The Studies Of Palladium-Catalyzed C-H Bond Activation Assisted By Directing Groups

For its ability of coordinating to nitrogen and oxygen, palladium have been becoming the most efficient catalyst for the directing C-H activation. Nowadays, O-containing and N-containing directing groups assisted C-H activation reaction catalyzed by palladium have been widely studied. In despite of this advance, to search the easily transformable, easily removable or newly tape of directing groups still the hot topic in directed C-H activation reaction currently.This dissertation mainly focused on the studies of palladium catalyzed C-H bond activation assisted by the easily removable and transformable directing groups, which include:1. Pd(OAc)2-catalyzed C-H alkenylatin and arylation of arenes assisted by removable2-pyridylsulfinyl GroupNowadays, palladium-catalyzed chelation-directed C-H activation has been widely researched. However, in some cases the practicality might be restricted when the directing groups cannot easily be removed from the products. Therefore, significant effort has been directed toward the discovery of efficient and removable directing groups currently. We studied Pd(OAc)2-catalyzed C-H alkenylation and arylation of arenes assisted by removable2-pyridylsulfinyl group. It was found that a variety of alkenes selectively undergo the direct alkenylation in moderate to good yields. More importantly, this transformation could also be applied in arylation through dual C-H activation with simple arenes. Finally, as we expected, the2-pyridylsulfinyl group could be removed easily after the C-H bond functionalization under reductive conditions or afford diverse reduction products. 2. Pd(OAc)2-catalyzed C-H alkenylatin of arenes using thioether as directing groupsThioether is an important structural motif in a wide range of molecules with numerous and important applications. It exists in drugs and natural product. It also has been widely used as coordination groups with various metals in many useful complexes. We studied Pd(OAc)2-catalyzed C-H alkenylation of arenes using thioether as directing groups. It was found that the alkenylation could undergo smoothly in moderate to good yields when using thioether as the directing group. It could obtain good regioselective and stereoselective. In most cases, the (E)-isomers were isolated as the major products; and the double alkenylated product can also be obtained with some special substrates. Finally, the alkenylated thioethers can be easily removed and transformed into a variety of useful groups.3. Pd(OAc)2-catalyzed Regioselective y-Mono-and Diarylation of Acrylamide Derivatives with Aryl HalidesFor the past several years, some examples about sp3C-H activation have been reported. But C(sp3)-H bond activation remains a challenging problem because of its high bond dissociation energy and lack of π-participation. As we all know, allylic hydrogen is more active then the normal alkyl hydrogen. We studies y-sp3C-H activaion of Acrylamide Derivatives. It is found that the γ-position C-H bond arylation of the acrylamides can be smoothly achieved and the subsequent double bond shift leads to the formation of β,γ-unsaturated amide products. The α-and/or β-regioisomeric arylation products are not detected in this transformation. Meanwhile, we have studied the reaction mechanism carefully, it will be helpful for understanding this kind of chemistry.