Study On Arylation And Alkenylation Of Heterocycle C-H Bonds Catalyzed By CuO Nanoparticles

Heterocycles are one of the most important motifs of organicchemistry and are distributed in various natural products, which havegreat value of application in pharmaceuticals, dyes, pesticides andorganic materials. Therefore, searching simple and efficient methods forthe synthesis of heterocycles and their derivatives have receivedconsiderable attention. In recent years, the area of heterocycle synthesishas especially benefited from copper facilitated transformation. Amongthem, the simplest approach is the copper-catalyzed direct C-Hfunctionalization.This thesis contains three parts, detailed as follow:The first part covered recent progress in the synthesis ofheterocycles and their derivatives. On one hand, heterocycles and theirderivatives are obtained by cyclization; on the other hand, they areobtained by the C-H functionalization of heterocycles.The second part is about the study on the reactions of heterocycleC-H bonds and aryl bromides catalyzed by CuO nanoparticles.On the basis of previous work of our lab, we developed nanoparticleCuO-catalyzed method for the synthesis of heterocycles’ derivatives byarylation of the C-H bond of heterocycles and cheaper aryl bromides.CuO nanoparticle have been synthesized through a convenientalcohothermal approach using Cu(OAc)2as starting materials, and werecharacterized by XRD、SEM、TEM analysis. Then, we chose benzoxazoleand bromobenzene as substrate and focused on searching for catalyticalproperties and suitable reaction conditions in the arylation of heterocycleC-H bonds. The result showed that CuO nanoparticle could efficientlycatalyze the reaction, using diglyme as solvent and K2CO3as base, in thepresence of PPh3under reflux in moderate to good yields. Under theoptimized reaction conditions, benzoxazole, benzothiazole and 1-methylbenzimidazole could react with aryl bromides and afforded thedesired products in good yields. The arylation of heterocycle shows thatthe presence of electron-withdrawing groups on aryl bromides leads tohigher yields than those with electron-donating groups.3-bromopyridinecould also reactive with various heterocycle in excellent yields, whichenrichs methods for the synthesis of biheteroaryls. This reaction systemcan use mild inorganic base and raw materials easy to get. The catalysts,with the stable and available property, can be synthesized by a verysimple method and recycled in order to reduce the pollution of theenvironment.The third part is to study on the reactions of heterocycle C-H bondsand alkenyl bromides catalyzed by CuO nanoparticle.We researched the reaction of heterocycle C-H bonds and alkenylbromides through this catalyzed system and succeeded to get seriescorresponding products. Both electron-rich and electron-deficientβ-bromostyrene reacted with benzimidazole in moderate to good yields.In general, the presence of electron-withdrawing groups onβ-bromostyrene leads to higher yields than those with electron-donatinggroups. In addition, we found [2+2] cyclization products directsynthesized via coupling of vinyl heterocycles themselves. Furtheroptimization of conditions and the detailed mechanism are currentlyunderway.