This work describes gold-catalyzed additions of vinyldiazo ketones to N-(o-alkynylphenyl)­imines to yield 3-(furan-2-ylmethyl)-1H-indoles involving skeletal rearrangement; these new catalytic reactions are applicable to a wide range of substrates. We postulate a new mechanism involving an initial addition of diazo ketones to azomethine ylide intermediates to yield gold-containing N-alkylated indole intermediates that undergo proton-induced 1,3-group migrations, generating azallyl gold and allylic cation pairs.

One-pot synthesis of 5,6-dihydroindolo[2,1-a]isoquinolines from gold-catalyzed annulations between N-(oalkynylphenyl)imines and α-diazo esters is described. This cascade reaction involves an initial attack of the diazo ester at the imine to form cis-aziridine, followed by stereoselective [3 + 3]-annulations with the tethered arylalkyne. We have employed this new catalysis to prepare one bioactive 5,6-dihydroindolo[2,1-a]isoquinoline molecule.

With the relay process of Ag(I)/Au(I) catalysts, a one-pot synthesis of skeletally rearranged (1-hydroxymethylidene)indene derivatives from 2-alkynylbenzaldehydes and α-diazo esters is described. This cascade sequence involves Au(I)-catalyzed 5-endo-dig attack of highly enolizable aldehydes at the tethered alkynes, leading to carbocyclizations with a formal 1,3-hydroxymethylidene transfer. On the basis of density functional theory calculations, the mechanism likely involves formation of cyclopropylgold carbenes, followed by an appealing 1,2-cyclopropane migration.

Gold(I)-catalyzed reactions between 1-(1-alkynyl) cyclopropyl ketones and vinyldiazo ketones to produce substituted [(furan-3-yl)ethyl]-1H-pyrazol-5-yl)methanones are described. In this reaction sequence, we postulate vinyldiazo ketones to undergo a thermal cyclization to produce pyrazole intermediates that attack gold-containing all-carbon 1,4carbon dipoles to afford the observed products. An atypical N(1)-regioselectivity is also rationalized in this reaction model.