Study On The Tandem Reaction Initiated By Electrocatalytic Thiocyanate

In recent years,organic electrochemistry has received more and more attention because of its use of electrons as redox reagents,which provides a powerful green method for building new chemical bonds.Electrochemical anodic oxidation can realize the direct or indirect activation of the substrate,and the cathode reduction can also realize the direct or indirect activation of the substrate,thereby generating the corresponding target product.Electrons take the place of redox reagents,which avoids the formation of environmentally harmful wastes and greatly improves the atomic efficiency of the reaction.Among them,the tandem cyclization reaction under electrochemistry is the greenest and most effective method to construct polycyclic compounds,which can avoid the redox agents,catalysts or metal reagents used in the traditional tandem cyclization reactions,which aroused research interests of our group.Thiocyanate is the most direct and cheap reagent to introduce thiocyanate group.At the same time,the obtained thiocyanate is an important organic synthesis intermediate,thiocyanate can not only be converted into various sulfur-containing compounds such as thioether,thiocarbamate,phosphorothioate,etc.,but also various sulfur-containing heterocyclic compounds can be obtained.In addition,this type of compound has a variety of biological activities,and has important application value and broad application prospects in many fields such as drugs and materials.Moreover,thiocyanate can also be used as a reagent for introducing isothiocyanate group.The obtained isothiocyanate is an important precursor for the synthesis of a variety of sulfur-containing heterocyclic compounds.However examples of isothiocyanate obtained through this idea were rarely reported,this also aroused the research interest of our group.This thesis uses readily available ammonium thiocyanate and N-allyl thioamide as starting materials.Under the promotion of electricity,tandem cyclization can obtain thiazoline containing thiocyano group.First,the optimal reaction conditions were determined by screening conditions:the ratio of ammonium thiocyanate to N-allyl thioamide was 2:1,the solvent was acetonitrile,and the reaction was performed at a constant voltage of 2 V for 5 h at room temperature.The reaction does not require metal reagent,oxidant and additional electrolyte.The synthesized new compounds have been characterized by ¹H NMR,¹³C NMR,HRMS,and X-single crystal diffraction analysis.Subsequently,gram scale experiment and follow-up transformations were performed,which exhibited the application value of the reaction.Finally,through a series of control experiments and cyclic voltammetry experiments,we proposed a possible reaction mechanism.At the same time,this paper uses ammonium thiocyanate and thioamide with cyclic olefin as substrates.Under the promotion of electricity,tandem cyclization can obtain1,3-thiazine compounds containing isothiocyanate groups.The reaction conditions are mild,and the reaction can be carried out at room temperature without the need of metal reagents,oxidants and additional electrolytes.The realization of this reaction provides a green and efficient method for the introduction of isothiocyanato groups and the construction of thiazides.