Nickel-Catalyzed Enantioselective Reductive Cross-Coupling Reactions

ACS Catalysis, Год журнала: 2020, Номер 10(15), С. 8237 - 8246

Опубликована: Июнь 24, 2020

Nickel-catalyzed reductive cross-coupling reactions have emerged as powerful methods to join two electrophiles. These proven particularly useful for the coupling of sec-alkyl electrophiles form stereogenic centers; however, development enantioselective variants remains challenging. In this Perspective, we summarize progress that has been made toward Ni-catalyzed reactions.

Язык: Английский

---

Applications of Halogen-Atom Transfer (XAT) for the Generation of Carbon Radicals in Synthetic Photochemistry and Photocatalysis

Chemical Reviews, Год журнала: 2021, Номер 122(2), С. 2292 - 2352

Опубликована: Дек. 9, 2021

The halogen-atom transfer (XAT) is one of the most important and applied processes for generation carbon radicals in synthetic chemistry. In this review, we summarize highlight aspects associated with XAT impact it has had on photochemistry photocatalysis. organization material starts analysis mechanistic then follows a subdivision based nature reagents used halogen abstraction. This review aims to provide general overview fundamental concepts main agents involved objective offering tool understand facilitate development new radical strategies.

Язык: Английский

---

Mechanisms of Nickel-Catalyzed Coupling Reactions and Applications in Alkene Functionalization

Accounts of Chemical Research, Год журнала: 2020, Номер 53(4), С. 906 - 919

Опубликована: Апрель 2, 2020

ConspectusNickel complexes exhibit distinct properties from other group 10 metals, including a small nuclear radius, high paring energy, low electronegativity, and redox potentials. These enable Ni catalysts to accommodate stabilize paramagnetic intermediates, access radical pathways, undergo slow β-H elimination. Our research program investigates how each of these fundamental attributes impact the catalytic Ni, in particular context alkene functionalization.Alkenes are versatile functional groups, but stereoselective carbofunctionalization reactions alkenes have been underdeveloped. This challenge may derive difficulty controlling selectivity via traditional two-electron migratory insertion pathways. could lead different stereodetermining steps mechanisms, allowing molecular scaffolds that otherwise difficult prepare. For example, an asymmetric diarylation reaction developed by our relies upon Ni(III) intermediates control enantioselectivity give library chiral α,α,β-triarylethane molecules with biological activity.Mechanistic studies on two-component reductive 1,2-difunctionalization shed light origin cross-electrophile selectivity, as C sp2 sp3 electrophiles independently activated at Ni(I) respectively. Catalyst reduction has identified be turnover-limiting step this system. A closer investigation formation using (Xantphos)Ni(I)Ar model complex reveals initiates concerted halogen-abstraction pathway.The potentials allowed us develop reductive, trans-selective diene cyclization, wherein classic mechanism operates Ni(I)/Ni(III) platform, accounting for chemo- stereoselectivity. found applications efficient synthesis pharmaceutically relevant molecules, such 3,4-dimethylgababutin.The tendency one-electron processes prompted explore dinuclear Ni-mediated bond formations. provide insight into Ni–Ni bonding two metal centers react cooperatively promote C–C, C–X, N–N forming elimination.Finally, isolation β-agostic Pd X-ray neutron diffraction characterization highly reactive molecules. The parameters serve unambiguous evidence interactions help rationalize slower elimination relative Pd. Overall, elucidated several contexts. Greater mechanistic understanding facilitates catalyst design helps reactivity Ni-catalyzed functionalization reactions.

