Selective Free Radical Oxidative Cracking Of Chalcone Epoxides And Efficient Synthesis Of Pyrazole Derivatives

Epoxides are widely used as substrates in organic synthesis because of their high reactivity and easy availability.However,the selective cracking and transformation of?,?-epoxidone compounds remains one of the most challenging tasks for chemists.In recent years,selective cracking of ?,?-epoxidone compounds in the absence of transition metals has attracted more and more attention due to its obvious advantages in terms of cost and environmental compatibility.In addition,due to the special properties of a large number of pyrazole derivatives in pesticide,medicine and materials,researchers are more interested in pyrazole compounds,especially pyrazole derivatives with chalcone as the framework.Firstly,a series of epoxidized chalcones and spiroxycidones were synthesized in order to study the selective cracking and transformation of ?,?-epoxidones.Then,the selective oxidative cleavage of the epoxy carbon-carbon bond of epoxidized chalcone was achieved in the presence or absence of solvent by using tertbutanol peroxide(TBHP)as the free radical initiator and oxidant.The corresponding aldehydes and acids were obtained in 48.3%-95.2%and 63.2%-98.6%yields in the presence of diethylene glycol dimethyl ether and the corresponding two acids can be obtained with a yield of up to 99%in the absence of solvent.The effects of solvent,temperature,feed ratio,reaction time and other factors on the reaction were investigated respectively.The optimized conditions are:substrate:TBHP=1:12(molar ratio),solvent diethylene glycol dimethyl ether,temperature 140?,the reaction time is 95 minFinally,a series of pyrazole derivatives were designed and synthesized using epoxidized chalcones as substrates.And the solvent temperature,feed ratio,reaction time and other reaction conditions were optimized,The optimal reaction conditions were as follows:solvent toluene,temperature 100?,molar ratio 1:1.2(chalcone epoxide:benzene sulfonyl hydrazide),time 3 h.Twenty-five unreported pyrazole derivatives were obtained with yields of 62-82%.In the future,we will study the anti?-Syn aggregation activity of these pyrazole derivatives.