Investigation Of Methodology Based On Ynamides, And Synthetic Studies Towards Precursor Of Cephalotaxine

The main content of the thesis include review on the development of ynamide chemistry, methodology research based on ynamide as well as synthetic studies towards Cephalotaxine precursors. The dissertation consisted of mainly three parts as follows: Chapter 1: Studies on synthesis of biaryls via palladium-catalyzed cross-coupling reactions of diazo compounds.Ynamides, which can be considered as subgroup of alkynes, have been vastly utilized in developing synthetic methods and have a unique structure with a nitrogen directly attached to the acetylenic bond. The polarization of the nitrogen lone pairs to the triple bond as well as the alteration of activity caused by electron-withdrawing-group leads to a special performance at regioselectivity and stereoselectivity. In addition to a few important documents early, the thesis has focused on the rapid development of ynamide since 2000. It summarizes the history ynamides’ emergence, evolution of preparation methods, various types of reactions involved as well as application in natural product total synthesis. Chapter 2: Methodology researth based on ynamides.In consideration of versatile chemical properties of ynamides, methodology researches were carried out though three different reactions. First the Au catalyzed interactions of ynamides towards nuclephophiles were investigated. The generation of α-oxo gold carbenes via gold-catalyzed alkyne oxidation is representive, and we use a variety of different gold catalyst system and external oxidant, try to capture the appropriate nucleophile in situ generated Jinka Bin to achieve difunctionalization. Without external oxidant, gold catalyzed activation of ynamide favor nucleophile attack as well.A new mehods for the I2 induced preparation of α-keto amide under and preparation of diiodide according to addition of I2 have been established. The methods avoid the traditional preparation of amide carbonyl common metal catalyst, strong oxidizing agents and intense reaction conditions in the traditionalpreparation, and the addition reaction of elemental halogen ynamide very rare. Using the samesubstrates, the reaction products depend on the solvent.A new method for the prepatation of Stereoselective Synthesis of(2Z)?2,4-Dienamides via NBS- Mediated Allyloxyl Addition- Claisen Rearrangement- Dehydrobromination Cascade Reaction. Different from the common metal catalytic system, NBS was use for the activation of ynamideChapter 3: Synthetic studies towards Cephalotaxine.Cephalotaxine alkaloids belong to a family structurally uninque plant natural products. Cephalotaxinev possesses a unique benzazepine-bearing pentacylic ring skeleton, which has stimulated numerous synthetic studies and represents a classic target molecule in natural product synthesis. The synthestic studies on Cephalotaxine, featuring a Pauson-khand reaction as the key transfomations has been conducted.