Язык: Английский

---

Cross-Electrophile Couplings of Activated and Sterically Hindered Halides and Alcohol Derivatives

Accounts of Chemical Research, Год журнала: 2020, Номер 53(9), С. 1833 - 1845

Опубликована: Авг. 25, 2020

ConspectusTransition metal catalyzed cross-electrophile coupling of alkyl electrophiles has evolved into a privileged strategy that permits the facile construction valuable C(sp3)–C bonds. Numerous elegant Ni-catalyzed methods, for example, arylation, allylation, acylation, and vinylation primary secondary halides have been developed. This prior work provided important mechanistic insights selectivity reactivity partners, which are largely dictated by both catalysts reactants. In spite advances made to date, number challenging issues remain, including (1) achieving stereoselective syntheses C–C bonds rely primarily on functionalized or activated precursors, (2) diversifying electrophiles, (3) gaining underlying reaction mechanisms.In this Account, we summarize Ni- Fe-catalyzed reductive bond forming methods developed in our laboratory, allowed us couple activated, sterically hindered tertiary C(sp3)–O access methylated trifluoromethylated products, esters, C-glycosides, quaternary carbon centers. We will begin with brief discussion chemoselective unactivated alkyl–alkyl bonds, focus effects ligands reductants, along leaving group-directed reactivities halides, role they play promoting methyl, trifluoromethyl, glycosyl chloroformates. Matching these suitable partners is considered essential success; something can be tuned means appropriate Ni catalysts. Second, detail how tuning steric electronic nickel labile pyridine-type additives (primarily MgCl2) effective creation arylated all-carbon centers through aryl encumbered halides. contrast, use bulkier bipyridine terpyridine incorporation relative small-sized acyl allyl groups acylated allylated Finally, show knowledge gained halide enabled develop permit oxalates allyl, aryl, vinyl wherein Barton C–O radical fragmentation mediated Zn MgCl2 promoted The same protocol applicable arylation derived from α-hydroxyl carbonyl substrates, involves formation relatively stable α-carbonyl centered radicals. Thus, Account not only summarizes synthetic allow using but also provides insight relationship between structure substrates catalysts, as well additives.

Язык: Английский

---

Enantioselective Three-Component Fluoroalkylarylation of Unactivated Olefins through Nickel-Catalyzed Cross-Electrophile Coupling

Journal of the American Chemical Society, Год журнала: 2020, Номер 142(21), С. 9604 - 9611

Опубликована: Май 11, 2020

A nickel-catalyzed, enantioselective, three-component fluoroalkylarylation of unactivated alkenes with aryl halides and perfluoroalkyl iodides has been described. This cross-electrophile coupling protocol utilizes a chiral nickel/BiOx system as well pendant chelating group to facilitate the challenging three-component, asymmetric difunctionalization alkenes, providing direct access valuable β-fluoroalkyl arylalkanes high efficiency excellent enantioselectivity. The mild conditions allow for broad substrate scope good functional toleration.

Язык: Английский

---

Asymmetric Ni-Catalyzed Radical Relayed Reductive Coupling

Journal of the American Chemical Society, Год журнала: 2020, Номер 142(31), С. 13515 - 13522

Опубликована: Июнь 29, 2020

Alkene dicarbofunctionalizations enable the streamlined construction of aliphatic structures and have thus been subject intense research efforts. Despite significant progress, catalytic asymmetric variants remain scarce. Inspired by advantages reductive cross-coupling approaches, we present here a highly efficient intermolecular Ni-catalyzed dicarbofunctionalization alkenes. Two distinct readily available electrophiles, namely, Csp2- Csp3-halides, are added simultaneously across variety olefins (vinyl amides, vinyl boranes, phosphonates) at room temperature in regio- enantioselective manner. The reaction, devoid sensitive organometallic reagents, takes advantage an situ generated chiral alkyl Ni(III)-intermediate to ensure stereodefined outcome Csp3–Csp2 bond-forming reaction. An (l)-(+)-isoleucine bisoxazoline ligand presence coordinating sites on alkene key for successful these "asymmetric radical relayed couplings" (ARRRCs). Further, multiple transformations amides obtained this process showcase potential new methodology straightforward assembly building blocks such as primary secondary amines oxazolines, highlighting its synthetic utility.

