Tandem Dicyclization Of Substituted Aryl Isothiocyanates Catalyzed By Cheap Copper

Tandem dicyclization can easily and efficiently synthesize complex compounds by building multiple chemical bonds at one time,so it has a wide range of applications in the synthesis of medicine,pesticides and natural products.In this paper,we discuss the tandem dicyclic reaction of substituted aryl isothiocyanates catalyzed by cheap copper,which is divided into the following two aspects.In the first part,a quick synthesis of 5H-benzoimidazole [5,1-b][1,3] thiazide using cheap metal copper(I)catalyzed by tandem dicyclization of o-acetyl-aryl isothiocyanate and(E)-2-(benzylamino)acetate.Under the catalysis of copper chloride(I)and base,the C-H bond of(E)-2-(Benzylidene amino)acetate will be activated to form the intermediate,which will also undergo [3+2] cycloaddition reaction with the N-C bond in isothiocyanate,and the isomerized intermediate will undergo intramolecular nucleophilic cyclization to obtain the target product.The method is simple,economical,environmental friendly and efficient.The same one-pot method is used to synthesize two rings simultaneously.In the second part,a cheap metal copper catalyzed the synthesis of 5Hbenzotetrazole and thiazide compounds by tandem bicyclization of o-enyl aryl isothiocyanate and sodium azide.The [3+2] cycloaddition reaction occurs between the azide anion and the N-C bond of isothiocyanate in sodium azide,and then the intermediate is obtained.Then the isomerized intermediate is catalyzed by the intramolecular Michael addition reaction,and finally the target product is obtained.The method provides an efficient synthesis route for thiazide derivatives by using low toxicity and cheap copper salt as catalyst.