Synthesis Of 2-acylbenzothiazoles And 1,3,4-oxadiazole Derivatives Via Tandem Cyclization Reaction

N-heterocyclic compounds are an important class of heterocyclic compounds,which are widely used in agriculture,medicinal chemistry,and luminescent materials.Benzothiazoles and 1,3,4-oxadiazoles exhibit a wide range of pharmaceutical and biological activities.Therefore,it is of great significance to explore efficient,economic and environmentally friendly methods for the synthesis of benzothiazoles and 1,3,4oxadiazoles.In this dissertation,an efficient one-pot method to access 2-acylbenzothiazoles via AlCl3-mediated cyclization reaction and I2-promoted sequential oxidation reaction of 2-aminobenzenethiols with arylacetonitriles was developed.Moreover,I2-mediated oxidative cyclization reaction for the synthesis of 1,3,4-oxadiazoles from 4phenylsemicarbazides and arylmethyl ketones was studied.The above methods utilize readily accessible compounds as starting materials and I2 as green oxidant for the synthesis of two type five-membered N-heterocyclic compounds.The main research contents are as follows:(1)Synthesis of 2-acylbenzothiazole and its derivatives.An efficient one-pot method to access 2-acylbenzothiazoles via AlCl3-mediated cyclization reaction and I2promoted sequential oxidation reaction of 2-aminobenzenethiols with arylacetonitriles was developed.By investigating various factors,the optimized conditions were established.Subsequently,the suitability of a series of substituted acetonitriles and 2aminobenzenethiols was investigated,and the corresponding products were obtained in moderate to high yields.Besides,this reaction was conveniently conducted on a gram scale and the yield is still up to 68%.Finally,a series of control experiments and free radical trapping experiments were carried out and these results indicated the reaction might involve a free radical process.The possible reaction mechanism was proposed.(2)Synthesis of 1,3,4-oxadiazole and its derivatives.A novel approach to access 5-amino-2-benzoyl-1,3,4-oxadiazoles via I2/DMSO promoted oxidative cyclization of 4-phenylsemicarbazide and(het)aryl methyl ketones was developed.The reaction is simple,environmentally friendly,mild reaction conditions.Finally,on the basis of literature reported,a possible reaction mechanism was speculated.