The Reaction Study Of Lewis Acid Catalyzed Benzenesulfonyl Hydrazone With Ethyl 1,1-Dicarbonyl-2-Aryl-Cyclopropane

The effective utilization of ring strain has considerable advantage for the establishment of complex molecules.The cyclopropane has been widely used as building blocks in organic synthesis.It can undergo cycloaddition reactions with a variety of pro-dipolar body in the presence of Lewis acid as a catalyst due to the large ring strain,and the ring-opening reaction with electrophilic or nucleophilic reagent can also occur.However,among the pro-dipolar bodies,the reports for C=N-N skeleton of hydrazone was utilized remain rare,which greatly attracted our attention.This paper reported that cycloaddition and ring-opening of cyclopropane with hydrazone catalyzed by Lewis acid simultaneously occurred in the same system,providing three different types of target products with high yields.The reaction was carried out through selecting benzenesulfonyl hydrazone and1,1-diesters-2-aryl-cyclopropane as standard substrates.By examining the catalyst,solvent,temperature and the material ratio,the optimal conditions were obtained as followed:double catalysts Sc?OTf?₃?5 mol%?and SnCl₄?20mol%?,1,1-diesters-2-aryl-cyclopropane?0.35 mmol?,benzenesulfonyl hydrazone?0.1 mmol?,20 mg of 4?-MS as an additive in toluene?1 mL?at 40^oC.At last,three kinds of the target products were offered.Under the optimal conditions,scopes of the aryl cyclopropane and arylsulfonyl hydrazone were respectively explored and more than 30 desired products were obtained with excellent yields.Finally,the products were determined by using ¹H NMR,¹³C NMR and HRMS.During the course of exploring this subject,we found that the reaction was not carried out in accordance with the initial conception of[3+3]cycloaddition of cyclopropane with benzenesulfonyl hydrazone.It accessed to more complex ring-expansion reaction,meanwhile the methyl benzenesulfonyl of the hydrazone also combined with cyclopropane providing sulfur ring-opening product.The reaction have significant medicinal research value because it constructed not only nitro-heterocyclic product containing C=N-N three-atom,but also ring-opening product including carbon-sulfur bond.