Studies On Palladium(0) Catalyzed Heck Raction And Suzuki Reaction As Well As Palladium(Ⅱ) Catalyzed Wacker Oxidative Cyclization

Palladium catalysts and reagents play an important role in organic synthesis, particularly in carbon-carbon coupling reactions. No other transition metals can offer such versatile methods as Pd. Besides, palladium catalysts have widely used in industry process, which have displayed its promising prospects.In this thesis, three parts are included. The first part is about the recent development of palladium chemistry and its application; the second part focus on the palladium catalyst cross coupling reaction; the last section describe a new type of Wacker-type reaction, bywhich three types of heterocycles were obtained.1. Cross coupling reactions catalyzed by palladiumHigh temperature and organic solvent are always required in Heck reaction, which is also highly sensitive to air. We developed an aqueous Heck reaction promoted by in-suit formed nano-particles palladium, which were characterized by TEM and XRD analyses, in the presence of ultrasonic irradiation. Furthermore, the Heck reaction under such mild and environmentally conditions offers excellent regioselectivity of C-I bonds.In order to reduce the cost of high expensive palladium catalyst, we further investigate the heterogeneous palladium catalyst. The natural widespread diatomite was chose as a template to support palladium. Also, XRD and XPS analyst confirmed the result. The catalytic activity of this novel heterogeneous was proven by Heck reaction and Suzuki reaction.2. Palladium(II) catalyzed Wacker-type oxidative cyclizationPalladium-catalyzed Wacker-type oxidative cyclization is one of the most important processes in the synthesis of heterocycles. On the basic of literatures, the products of allylation reaction (homoallylic alcohol) were chose as the substrate and three types of heterocycles were obtained by this method.1) 2-methyl chromenones were obtained by Wacker oxidative cyclization startingfrom the allylation of salicylaldehyde. We also studied the mechanism of this novelreaction, which indicate that an unusual 1,5-hydride alkyl to palladium migration wasinvolved. Deterium labeling and chirality transfer experiment supported thismigration.In general,β-hydride elimination process is popular in Wacker-type reaction, which can not explain our observations. On the other hand, the 1,5-hydride alkyl to palladium migration process not only fit very well with the results but also expand the mechanism in palladium chemistry.2) 2-methy quinolines were obtained via aza-Wacker cyclization. The substrates for this transformation are the allylation products of 2-amino-benzadehyde. The 1,5-hydride alkyl to palladium migration was not observed but a dehydration process was involved.3) From natural amino acids, pyrroles were obtained after five steps, in which the key step is an aza-Wacker cyclization. The structures of pyrroles could be controlled by different amino acids.