Ortho-C-H Bond Cyanation And Alkylation Of 2-arylbenzothiazole Derivatives

During the last decade,great novel organic synthesis reactions,reagents and catalytic methods have been emerging,which provides a powerful weapon for organic synthesis chemists.Therefore,various complex conversions have been sucessfully achieved under mild reaction conditions with higher chemical selectivity,regioselectivity and stereoselectivity.Organic chemistry is the science of the study of carbon containing compounds and C-H bond almost exist in every step of organic chemistry.Due to the universality of C-H bond itself in the structure of organic compounds,the direct conversion of the C-H bond has been the focus of organic chemists.Although C-H bond activation seems to be difficult,it has important theoretical and application value.From the point of view of basic scientific research,the direct activation of C-H bond will help to open a new chapter in the study of organic chemistry.Benzothiazole skeleton was found in many natural products and significant pharmaceuticals with remarkable biological activities.Among them,2-arylbenzothiazole derivatives have attracted great interest in synthetic chemists due to their excellent pharmacological effects,such as antitumor,antibacterial and neuroprotective activity.In addition,2-arylbenzothiazole derivatives can be used as fluorescence probe and organic light emitting diode(OLED)materials.Therefore,it is highly desirable to develop efficient strategies for access to functionalized novel2-arylbenzothiazoles.Recently,we and other group described several transition metal-catalyzed ortho-C-H bond functionalizations of 2-arylbenzothiazoles,such as arylation,alkylation,acylation,acetoxylation,halogenations,amination,olefination,hydroxylation and nitration.In the first part of this thesis,we introduce the advances of transition metal catalyzed C-H bond cyanation and alkylation reaction.In the second chapter,a mild and efficient substrate-assisted C-H bond cyanation of2-arylbenzothiazoles has been developed using Cu CN as cyano-group source.The use of I2/Ph I(OAc)2 oxidant allows for high efficient and regioselective sequential iodination/cyanation of 2-arylbenzothiazoles.In chapter three,we have successfully developed the rhodium-catalyzed direct ortho-C–H bond alkylation of2-arylbenzothiazoles and 2-arylthiazoles by using potassium alkyltrifluoroborates as the alkyl group source.