Gold-catalyzed (4 + 2)-annulations between α-alkyl alkenylgold carbenes and benzisoxazoles with reactive alkyl groups.

This work reports new (4 + 2)-annulations of α-alkyl vinylgold carbenes with benzisoxazoles to afford 3,4-dihydroquinoline derivatives with high -stereoselectivity. The annulations are operable with carbenes in both acyclic and cyclic forms. This reaction sequence involves an initial formation of imines from α-alkylgold carbenes and benzisoxazoles, followed by a novel carbonyl-enamine reaction to yield 3,4-dihydroquinoline derivatives.

Brønsted Acids Enable Three Molecular Rearrangements of One 3-Alkylidene-2H-1,2-oxazine Molecule into Distinct Heterocyles.

This work describes three different strategies to structurally rearrange one 3-alkylidene-2H-1,2-oxazine molecule into three distinct heterocycles using HOTf, propiolic acid, and silica gel, respectively. The mechanisms of these rearrangement reactions involve three independent routes, including (i) Brønsted acid catalysis, (ii) a synergetic action of Brønsted acids and anions, (iii) a surface-directed chemoselectivity.

Gold-Catalyzed N,O-Functionalizations of 6-Allenyl-1-ynes with N-Hydroxyanilines To Construct Benzo[b]-azepin-4-one Cores.

Gold-catalyzed reactions of 6-allen-1-ynes with N-hydroxyanilines afford thermally stable benzoazepin-4-ones in anti-selectivity; these anti-configured products are easily isomerized to their syn-isomers on a silica column. The mechanism of reactions likely involve initial nitrone/allene cycloadditions, followed by skeletal rearrangement of resulting intermediates.

Gold-catalyzed Intermolecular Oxidations of 2-Ketonyl-1-ethynyl Benzenes with N-Hydoxyanilines to Yield 2-Aminoindenones via Gold Carbene Intermediates.

Gold-catalyzed oxidations of 2-ketonyl-1-ethynyl benzenes with N-hydroxyanilines yield 2-aminoindenone derivatives efficiently. Experimental data suggests that this process involves an α-oxo gold carbene intermediate, generated from the attack of N-hydroxyaniline on furylgold carbene intermediate, rather than the typical attack of oxidants on π-alkynes.

Regioselective hydrations of 1-aryl-3-en-1-ynes using gold and platinum catalysts: selective production of 2-en-1-ones and 3-en-1-ones.

Regiocontrolled hydrations of 1-aryl-3-en-1-ynes have been accomplished with IPrAuOTf and PtCl2/CO to yield 3-en-1-ones and 2-en-1-ones efficiently; our experimental data indicates that the sizes of catalysts play an important role.