Study On The Cycloaddition Reaction Of Alkenyl Sulfide And Pyrazolinone

Nitrogen heterocyclic compounds as the core structure framework are widely present in a variety of natural products and drug molecules with significant biological activity.Therefore,it is particularly important to develop a mild and green synthetic method to efficiently construct such compounds.Based on the properties of alkenyl sulfonium salts,in this article,we developed a base-promoted cyclization tandem cyclization reaction,and successfully realized the efficient construction of two types of nitrogen-containing heterocycles.1)The [2+1] tandem cyclization reaction of alkenylsulfonium salt and pyrazolin-5-one generated in situ from 2-bromoethylsulfonium salt was developed.And a variety of functionalized spirocyclopropyl fused pyrazolin-5-one derivatives are obtained in good to excellent yields.The synthesis method has the advantages of mild reaction conditions,good functional group compatibility,cheap and readily available raw materials,and simple operation.In this reaction,2-bromoethyl sulfonium salt is used as the precursor of vinyl sulfonium salt,followed by Michael addition reaction with pyrazolone to generate active sulfur ylide in situ.After proton transfer,intramolecular nucleophilic substitution The spirocyclopropyl fused pyrazolin-5-one derivatives is obtained.2)The [4+2] tandem cyclization reaction of vinylsulfonium salt and ?-ester hydrazone under the promotion of alkali was explored,and a preliminary study was made on the universality of the substrate.The tetrahydropyridazine derivative was obtained in a moderate yield.In this reaction,the vinyl sulfonium salt acts as the Michael acceptor,followed by the Michael addition reaction with the 1,4-binuclear nucleophile ?-ester hydrazone to generate active sulfur ylides in situ.After proton transfer,the intramolecular nucleophilic Substitution gives tetrahydropyridazine derivatives.