Synthesis Of Benzothiazole And Phenothiazine Derivatives From Aromatic Amine And Elemental Sulfur

Nitrogen and sulfur-containing heterocyclic compounds like benzothiazoles,phenothiazines et al.are extremely important organic compounds.2-Arylbenzothiazoles play an important role in potential drugs such as anti-tumor agents,anti-tuberculosis drugs,anti-parasitic drugs and calcium channel antagonists.In addition,some 2-arylbenzothiazoles are widely used in other functional molecules such as industrial dyes,organic light emitting materials,and agrochemicals.Phenothiazine derivatives are commonly found in psychiatric drugs and antihistamines,and to a certain extent,they can treat some mental diseases such as depression,parkinson’s disease and anxiety.Phenothiazines are also widely used in industry.They are mainly used as polymerization inhibitors,antioxidants,conductive materials and dyes.Therefore,the preparation of benzothiazole and phenothiazine compounds has always been one of the important areas in the synthesis of heterocycles,and a large number of synthesis methods have been reported.Due to its important biological activity,it is still necessary to develop new and highly efficient synthetic pathways for the rapid construction of complex and diverse benzothiazole and phenothiazine derivatives.In this paper,we studied the synthesis methods of 2-arylbenzothiazoles and phenothiazines by using elemental sulfur and aromatic amines as the sulfur and nitrogen sources,respectively.The main contents are as follows:1.Three-component "one-pot" synthesis of 2-arylbenzothiazoles was carried out using aromatic amines,elemental sulfur and benzaldehyde as the raw materials.The reaction involved oxidative cyclization and C-H bond functionalization process.In this reaction,in the absence of transition metal catalysis,NH4I or KI served as catalysis and DMSO or oxygen served as oxidant and readily available elemental sulfur,aromatic amines and benzaldehyde were used as the raw materials.The reaction has good substrate applicability and functional group stability.Gram-scale reactions also yield better benefits,providing a convenient new route for 2-arylbenzothiazoles.2.Three-component "one-pot" synthesis of phenothiazine using arylamine,elemental sulfur and cyclohexanone as the raw materials was studied.In this method,the cheap and easily available CuI or I2 were used as catalyst to synthsize phenothiazines through a condensation/dehydrogenation/aromatization seqeunse.Cyclohexanone and aromatic amine respectively serve as the two aryl sources of phenothiazine.Compared with the construction of phenothiazine derivatives using organic sulfur sources,this method does not require the use of unpleasant organosulfur reagents,and the reaction is more direct and does not require multifunctional clumps.The raw materials are simple and the operation is easy.