Study On The Direct Ortho-acylation Of Azoxybenzenes Viapalladium-catalyzed Regioselective C-H Bond Activation

In this thesis, the direct ortho-acylation of azoxybenzenes via palladium-catalyzed regioselective C-H bond activation was studied. The main results obtained are shown as belows:Azoxyarene and its derivatives are widely applied in the fields of polymerization inhibitors, chemical stabilizers, DNA cleavers, organic synthesis, dyes and key materials in the sphere of electronic displays and therapeutic medicines based on their liquid crystalline properties. As a result of their importance, a number of methodologies have been established to build such a structural skeleton. Transition metal catalyzed direct C-H bond functionalization is hot topic recently due to its atomic economic reaction. However, on account of the two kinds of C-H bonds at ortho-azoxybenzenes of the nitrogen atom, development of a simple, highly efficient and atomic economic method to utilization of azoxy compounds in group-directed C-H activation and functionalizations has been challenging.Hence, a highly efficient and convenient palladium catalyzed the ortho-acylation of azoxybenzenes has been developed(Scheme 1). Azoxybenzenes were used as the specific substrates with a “green” oxidant of TBHP in the presence of a catalytic amount(5 mol %) of Pd(OAc)2, and easily available aldehydes were employed as a cheap and ideal aroyl source. This method provides a practical and direct pathway to synthesize 2-acylated azoxybenzenes with up to 89 % yields in chemo- and regio-selective manners via Palladium-catalyzed C-H bond activation. In this procedure, various substituents on both coupling partners are tolerated well. The structure of the products were identified by NMR spectra, HRMS and the X-ray single crystal structure analysis. The mechanism of this transformation was based on the controlled experiment results and literatures(Scheme 2). Scheme 1 Scheme 2...