Gold-catalysed [4+3]- and [4+2]-annulations of 3-substituted 3-en-1-ynamides with isoxazoles were achieved with Au(i) and Au(i)/Zn(ii) catalysts respectively.

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.

Cu(II)-catalyzed [4+2]-cycloadditions occur between Cu−benzopyryliums and substituted isoxazoles with the regioselectivity on the C(3,4)-carbons of isoxazoles. We postulate that a prior coordination of isoxazoles with Cu(OAc) 2 increases the π-bond character of the C(3,4) carbons to become an effective 2π-donor. In this reaction sequence, 3,5-disubstituted isoxazoles yield α,γ-dicarbonylnaphthalenes whereas, 5-substituted isoxazoles deliver α,γdicarbonyl-β-aminonaphthalenes. For unsubstituted isoxazole, its cycloaddition chemoselectivity is switched to the C(4,5)addition regioselectivity to yield α-carbonyl-γ-cyanonaphthalene derivatives.

Gold-catalyzed 1,4-carbooxygenations of 3-en-1-ynamides with allylic alcohols andpropargylic alcohols yield a,b-unsaturated amidest hrough non-Claisenp athways;t he mechanisms involve ionization of the initial gold enol ethers to form Cbound gold dienolates that capture allylicorpropargylic cations to yield the observedp roducts. Our 18 O-labeling experiments exclude ad irect gold-catalyzed allylation or propargylation on these 3-en-1ynamides.

Three distinct strategies for catalytic annulations between ynamides and 1‐yn‐3‐ols are described; the resulting carbo‐ and heterocycles were produced efficiently in one‐pot operations using a gold catalyst. The chemoselectivities of these annulations are controlled by variations of the substituents of the ynamides and the 1‐yn‐3‐ols. This reaction sequence involves initial alkoxylations of ynamides, followed by Claisen rearrangement of propargylic enol ethers, and ends with 6‐endo‐trig cyclizations of 1‐allenyl‐5‐amide intermediates. Among these cascade annulations, the cyclizations of 5‐allenyl‐1‐amides to yield 5,6‐dihydro‐2‐pyranones and 6‐alkylenecyclohex‐2‐ene‐1‐carboxamides are unprecedented in the literature.magnified image