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1. Fe-catalyzed three-component dicarbofunctionalization of unactivated alkenes with alkyl halides and Grignard reagents

   https://doi.org/10.1039/D0SC02127J  

   Liu, Lei; Lee, Wes; Youshaw, Cassandra R.; Yuan, Mingbin; Geherty, Michael B.; Zavalij, Peter Y.; Gutierrez, Osvaldo (August 2020, Chemical Science)

   null (Ed.)

   A highly chemoselective iron-catalyzed three-component dicarbofunctionalization of unactivated olefins with alkyl halides (iodides and bromides) and sp 2 -hybridized Grignard reagents is reported. The reaction operates under fast turnover frequency and tolerates a diverse range of sp 2 -hybridized nucleophiles (electron-rich and electron-deficient (hetero)aryl and alkenyl Grignard reagents), alkyl halides (tertiary alkyl iodides/bromides and perfluorinated bromides), and unactivated olefins bearing diverse functional groups including tethered alkenes, ethers, protected alcohols, aldehydes, and amines to yield the desired 1,2-alkylarylated products with high regiocontrol. Further, we demonstrate that this protocol is amenable for the synthesis of new (hetero)carbocycles including tetrahydrofurans and pyrrolidines via a three-component radical cascade cyclization/arylation that forges three new C–C bonds. 

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2. Recent developments in nickel-catalyzed intermolecular dicarbofunctionalization of alkenes

   https://doi.org/10.1039/c9sc06006e  

   Derosa, Joseph; Apolinar, Omar; Kang, Taeho; Tran, Van T.; Engle, Keary M. (May 2020, Chemical Science)

   Nickel-catalyzed three-component alkene difunctionalization has rapidly emerged as a powerful tool for forging two C–C bonds in a single reaction. Building upon the powerful modes of bond construction in traditional two-component cross-coupling, various research groups have demonstrated the versatility of nickel in enabling catalytic 1,2-dicarbofunctionalization using a wide range of carbon-based electrophiles and nucleophiles and in a fully intermolecular fashion. Though this area has emerged only recently, the last few years have witnessed a proliferation of publications on this topic, underscoring the potential of this strategy to develop into a general platform that offers high regio- and stereoselectivity. This minireview highlights the recent progress in the area of intermolecular 1,2-dicarbofunctionalization of alkenes via nickel catalysis and discusses lingering challenges within this reactivity paradigm. 

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3. Hemilabile and Redox‐Active Quinone Ligands Unlock sp ³ ‐Rich Couplings in Nickel‐Catalyzed Olefin Carbosulfenylation

   https://doi.org/10.1002/anie.202411870  

   Li, Zi‐Qi; Alturaifi, Turki M; Cao, Yilin; Joannou, Matthew V; Liu, Peng; Engle, Keary M (December 2024, Angewandte Chemie International Edition)

   Abstract A three‐component coupling approach toward structurally complex dialkylsulfides is described via the nickel‐catalyzed 1,2‐carbosulfenylation of unactivated alkenes with organoboron nucleophiles and alkylsulfenamide (N−S) electrophiles. Efficient catalytic turnover is facilitated using a tailored N−S electrophile containing anN‐methyl methanesulfonamide leaving group, allowing catalyst loadings as low as 1 mol %. Regioselectivity is controlled by a collection of monodentate, weakly coordinating native directing groups, including sulfonamides, amides, sulfinamides, phosphoramides, and carbamates. Key to the development of this transformation is the identification of quinones as a family of hemilabile and redox‐active ligands that tune the steric and electronic properties of the metal throughout the catalytic cycle. Density functional theory (DFT) results show that the duroquinone (DQ) ligand adopts different coordination modes in different stages of the Ni‐catalyzed 1,2‐carbosulfenylation‐binding as an η⁶capping ligand to stabilize the precatalyst/resting state and prevent catalyst decomposition, binding as an X‐type redox‐active durosemiquinone radical anion to promote alkene migratory insertion with a less distorted square planar Ni(II) center, and binding as an L‐type ligand to promote N−S oxidative addition at a relatively more electron‐rich Ni(I) center. 

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4. Photoinduced 1,2-dicarbofunctionalization of alkenes with organotrifluoroborate nucleophiles via radical/polar crossover

   https://doi.org/10.1039/d1sc02547c  

   Cabrera-Afonso, María Jesús; Sookezian, Anasheh; Badir, Shorouk O.; El Khatib, Mirna; Molander, Gary A. (July 2021, Chemical Science)

   null (Ed.)

   Alkene 1,2-dicarbofunctionalizations are highly sought-after transformations as they enable a rapid increase of molecular complexity in one synthetic step. Traditionally, these conjunctive couplings proceed through the intermediacy of alkylmetal species susceptible to deleterious pathways including β-hydride elimination and protodemetalation. Herein, an intermolecular 1,2-dicarbofunctionalization using alkyl N -(acyloxy)phthalimide redox-active esters as radical progenitors and organotrifluoroborates as carbon-centered nucleophiles is reported. This redox-neutral, multicomponent reaction is postulated to proceed through photochemical radical/polar crossover to afford a key carbocation species that undergoes subsequent trapping with organoboron nucleophiles to accomplish the carboallylation, carboalkenylation, carboalkynylation, and carboarylation of alkenes with regio- and chemoselective control. The mechanistic intricacies of this difunctionalization were elucidated through Stern–Volmer quenching studies, photochemical quantum yield measurements, and trapping experiments of radical and ionic intermediates. 

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5. Development and Mechanistic Studies of the Iridium‐Catalyzed C−H Alkenylation of Enamides with Vinyl Acetates: A Versatile Approach for Ketone Functionalization

   https://doi.org/10.1002/anie.202107331  

   Zhou, Bo; Qi, Xiaotian; Liu, Peng; Dong, Guangbin (August 2021, Angewandte Chemie International Edition)

   Abstract Ketone functionalization is a cornerstone of organic synthesis. Herein, we describe the development of an intermolecular C−H alkenylation of enamides with the feedstock chemical vinyl acetate to access diverse functionalized ketones. Enamides derived from various cyclic and acyclic ketones reacted efficiently, and a number of sensitive functional groups were tolerated. In this iridium‐catalyzed transformation, two structurally and electronically similar alkenes—enamide and vinyl acetate—underwent selective cross‐coupling through C−H activation. No reaction partner was used in large excess. The reaction is also pH‐ and redox‐neutral with HOAc as the only stoichiometric by‐product. Detailed experimental and computational studies revealed a reaction mechanism involving 1,2‐Ir‐C migratory insertion followed bysyn‐β‐acetoxy elimination, which is different from that of previous vinyl acetate mediated C−H activation reactions. Finally, the alkenylation product can serve as a versatile intermediate to deliver a variety of structurally modified ketones. 

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