Mechanistic intricacies of gold-catalyzed intermolecular cycloadditions between allenamides and dienes.

The mechanism of the gold-catalyzed intermolecular cycloaddition between allenamides and 1,3-dienes has been explored by means of a combined experimental and computational approach. The formation of the major [4+2] cycloaddition products can be explained by invoking different pathways, the preferred ones being determined by the nature of the diene (electron neutral vs. electron rich) and the type of the gold catalyst (AuCl vs.

Theoretical study on intramolecular allene-diene cycloadditions catalyzed by PtCl2 and Au(I) complexes.

The intramolecular [4C+3C] cycloaddition reaction of allenedienes catalysed by PtCl(2) and several Au(I) complexes has been studied by means of DFT calculations. Overall, the reaction mechanism comprises three main steps: (i) the formation of a metal allyl cation intermediate, (ii) a [4C(4π)+3C(2π)] cycloaddition that produces a seven-membered ring and (iii) a 1,2-hydrogen migration process on these intermediates. The reaction proceeds with complete diastereochemical control resulting from a favoured exo-like cycloaddition.

Gold-catalyzed cycloadditions involving allenes: mechanistic insights from theoretical studies.

Allenes, owing to their special structural characteristics related to the presence of two π bonds in a formally strained manner, are particularly prone to undergo gold-activated reactions, particularly cycloaddition processes. Theoretical studies based on DFT calculations have been very useful to explain observed reactivities and advance mechanistic proposals.

Gold(I)-catalyzed intermolecular oxyarylation of alkynes: unexpected regiochemistry in the alkylation of arenes.

The reaction between acetylenes and sulfoxides, studied as a test case for gold-catalyzed intermolecular addition, provides the oxyarylation compounds 3 in good yields. Unpredictably, in all cases a single regioisomer arising from the electrophilic aromatic alkylation at the position adjacent to the sulfur atom is obtained instead of the expected Friedel-Crafts regioisomer. A new concerted mechanism based on DFT calculations is proposed to account for the products in this intermolecular gold(I)-catalyzed reaction.

Gold-catalyzed [4C+2C] cycloadditions of allenedienes, including an enantioselective version with new phosphoramidite-based catalysts: mechanistic aspects of the divergence between [4C+3C] and [4C+2C] pathways.

Gold(I) complexes featuring electron acceptor ligands such as phosphites and phosphoramidites catalyze the [4C+2C] intramolecular cycloaddition of allenedienes. The reaction is chemo- and stereoselective, and provides trans-fused bicyclic cycloadducts in good yields. Moreover, using novel chiral phosphoramidite-based gold catalysts it is possible to perform the reaction with excellent enantioselectivity.

Gold-catalyzed [4C+3C] intramolecular cycloaddition of allenedienes: synthetic potential and mechanistic implications.

Efficient at room temperature: The Au complex generated in situ from [(IPr)AuCl] and AgSbF(6) promotes the [4C+3C] intramolecular cycloaddition of allenes and dienes at room temperature, and in a particularly efficient and versatile manner. A DFT study on dimethylallenyl precursors agreed with the formation and cycloaddition of a metal-allyl cation intermediate, and points to the 1,2-hydride shift as the key rate-limiting step.