Язык: Английский

---

Mechanism of Ni-Catalyzed Reductive 1,2-Dicarbofunctionalization of Alkenes

Journal of the American Chemical Society, Год журнала: 2019, Номер 141(44), С. 17937 - 17948

Опубликована: Окт. 7, 2019

Ni-catalyzed cross-electrophile coupling reactions have emerged as appealing methods to construct organic molecules without the use of stoichiometric organometallic reagents. The mechanisms are complex: plausible pathways, such "radical chain" and "sequential reduction" mechanisms, dependent on sequence activation electrophiles. A combination kinetic, spectroscopic, studies reveals that a Ni-catalyzed, reductive 1,2-dicarbofunctionalization alkenes proceeds through pathway. reduction Ni by Zn is turnover-limiting step, consistent with Ni(II) intermediates catalyst resting-state. only sufficient reduce (phen)Ni(II) Ni(I) species. As result, commonly proposed Ni(0) absent under these conditions. (Phen)Ni(I)–Br selectively activates aryl bromides via two-electron oxidation addition, whereas alkyl activated (phen)Ni(I)–Ar single-electron afford radicals. These findings could provide insight into achieving selectivity between different

Язык: Английский

---

Ni-Catalyzed Reductive Dicarbofunctionalization of Nonactivated Alkenes: Scope and Mechanistic Insights

Journal of the American Chemical Society, Год журнала: 2019, Номер 141(35), С. 13812 - 13821

Опубликована: Авг. 21, 2019

Olefins devoid of directing or activating groups have been dicarbofunctionalized here with two electrophilic carbon sources under reductive conditions. Simultaneous formation one C(sp3)–C(sp3) and C(sp3)–C(sp2) bond across a variety unbiased π-systems proceeds exquisite selectivity by the combination Ni catalyst TDAE as sacrificial reductant. Control experiments computational studies revealed feasibility radical-based mechanism involving, formally, interconnected Ni(I)/Ni(III) processes demonstrated different ability Ni(I) species (Ni(I)I vs PhNi(I)) to reduce C(sp3)–I bond. The role reductant was also investigated in depth, suggesting that one-electron reduction Ni(II) is thermodynamically favored. Further, preferential activation alkyl aryl halides ArNi(I) complexes well high affinity ArNi(II) for secondary over tertiary C-centered radicals explains lack undesired homo- direct coupling products (Ar–Ar, Ar–Alk) these transformations.

Язык: Английский

---

A Radical Approach to Anionic Chemistry: Synthesis of Ketones, Alcohols, and Amines

Journal of the American Chemical Society, Год журнала: 2019, Номер 141(16), С. 6726 - 6739

Опубликована: Апрель 3, 2019

Historically accessed through two-electron, anionic chemistry, ketones, alcohols, and amines are of foundational importance to the practice organic synthesis. After placing this work in proper historical context, Article reports development, full scope, a mechanistic picture for strikingly different way forging such functional groups. Thus, carboxylic acids, once converted redox-active esters (RAEs), can be utilized as formally nucleophilic coupling partners with other derivatives (to produce ketones), imines benzylic amines), or aldehydes alcohols). The reactions uniformly mild, operationally simple, and, case ketone synthesis, broad scope (including several applications simplification synthetic problems parallel synthesis). Finally, an extensive study synthesis is performed trace elementary steps catalytic cycle provide end-user clear understandable rationale selectivity, role additives, underlying driving forces involved.

Язык: Английский

---

Nickel‐CatalyzedDicarbofunctionalization of Alkenes^†

Chinese Journal of Chemistry, Год журнала: 2020, Номер 38(11), С. 1371 - 1394

Опубликована: Июнь 16, 2020

As a straightforward strategy for rapidly increasing molecular complexity, dicarbofunctionalization of alkenes has attracted substantial interests organic synthesis, medicine chemistry, and materials science. Nickel‐catalyzed cascade dicarbofunctionalizations have been flourished in this area recently, nickel‐mediated radical pathways particularly offer new opportunities conjunctive cross‐couplings with alkyl coupling partners. Herein, we give comprehensive review nickel‐catalyzed through historical perspective, including intermolecular three‐component reactions intramolecular reactions. Among the discussed review, carbometallation/cross‐coupling process addition/cross‐coupling are two major alkenes. The oxidative cyclization 1,2‐metallate shift processes also selectively discussed. These methods overcome limitations associated using noble metals field, providing an efficient access to structurally diversified molecules.

Язык: Английский

---