Copper(?)-Catalyzed Oxyamination Of ?,?-Unsaturated Hydrazones:Synthesis Of Dihydropyrazoles

Purpose:Dihydropyrazoles are widely used in the fields such as pesticide,material,medicine and fluorescent probe.Recently,radical-mediated intramoleculor cyclizations of ?,?-unsaturated hydrazones are regarded as an ideal approach to form functionalized dihydropyrazoles.The oxyamination of alkenes represents a valuable strategy for the synthesis of 1,2-amino alcohol derivatives.However,most of the oxyaminations of alkenes are needed expensive metals and stoichiometric amounts of oxidants and corrosive acids,which are not in accordance with the requirements of green chemistry.Thus,we have exploited copper catalyzed oxyamination of ?,?-unsaturated hydrazones to synthesize dihydropyrazoles.Methods:An efficient copper(I)-catalyzed oxyamination of ?,?-unsaturated hydrazones with molecular oxygen in a one-pot process has been developed.At the same time,we carried out related verification experiments and proposed two possible reaction mechanisms.Results:The methodology provides effective access to dihydropyrazole derivatives in 20%-76% yield.In the mechanism study,it is found that the catalytic process of this reaction involves multiple oxidation forms,and the target product is obtained by two redox routes.Conclusion:Mechanistic studies have been performed and are suggestive of an aerobic manifold via single electron transfer.