Palladium/Norbornene Catalyzed Ortho C-H Activation Reactions Of Iodobenzenes

In recent decades, transition-metal catalyzed cross-coupling reactions have been widely investigated because of their practical applicability and effectiveness in the construction of carbon-carbon bonds and carbon-hetero atomic bonds. Palladium-catalyzed/norbornene-mediated one-pot C-H activation and C-I activation is an important reaction, which offers an important atom-economic method to construct carbon-carbon and carbon-heteroatom bonds.In this thesis, palladium/norbornene catalyzed C-H activation and further cross-coupling reactions of iodobenzenes were investigated. This thesis consists of three parts as follows:1. Palladium-catalyzed one-pot consecutive amination and Sonogashira coupling for selective synthesis of 2-alkynylanilinesPd(OAc)2/norbornene catalyzed ortho C(sp2)-H activation and Sonogashira coupling reaction of iodobenzenes were studied.2-Iodotuluene reacted with O-benzoyl hydroxylamine and 2-methyl-4-phenylbut-3-yn-2-ol catalyzed by Pd(OAc)2/PPh3 and mediated by norbornene in 1,4-dioxane at 100℃, giving ortho alkynyl anilines in one-pot. The results show that substituted iodobenzenes, alkynols and cyclic or noncyclic amination reagents are all suitable for this reaction. The electron-donating groups on iodobenzenes improved the yields of the products, and the steric-hindrance effect had little effect on the reaction. Both electron-rich and electron-dificient alkynyl reagents worked smoothly under the standard reaction conditions. In addition, the aliphatic alkynyl reagents also afforded the desired products.2. Palladium-catalyzed sequential acylation/cyanation of aryl iodides: a regiospecific synthesis of 2-cyano diaryl ketonesPdCl28/norbornene catalyzed ortho C-H activation and transmetalation reaction of iodobenzenes were studied.2-Iodotoluene reacted with benzoyl choloride and CuCN catalyzed by PdCl2/TFP and mediated by norbornene in 1,4-dioxane at 100℃, giving 2-cyano diarylketones in one-pot. Further mechanistic studies indicated that anhydride formed in situ was the reactive intermediate of the reaction. When iodobenzenes with strong electron-withdrawing groups were used as the substrates, the homo-coupling products of two molecules of iodobenzenes and CuCN were afforded.3. Palladium-catalyzed/norbornene-mediated sequential acylation/heteroarylation of aryl iodidesPdCl2/norbornene catalyzed ortho C-H activation and metaltranslation reaction of iodobenzenes were studied, introducing benzoyl and heteroaryl group on iodobenzene.2-Iodotoluene reacted with benzoic anhydride and benzoxazole catalyzed by PdCl2/TFP and mediated by norbornene in CH3CN at 100℃, giving ortho-heteroarylated diarylketones in one-pot. When benzoic anhydrides containing electron-donating groups were employed in the reaction, the products could be obtained in high yields. For benzoic anhydrides bearing electron-withdrawing substituents, the yields of the corresponding products were much lower. The steric hindrance effect played a critical role in the reaction.