Access to chiral dihydrophenanthridines via a palladium(0)-catalyzed Suzuki coupling and C-H arylation cascade reaction using new chiral-bridged biphenyl bifunctional ligands

A class of chiral-bridged biphenyl phosphine-carboxylate bifunctional ligands CB-Phos has been developed and successfully applied to Pd(0)-catalyzed single enantioselective C-H arylation and a one pot cascade reaction involving Suzuki cross-coupling and C-H arylation. The catalytic system provides a new and convenient way for the synthesis of versatile chiral dihydrophenanthridines with rich structures and broad functional group tolerance. Good to excellent yields with high enantioselectivities were generally achieved. The reaction mechanism of the cascade reaction was also preliminarily discussed.

Enantioenriched 1,4-Benzoxazepines via Chiral Brønsted Acid-Catalyzed Enantioselective Desymmetrization of 3-Substituted Oxetanes

Herein, we present a highly enantioselective desymmetrization of 3-substituted oxetanes enabled by a confined chiral phosphoric acid. This metal-free process allows effective access to chiral seven-membered 1,4-benzoxazepines with a high degree of enantiocontrol, under mild reaction conditions. The developed synthetic strategy tolerates a broad substrate scope and demonstrates its synthetic utility in various enantioselective product transformations, thus proving its effectiveness in diverse scenarios.

Iridium-Catalyzed Intramolecular Asymmetric Allylic Etherification of Pyrimidinemethanols: Enantioselective Construction of Multifunctionalized Pyrimidine-Fused Oxazepines

An iridium-catalyzed intramolecular asymmetric allylic etherification of pyrimidinemethanols is described. In the presence of chiral-bridged biphenyl phosphoramidite ligand L3 and triethylborane, this process provided a class of novel pyrimidine-fused oxazepanes in up to 99% yield with 99.5% enantiomeric excess. The work addresses the challenge of insufficient nucleophilicity of aliphatic alcohols for allyl substitution and indicates the vital value of chiral-bridged biphenyl phosphoramidites. Various multifunctionalized transformations of the products further demonstrate the robust synthetic utility of this methodology.

Preparation of a Montmorillonite-Modified Chitosan Film-Loaded Palladium Heterogeneous Catalyst and its Application in the Preparation of Biphenyl Compounds

The natural polymer chitosan was modified with polyvinyl alcohol to enhance the mechanical properties of the membrane, and then, the montmorillonite-modified chitosan-loaded palladium catalyst was prepared using the excellent coordination properties of montmorillonite. The results showed that the catalyst has good tensile strength, thermal stability, catalytic activity, and recycling performance and is a green catalytic material with industrial application potential.