Picolinamide Ligands: Nickel-Catalyzed Reductive Cross-Coupling of Aryl Bromides with Bromocyclopropane and Beyond

The arylcyclopropane motif as the combination of aryl and cyclopropyl ring systems can be found in an increasing amount of approved and investigational drugs. Herein, we have developed a mild, efficient nickel-catalyzed reductive cross-coupling protocol, featuring a simple Ni(II) precatalyst and a novel picolinamide NN₂ pincer ligand. A variety of (hetero)aryl bromides could successfully couple with cyclopropyl bromide to furnish the valued arylcyclopropanes in good to excellent yields. This method is applicable to other alkyl bromides as well. Notably, the reaction is tolerant of a broad range of functionalities including free amines. Furthermore, the synthesis of several significant intermediates of bioactive molecules was achieved in grams, proving the practicability of this method.

Ni-Catalyzed Regio- and Stereoselective Alkylarylation of Unactivated Alkenes in γ,δ-Alkenylketimines

We disclose a Ni-catalyzed vicinal alkylarylation of unactivated alkenes in γ,δ-alkenylketimines with aryl halides and alkylzinc reagents. The reaction produces γ-C(sp3)-branched δ-arylketones with the construction of two new C(sp3)-C(sp3) and C(sp3)-C(sp2) bonds. Electron-deficient alkenes play crucial dual roles as ligands to stabilize reaction intermediates and to increase catalytic rates for the formation of C(sp3)-C(sp3) bonds. This alkene alkylarylation reaction is also effective for secondary alkylzinc reagents and internal alkenes, and proceeds with a complete regio- and stereocontrol, affording products with up to three contiguous all-carbon all-cis secondary stereocenters.

An Expedient Route to 9-arylmethylanthracene Derivatives via Tandem Ni-catalyzed Alkene Dicarbofunctionalization and Acid-promoted Cyclization-aromatization

We report a nickel-catalyzed one pot synthesis of 9-arylmethylanthracene motifs, which find applications in medicinal and material chemistry. In this synthesis, we apply three component alkene dicarbofunctionalization of 2-vinylaldimines with aryl iodides and arylzinc reagent to generate a 1,1,2-diarylethyl scaffold, which then undergoes an acidpromoted cyclization followed by aromatization to furnish 9-arylmethylanthracene cores. With the new method, a number of differently-substituted 9-arylmethylanthracene derivatives can be synthesized in good yields.