不对称的猫alysis

Controlling various selectivities in radical reactions presents both formidable challenges and great opportunities. Now, Co(II)-based metalloradical catalysis has enabled the concurrent control of multiple convergences and selectivities in intermolecular radical allylic C−H amination. The reaction provides access to valuable chiral α-tertiary amines directly from an isomeric mixture of alkenes.

Chiral α-acylatedN-heterocycles are commonly found in pharmaceutical drugs, natural products, and catalysts for asymmetric synthesis. Here, the authors describe a cooperative nickel/photoredox catalysis strategy for the site- and enantioselective cross-coupling of saturated azacycles and carboxylic acids to access such valuable heterocyclic molecules.

A combined copper- and palladium-catalysed atropselective arylboration of alkynes is reported. This method uses B₂pin₂and sterically hindered aryl bromides for the stereoselective and regioselective synthesis of axially chiral tetrasubstituted alkenylboronates. Mechanistic studies reveal that the stereocontrol originates from a higher-order palladium intermediate.

Asymmetric systems for catalytic carbohydrate functionalization are mostly limited to chiral copper complexes and organocatalysts. Now, a synergistic chiral Rh(I)- and organoboron-catalysed site-selective functionalization of carbohydrate polyols has been developed, giving stereocontrolled access to biologically relevant arylhydronaphthalene glycosides. Enantio-, diastereo-, regio- and anomeric control and dynamic kinetic resolution were found to be concomitantly operative.

Heteroatom–heteroatom cross-couplings have so far remained elusive. Now, a copper-catalysed enantioselective S–O cross-coupling of diverse diols or triols with sulfonyl chlorides has been realized via a single-electron reductive elimination manifold. The reaction provides access to value-added chiral C₃building blocks and inositol phosphates through enantioselective desymmetrization of biomass-derived alcohols.

Simultaneous stereochemical control of two vicinal C(sp³) stereocentres from two reaction partners is challenging. Now, this is achieved in a nickel-catalysed enantio- and diastereoselective cross-coupling reaction of internal alkenes with racemic alkyl bromides.