Ruthenium-catalyzed (2 + 2) intramolecular cycloaddition of allenenes.

We report a ruthenium-catalyzed (2 + 2) intramolecular cycloaddition of allenes and alkenes. We have found that the use of the ruthenium complex RuH(2)Cl(2)(P(i)Pr(3))(2), which has previously gone unnoticed in catalytic applications, is crucial for the observed reactivity. The reaction proceeds under mild conditions and is fully diastereoselective, providing a practical entry to a variety of bicyclo[3.

Palladium-catalyzed [3C + 2C + 2C] cycloaddition of enynylidenecyclopropanes: efficient construction of fused 5-7-5 tricyclic systems.

We report a Pd-catalyzed intramolecular [3C + 2C + 2C] cycloaddition between alkylidenecyclopropanes, alkynes and alkenes. The method provides synthetically relevant 5-7-5 tricyclic structures, with good chemoselectivity and complete diastereoselectivity.

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.