number of sulfonate compounds for transition metal coupling can be synthesized by this method.This method has wide amplification performance and practicability.In the third part,we explored the construction method of P（O）-O bond by electrochemical oxidative coupling reaction,realized the dehydrogenation cross-coupling between aromatic phenolic compounds and diethyl phosphite,and obtained aryl phosphate compounds in high yields.This method has guiding significance for the construction of P（O）-O bond in biological phosphorus molecules in the future.Compared with the traditional synthesis method,this electrochemical method avoids the use of toxic chlorination reagents and the reactions proceed under mild reaction conditions,it is environmentally friendly and atomic economy.In addition,we explored the reaction mechanism,measured the cyclic voltammetry,and gave a plausible reaction mechanism.In a word,based on the previous research work,we explored three electrochemical oxidation cross-coupling reactions in detail,successfully constructed SO₂-S,SO₂-O,P（O）-O bonds,and obtained sulfonyl thioester,sulfonyl ester and phosphate with three different structures.All the reaction conditions are mild,green and high yield.Through the use of electrochemical method two is not the traditional method,these reactions avoid the traditional reaction need to add a lot of oxidants or reducing agents,and even need the existence of organic and inorganic bases,reduce the amount of waste generated by the reaction,which also has a good reference significance for the follow-up research.