Symmetric Anion Mediated Dynamic Kinetic Asymmetric Knoevenagel Reaction for N-C and N-N Atropisomers Synthesis.

A symmetric anion mediated dynamic kinetic asymmetric Knoevenagel reaction was established as a general and efficient method for accessing both N-C and N-N atropisomers. The resulting highly enantio-pure pyridine-2,6(1H,3H)-diones exhibit diverse structures and functional groups. The key to excellent regio- and remote enantiocontrol could be owed to the hydrogen bond between the enolate anion and triflamide block of the organocatalyst. This connected the enolate anion and iminium cation by a chiral backbone. The mechanism investigation via control experiments, correlation analysis, and density functional theory calculations further revealed how the stereochemical information was transferred from the catalyst into the axially chiral pyridine-2,6(1H,3H)-diones. The synthetic applications also demonstrated the reaction's potential.

Regio- and Atroposelective Ring-Opening of 1H-Benzo[4,5]oxazolopyridinones.

The development of new methods for regio- and stereoselective activation of C-O bonds in ethers holds significant promise for synthetic chemistry, offering advantages in terms of environmental sustainability and economic efficiency. Moreover, the C-N atropisomers represent a fascinating and crucial chiral system, extensively found in natural products, pharmaceutical leads, and the frameworks of advanced materials. In this work, we have introduced a nickel-catalyzed regio- and enantioselective carbon-oxygen arylation reaction for atroposelective synthesis of N-arylisoquinoline-1,3(2H,4H)-diones. The high regioselectivity of C-O cleavage benefits from the high stability of the in situ formed (amido)ethenolate via oxidative addition. Additionally, the self-activation of the aryl C-O bond facilitates the reaction under mild conditions, leading to outstanding enantioselectivities. The diverse post-functionalizations of the axially chiral isoquinoline-1,3(2H,4H)-diones further highlighted the utility of this protocol in preparing valuable C-N atropisomers, including the chiral phosphine ligands.

Further developments of ß,γ-unsaturated α-ketoesters as versatile synthons in asymmetric catalysis.

ß,γ-Unsaturated α-ketoesters prove to be versatile organic synthons participating in diverse catalytic asymmetric transformations with the breathtaking development of organo-catalysis, new catalytic systems including ingenious chiral ligands as well as Lewis acid cations. The highly efficient creation of stereogenic centers with excellent enantioselectivity is not a surprise, but owes to the bidentate coordination of its unique 1,2-dicarbonyl motif to artful chiral messenger, establishing a rigid system for the precise chiral-identification of the attack. In the past five years, various reaction modes of ß,γ-unsaturated α-ketoesters have been developed, involving their multiple reaction sites, such as the carbon-carbon double bond (C=C), the carbonyl group (C=O), the entire C=C-C=O fragment, and the ester group. In this review, we summarize the state-of-the-art catalytic asymmetric reactions of ß,γ-unsaturated α-ketoesters, to provide an updated overview to chemists working in this and related fields, facilitating their discoveries in asymmetric catalysis, natural products synthesis, and drug development.

Hypervalent-Iodine-Mediated Carbon-Carbon Bond Cleavage and Dearomatization of 9H-Fluoren-9-ols.

A transition-metal-free synthesis of spiro compounds from 9H-fluoren-9-ols mediated by hypervalent iodine is reported. In this reaction, an unprecedented ß-carbon elimination of tertiary alkoxyliodine(III) to form new diaryliodonium salts is proposed. The obtained phenol intermediates undergo oxidative dearomatization to furnish a class of oxo-spiro compounds. This domino reaction significantly increases the complexity of these molecules and shows excellent regio- and stereoselectivity.

Cu-Catalyzed Enantioselective Atropisomer Synthesis via Thiolative Ring Opening of Five-Membered Cyclic Diaryliodoniums.

A Cu-catalyzed asymmetric thiolative ring opening reaction of five-membered diaryliodonium salts and potassium thioates for the synthesis of atropisomeric 2'-iodo-[1,1'-biphenyl]-2-yl thioates was realized. The optimal catalytic system, Cu(CH3CN)4PF6/(Ph)-bis(oxazoline), showed the best performance with respect to both yields and stereocontrol. Finally, the utility of these products was briefly demonstrated by the synthesis of an axially chiral P,S-ligand.

Palladium-catalyzed intramolecular asymmetric C-H functionalization/cyclization reaction of metallocenes: an efficient approach toward the synthesis of planar chiral metallocene compounds.

A palladium-catalyzed asymmetric synthesis of planar chiral metallocene compounds is reported. The reaction stereoselectively functionalized one of the ortho C-H bonds of Cp rings by intramolecular cyclization to form indenone derivatives in high yields with excellent enantioselectivity. The mild set of reaction conditions allowed a wide variety of chiral metallocene compounds to be synthesized with broad functional group tolerance. The influences of preinstalled chiralities on the other Cp-ring were also investigated.