Gold-catalyzed oxidative couplings of two indoles and one α-cyano gold carbene to form bis(indolyl)methane derivatives are described. Two different indoles are compatible with these reactions to provide reasonable yields. A plausible mechanism is postulated to rationalize the experimental data including product distributions, DO labeling, and the significant effects of gold catalysts and cyano groups.
Gold-catalyzed 1,2-iminonitronation of propiolate derivatives with nitrosoarenes to give α-imidoyl nitrones is described; this new reaction is applicable to diverse propiolate derivatives and nitrosoarenes.
Gold-catalyzed oxidations of thioalkynes with 8-methylquinoline oxides afford 2-phenylthioketenes that can be trapped efficiently with alcohols. The synthetic utility is manifested by terminal and internal thioalkynes over a wide scope, bearing esters, ketones, alkyl, and oxime substituents. Our density functional theory calculations suggest that gold-catalyzed oxidations of terminal and internal thioalkynes with 8-methylquinoline oxides generate gold-bound ketene intermediates without the intermediacy of α-oxo gold carbene.
This work reports gold-catalyzed oxidative alkenylations of quinoline N-oxides with propargyl aryl thioethers to afford 3-hydroxy-1alkylidenephenylthiopropan-2-one via a 1,3-sulfur group migration. The mechanism of this reaction is postulated to involve an α-oxo gold carbene intermediate followed by formation of a four-membered sulfonium ring that is ring-opened by one H 2 O to form a gold enolate. A final condensation of this enolate with a second quinoline N-oxide delivers an alkenylation product accompanied by a 1,3-sulfur shift.
Gold-catalyzed imination/Mannich reaction cascadeso nr eadily available 3-en-1-ynamides enable the diastereoselectives ynthesis of 1,5-iminoamino compounds in ao ne-pot operation. The reactions workw ell with diversified3 -en-1-ynamides,a ldehydes anda nilines with good to excellent diastereoselectivities.O ur control experiments indicate gold-catalyzed aminations of 3-en-1-ynamides to yield a-imino allylgold intermediates that react subsequently with iminiums to implement the Mannich reactions stereoselectively.T he reactions proceed with anti-selectivity for those 3-en-1-ynamides bearing acyclic alkenes whereas syn-selectivity is seen for theirc ycloalkene-baseda nalogues.A n open-transition state can satisfactorily rationalize these observeds tereoselectivities based on an antiperiplanar conformation.
Gold-catalyzed [3+2]-annulations of α-aryl diazonitriles with ynamides and allenamides yield 1-amino-1H-indenes in two distinct pathways; the success of these annulations relies on the high electrophilicity of α-cyano arylgold carbenes to activate an ionic pathway.
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