Enantioconvergent synthesis of chiral fluorenols from racemic secondary alcohols Pd(ii)/chiral norbornene cooperative catalysis.

An efficient protocol for the asymmetric synthesis of fluorenols has been developed through an enantioconvergent process enabled by Pd(ii)/chiral norbornene cooperative catalysis. This approach allows facile access to diverse functionalized chiral fluorenols with constantly excellent enantioselectivities, applying readily available racemic secondary -bromobenzyl alcohols and aryl iodides as the starting materials.

Catalytic Synthesis of Atropisomeric -Terphenyls with 1,2-Diaxes via Axial-to-Axial Diastereoinduction.

Herein, we report a modular and convergent strategy for the assembly of atropisomeric -terphenyls with 1,2-diaxes via palladium/chiral norbornene cooperative catalysis and axial-to-axial diastereoinduction. Readily available aryl iodides, 2,6-substituted aryl bromides, and potassium aryl trifluoroborates are used as the building blocks, laying the foundation for diversity-oriented synthesis of these scaffolds (46 examples). Other features include the unique axial-to-axial diastereoinduction mode, construction of two axes in a single operation, and step economy.

Kinetic Resolution of Tertiary Benzyl Alcohols via Palladium/Chiral Norbornene Cooperative Catalysis.

Herein we report a highly enantioselective kinetic resolution of tertiary benzyl alcohols via palladium/chiral norbornene cooperative catalysis. With simple aryl iodides as the resolution reagent, a wide range of readily available racemic tertiary benzyl alcohols are applicable to this method. Both chiral tertiary benzyl alcohols and benzo[c]chromene products are obtained in good to excellent enantioselectivities (selectivity factor up to 544).

Modular Dual-Tasked C-H Methylation via the Catellani Strategy.

We report a dual-tasked methylation that is based on cooperative palladium/norbornene catalysis. Readily available (hetero)aryl halides (39 iodides and 4 bromides) and inexpensive MeOTs or trimethylphosphate are utilized as the substrates and methylating reagent, respectively. Six types of "ipso" terminations can modularly couple with this "ortho" C-H methylation to constitute a versatile methylation toolbox for preparing diversified methylated arenes.

A palladium/norbornene cooperative catalysis to access N-containing bridged scaffolds.

A palladium/norbornene cooperative catalysis promoted annulation involving an ortho-C-H amination and intramolecular Heck cascade between aryl iodides and functionalized amination reagents is reported, thereby providing a highly convergent access to the unique N-containing bridged scaffolds: hexahydro-2,6-methano-1-benzazocine. The salient features of the reaction include its broad substrate scope (with respect to aryl iodides), its high step economy, and good chemoselectivity. Preliminary studies underscore the future promise of rendering this Catellani-type annulation enantioselective.

Alkylating Reagents Employed in Catellani-Type Reactions.

The Catellani reaction is a powerful strategy that allows the expeditious synthesis of highly substituted arenes, which are not easily accessible through traditional transition-metal-catalyzed cross-coupling reactions. This reaction utilizes the synergistic interplay of palladium and norbornene catalysis to facilitate sequential ortho-C-H functionalization and ipso termination of aryl iodides in a single operation. Since pioneering work by the group of Catellani in 1997, and later by the group of Lautens, this chemistry has attracted considerable attention from the synthetic chemistry community.

The Discovery of a Palladium(II)-Initiated Borono-Catellani Reaction.

Reported is a novel palladium(II)-initiated Catellani-type reaction that utilizes widely accessible aryl boronic acids as the substrates instead of aryl halides, thereby greatly expanding the existing scope of this powerful transformation. This borono-Catellani reaction was promoted by cooperative catalysis between Pd(OAc) and the inexpensive 5-norbornene-2-carbonitrile. Practicality is the striking feature of the reaction: it is run open to air at ambient temperature and no phosphine ligand is needed.

Palladium-catalyzed asymmetric cycloadditions of vinylcyclopropanes and in situ formed unsaturated imines: construction of structurally and optically enriched spiroindolenines.

A palladium-catalyzed (3 + 2) cycloaddition of vinyl cyclopropane and α,β-unsaturated imines generated in situ from aryl sulfonyl indoles is reported. The reaction proceeds with high diastereoselectivity to provide the optically enriched spirocyclopentane-1,3'-indolenines in up to 74% yield and with up to 97% ee, which contains an all-carbon quaternary center and two tertiary stereocenters. The reaction involves a first conjugate addition of the carbon anion of zwitterionic π-allylpalladium complex from vinyl cyclopropane to the in situ formed unsaturated imine followed by a palladium-catalyzed intramolecular C3-allylation of indole.