Ligand‐Controlled Regiodivergence in Nickel‐Catalyzed Hydroarylation and Hydroalkenylation of Alkenyl Carboxylic Acids**

Depending on the reactant property and reaction mechanism, one major regioisomer can be favored in areaction that involves multiple active sites.H erein, an orthogonal regulation of nucleophilic and electrophilic sites in the regiodivergent hydroamination of isoprene with indazoles is demonstrated. Under Pd-hydride catalysis,t he 1,2-or 4,3insertion pathway with respect to the electrophilic sites on isoprene could be controlled by the choice of ligands.Interms of the nucleophilic sites on indazoles,t he reaction occurs at either the N 1-o rN 2-position of indazoles is governed by the acid co-catalysts.P reliminary experimental studies have been performed to rationalizet he mechanism and regioselectivity. This study not only contributes ap ractical tool for selective functionalization of isoprene,b ut also provides ag uide to manipulate the regioselectivity for the N-functionalization of indazoles.

Orthogonal Regulation of Nucleophilic and Electrophilic Sites in Pd‐Catalyzed Regiodivergent Couplings between Indazoles and Isoprene

Jiang

Zhang

et al. 2021

Structurally Diverse Bench‐Stable Nickel(0) Pre‐Catalysts: A Practical Toolkit for In Situ Ligation Protocols**

Kim

Rubel

et al. 2023

Self Cite

A flurry of recent research has centered on harnessing the power of nickel catalysis in organic synthesis. These efforts have been bolstered by contemporaneous development of well-defined nickel (pre)catalysts with diverse structure and reactivity. In this report, we present ten different bench-stable, 18-electron, formally zero-valent nickel-olefin complexes that are competent pre-catalysts in various reactions. Our investigation includes preparations of novel, benchstable Ni(COD)(L) complexes (COD = 1,5-cyclooctadiene), in which L = quinone, cyclopentadienone, thiophene-Soxide, and fulvene. Characterization by NMR, IR, single-crystal X-ray diffraction, cyclic voltammetry, thermogravimetric analysis, and natural bond orbital analysis sheds light on the structure, bonding, and properties of these complexes. Applications in an assortment of nickel-catalyzed reactions underscore the complementary nature of the different precatalysts within this toolkit.

Catalytic Ring Expanding Difluorination: An Enantioselective Platform to Access β,β‐Difluorinated Carbocycles

Ruyet,

Roblick,

Häfliger

et al. 2024

Cyclic β,β‐difluoro‐carbonyl compounds have a venerable history as drug discovery leads, but limitations in the synthesis arsenal continue to impede chemical space exploration. This challenge is particularly acute in the arena of fluorinated medium rings where installing the difluoromethylene unit subtly alters the ring conformation by expanding the internal angle (∠C‐CF2‐C > ∠C‐CH2‐C): this provides a handle to modulate physicochemistry (e.g. pKa). To reconcile this disparity, a highly modular ring expansion has been devised that leverages simple α,β‐unsaturated esters and amides, and processes them to one‐carbon homologated rings with concomitant geminal difluorination (6 to 10 membered rings, up to 95% yield). This process is a rare example of the formal difluorination of an internal alkene and is enabled by sequential I(III)‐enabled O‐activation. Validation of enantioselective catalysis in the generation of unprecedented medium ring scaffolds is reported (up to 93:7 e.r.) together with X‐ray structural analyses and product derivatization.