Enantioselective Silver and Amine Co-catalyzed Desymmetrizing Cycloisomerization of Alkyne-Linked Cyclohexanones.

A silver(I) and amine co-catalyzed desymmetrization of 4-propargylamino cyclohexanones for the direct enantioselective synthesis of 2-azabicyclo[3.3.1]nonanes is described.

Enantioselective desymmetrization of prochiral cyclohexanones by organocatalytic intramolecular Michael additions to α,β-unsaturated esters.

A new catalytic asymmetric desymmetrization reaction for the synthesis of enantioenriched derivatives of 2-azabicyclo[3.3.1]nonane, a key motif common to many alkaloids, has been developed.

Dual amine and palladium catalysis in diastereo- and enantioselective allene carbocyclization reactions.

A pyrrolidine and Pd catalyzed diastereoselective carbocyclization of aldehyde and ketone-linked allenes has been developed. The cooperative organo/metal-catalyzed cyclization reaction, which presumably proceeds via an enamine intermediate, is efficient and broad in scope. Also, it has been extended to a catalytic asymmetric variant using diarylprolinol-based organocatalysts to afford substituted cyclopentane and pyrrolidine reaction products in up to 82% ee.

Highly stereoselective modifications of peptides via Pd-catalyzed allylic alkylation of internal peptide amide enolates.

Pd-catalyzed allylations are excellent tools for stereoselective peptide modifications, showing several advantages compared to normal alkylations. Reactions of internal peptide amide enolates with Pd-allyl complexes proceed not only with high yields of up to 86%, they show also high regio- and diastereoselectivities (88-99%), giving rise to the trans-configured products. Therefore, this protocol is a powerful synthetic tool for the synthesis of natural product and drug molecules.

Stereoselective palladium-catalyzed allylic alkylations of peptide amide enolates.

Pd-catalyzed allylations are an excellent tool for stereoselective peptide modifications, being clearly superior to normal alkylations. The reactions proceed not only in high yield, but also high regio- and diastereoselectivities, and trans-products are formed exclusively. Therefore, this is a powerful synthetic tool for natural product and drug synthesis.

Gold-catalyzed hydrative carbocyclization of 1,5- and 1,7-allenynes mediated by pi-allene complex: mechanistic evidence supported by the chirality transfer of allenyne substrates.

We report PPh3AuCl/AgOTf-catalyzed hydrative carbocyclization of 1,5- and 1,7-allenynes to give cyclized ketones chemoselectively. In this transformation, hydration occurrs regioselectively at the C[triple bond]CPh carbon, accompanied by addition of the C[triple bond]CPh carbon to the two terminal allenyl carbons. This method is effective for the construction of a quaternary carbon center.

Gold-catalyzed [4+3]-annulation of oxabicyclic benzenes with 2-substituted allylsilanes through tandem allylation and cyclization.

This work reports new gold-catalyzed [4+3]-annulations of oxacyclic benzenes with 2-substituted allylsilanes through tandem allylation and cyclization; on the basis of experimental observations, we propose a mechanism involving the opening of the oxacyclic ring by a PPh3Au+-assisted SN2-attack of allylsilanes.

The skeletal rearrangement of gold- and platinum-catalyzed cycloisomerization of cis-4,6-dien-1-yn-3-ols: pinacol rearrangement and formation of bicyclo[4.1.0]heptenone and reorganized styrene derivatives.

With gold and platinum catalysts, cis-4,6-dien-1-yn-3-ols undergo cycloisomerizations that enable structural reorganization of cyclized products chemoselectively. The AuCl3-catalyzed cyclizations of 6-substituted cis-4,6-dien-1-yn-3-ols proceeded via a 6-exo-dig pathway to give allyl cations, which subsequently undergo a pinacol rearrangement to produce reorganized cyclopentenyl aldehyde products. Using chiral alcohol substrates, such cyclizations proceed with reasonable chirality transfer.

Ruthenium-catalyzed cyclization of 2-alkyl-1-ethynylbenzenes via a 1,5-hydrogen shift of ruthenium-vinylidene intermediates.

Catalytic cyclization of 2-alkyl-1-ethynylbenzene derivatives was implemented by TpRuPPh3(CH3CN)2PF6 (10 mol %) in hot toluene (105 degrees C, 36-100 h) to form 1-substituted-1H-indene and 1-indanone products; such cyclizations proceeded more efficiently for substrates bearing electron-rich benzenes. We propose that the cyclization mechanism involves a 1,5-hydrogen shift of initial metal-vinylidene intermediate.

Ruthenium-catalyzed cycloisomerization of cis-3-en-1-ynes to cyclopentadiene and related derivatives through a 1,5-sigmatropic hydrogen shift of ruthenium-vinylidene intermediates.

We report a new ruthenium-catalyzed cycloisomerization of unactivated cis-3-en-1-ynes, which produces substituted cyclopentadiene and related derivatives. The mechanism of this cyclization is proposed to involve a [1,5]-sigmatropic hydrogen shift of ruthenium-vinylidene intermediates on the basis of deuterium-labeling experiments.

A new ruthenium-catalyzed cleavage of a carbon-carbon triple bond: efficient transformation of ethynyl alcohol into alkene and carbon monoxide.

We report a new and efficient ruthenium-catalyzed reaction that transforms ethynyl alcohol into alkene and carbon monoxide. The most efficient catalysts are TpRu(PPh3)(CH3CN)2PF6 (10 mol %) and lithium triflate (20 mol %). The mechanism of this reaction was elucidated using an isotope-labeling experiment.