Studies Of Pd-Catalyzed C-H Bond Arylation Oxidantion Cyclization Of Enamines

Oxazole represents an important structural unit that is prevalently found in natural products,pharmaceutical agents,and functional materials.In particular,2,4,5-trisubstituted oxazoles exhibit special optical and biological activities.Accordingly,more general and versatile synthetic methodologies for this class of compounds are highly desirable for both industry and academia.Traditionally,2,4,5-trisubstituted oxazoles are synthesized by condensation from the acyclic precursors,which often suffer from harsh reaction conditions and limited substrates.Recently,transition-metal-catalyzed C-H bond activation has been developed to overcome these drawbacks.Because of high efficiency and atom economy,transition-metal-catalyzed C-H bond activation using directing group has attracted many scholars to conduct in-depth research and developed into a powerful tool for building useful heterocycles.In this thesis,we report a facile protocol for the synthesis of versatile 2,4,5-trisubstituted oxazoles by amide group directed palladium catalyzed C-H functionalization from readily available N-acyl enamides and iodobenzene under mild reaction conditions.The transformation is supposed to undergo the amide-directed arylation of alkenyl C-H bond of enamides by palladium catalysis followed by the oxidative cyclization to give the desired oxazoles.The reaction displayed exceptional compatibility with a wide range of functional groups to give the diverse multi-substituted oxazoles in good yields,which provides an efficient way to synthesize 2,4,5-trisubstituted oxazoles.In addition,we conducted control experiments to obtain insight into the mechanism of the reaction process,and a plausible reaction mechanism was proposed.