| Summary: | 博士 === 國立清華大學 === 化學系 === 105 === This dissertation describes development of new synthetic organic transformations by using gold, platinum or copper metal salts. The use of these metals enables mild, selective and efficient oxidative transformations of readily available substrates to wide range of synthetically useful nitrogen, oxygen and sulfur containing complex organic molecules. For better understanding the thesis is divided into four chapters.
The first chapter deals with the regiocontrolled hydrations of 1-aryl-3-en-1-ynes with suitable Au(I) and Pt(II), giving 3-en-1-ones and 2-en-1-ones selectively. Herein, we also develop one-pot synthesis of allylic and homoallylic alcohols from these 3-en-1-ynes, through in situ reductions of two ketone products. Our experimental data indicates that the sizes of catalysts play an important role.
The second chapter deals with the gold-catalyzed reactions of 1,6-enynes with N-hydroxyanilines to generate kinetically unstable trisubstituted nitrones. Such transient species are efficiently trapped with tethered alkenes to achieve stereospecific cycloadditions. Notably, these annulations involve an atypical N-attack of hydoxyamines at gold--alkynes. Our data reveal that most propargyl ethers show the O-attack selectivity, whereas allyl propargyl ether proceeds exclusively through the N-attack selectivity. This alkene-directed chemoselectivity is postulated to accelerate the protodeauration by an alkene coordination to gold.
The third chapter describes an atypical pathway in the gold-catalyzed intermolecular oxidations of ketonylalkynes with N-hydroxyanilines; this oxidation initially involves formation of an oxonium species that is subsequently attacked by N-hydroxyaniline, further leading to oxoamination products. This path is strongly supported by 18O-labeling experiments. In one control experiment, our resulting 2-aminoindenones were alternatively produced from the same ketonylalkynes, 8-methylquiniline oxide and aniline, but the efficiency was low.
The fourth chapter presents copper-catalyzed oxidative coupling reactions of tetrahydroisoquinolines with cyclic ethers. These reactions are initiated by SET from a tertiary amine to form an iminium ion which is coupled with alkyl radical to form C1-etherized tetrahydroisoquinoline. This method could open the possibility to design coupling reactions with substrates of low nucleophilicity but reactivity toward carbon radicals.
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