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Study of Approaches on Homogeneous Gold Catalysts in the Syntiesis of Pyrrolidin-3-one and α-acetoxy Ketones

Author: ChenHui
Tutor: XiangJianNan
School: Hunan University
Course: Biomedical Engineering
Keywords: gold catalyst homogeneous gold catalysis α-oxo gold carbene pyrrolidin-3-one α-acetoxy ketones
CLC: R914.5
Type: Master's thesis
Year: 2013
Downloads: 4
Quote: 0
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Abstract


Gold catalyst has been applied in homogeneous catalysis reactions for a long time, andhomogeneous gold-catalyzed reactions have been a hot research area in organic chemistrytoday. Gold complex is a soft Lewis acid, and possesses the properties of π acid. It canactivate π bonds efficiently and then react with various nucleophilic reagents. Nitrogen oxidesare an important class of nucleophilic oxidant in homogeneous gold catalytic reactions. It canoccur nucleophilic reaction with alkynyl group that activated by gold catalyst, and generate animportant α-oxo gold carbene intermediate. The α-oxo gold carbenoids have a high reactivity.It can undergo nucleophilic attack by imine, arene and migrating hydride tandem reactions,and leading to the construction of new skeletons.Heteroatom and hecerocycles are the molecules that possessing heteroatons (N, O, S, Siand halgen, etc). In the existing drugs, compounds containing heterocyclic or heteroatomoccupy the dominant position. Most of the drugs are built up based on the heterocycliccompound. Hence, how to get heteroatom compound we needed from avaliable materials hasbecome a new direction for efforts by scientists.In this paper, we studied the application of the α-oxo gold carbene intermediate in theconstruction of heteroatom and heterocyclic compounds by making use of the high activity ofα-oxo gold carbene intermediate. The work includes the following two aspects:1. A general solution for the synthesis of pyrrolidin-3-one has been developed. In theoptimization process, we have studed the effect of protecting group, substituent group, goldcatalyst, oxidant, acid and reaction temperature on the model reaction. With5%Et3PAuNTf2catalyst,1.5equiv of2,4-dichloro-pyridine nitrogen oxygen, and1.2equiv of MsOHdissolved in dichloroethane and react under0°C. The substate terminal alkynylamine for goldcatalytic is prepared by cheap and readily available aldehyde from a two step reactions. Andthen the terminal alkynylamine is transformed to a series of pyrrolidin-3-one derivatives.Compared with the conventional synthetic method, the present synthetic route is short andwide applicability of the substate. Meanwhile the reaction generally has a high yield and mildconditions. The structure of the products have all characterized by1H NMR and13C NMR.2. Another homogeneous gold catalyst system has been developed to synthesis α-acetoxyketones. We have examined the impact of the catalyst, oxidant and the reaction timerespectively by establised a model reaction using phenylacetylene as the substate, and therebyobtained the optimum reaction conditions. With5%Ph3PAuNTf2catalyst,1.5equiv of 8-methyl-quinoline nitrogen oxygen, and1.2equiv of MsOH dissolved in ethyl acetate andreact under room temperatrue for8hours. With terminal alkyne and ethyl acetate as rawmaterials, α-acetoxy ketones with various substituents are obtained through the additionreaction of ester group to α-oxo gold carbene intermediate. Ethyl acetate in this reaction is notonly the reactant, but also the reaction solvent. The reaction does not require anhydrousanaerobic operation and the post-processing is simple, and favorably a high yield. Thestructure of the products have all characterized by1H NMR and13C NMR.In this paper, we have built two catalytic system to synthesize hetero atom-containingcompounds. These new catalytic system has a good applicability to terminal alkyne substratematerial. It can carried on smoothly in mild cinditions,and thus provides a new way forsynthesizing hetero atom-containing compounds.

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