Nickel-catalyzed C-O/N-H, C-S/N-H, and C-CN/N-H annulation of aromatic amides with alkynes: C-O, C-S, and C-CN activation

Synthesis of 3,4-unsubstituted isoquinolone derivatives from benzimidates and vinylene carbonate via cobalt(III)-catalyzed C-H activation/cyclization

A cobalt(III)-catalyzed C-H activation/cyclization of benzimidates and vinylene carbonate has been developed. Various benzimidates showed good compatibility, providing isoquinolone derivatives in moderate to good yields. This strategy employs the inexpensive Co(III) as the catalyst and provides an efficient and practical solution for the synthesis of medicinally valuable 3,4-unsubstituted isoquinolone derivatives.

Platform for the Immobilizing of Ultrasmall Pd Clusters for Carbonylation: In Situ Self-Templating Fabrication of ZIF-8 on ZnO

Incorporating metal clusters into the confined cavities of metal-organic frameworks (MOFs) to form MOF-supported catalysts has attracted considerable research interest with regard to carbonylation reactions. Herein, a self-templating method is used to prepare the zinc oxide (ZnO)-supported core-shell catalyst ZnO@Pd/ZIF-8. This facile strategy controls the growth of metal sources on the ZIF-8 shell layer and avoids the metal diffusion or aggregation problems of the conventional synthesis method. The characteristics of the catalysts show that the palladium (Pd) clusters are highly dispersed with an average particle size of ≈1.2 nm, making them excellent candidates as a catalyst for carbonylation under mild conditions. The optimal catalyst (1.25-ZnO@Pd/ZIF-8) exhibits excellent activity in synthesizing α, β-alkynyl ketones under 1 atm of carbon monooxide (CO), and the conversion rate of 1, 3-diphenylprop-2-yn-1-one is 3.09 and 3.87 times more than those of Pd/ZIF-8 and Pd2+, respectively, for the first 2 h. Moreover, the 1.25-ZnO@Pd/ZIF-8 is recyclable, showing negligible metal leaching, and, under the conditions used in this investigation, can be reused at least five times without considerable loss in its catalytic efficiency. This protocol can also be applied with other nucleophile reagents to synthesize esters, amides, and acid products.

Sulfur in Waste-Free Sustainable Synthesis: Advancing Carbon-Carbon Coupling Techniques

This review explores the pivotal role of sulfur in advancing sustainable carbon-carbon (C-C) coupling reactions. The unique electronic properties of sulfur, as a soft Lewis base with significant mesomeric effect make it an excellent candidate for initiating radical transformations, directing C-H-activation, and facilitating cycloaddition and C-S bond dissociation reactions. These attributes are crucial for developing waste-free methodologies in green chemistry. Our mini-review is focused on existing sulfur-directed C-C coupling techniques, emphasizing their sustainability and comparing state-of-the-art methods with traditional approaches. The review highlights the importance of this research in addressing current challenges in organic synthesis and catalysis. The innovative use of sulfur in photocatalytic, electrochemical and metal-catalyzed processes not only exemplifies significant advancements in the field but also opens new avenues for environmentally friendly chemical processes. By focusing on atom economy and waste minimization, the analysis provides broad appeal and potential for future developments in sustainable organic chemistry.

Computational Exploration of 1,2-Carboamine Carbonylation Catalyzed by Nickel

Nickel-catalyzed carbonylation of alkenes is a stereoselective and regioselective method for the synthesis of amide compounds. Theoretical predictions with density functional theory calculations revealed the mechanism and origin of stereoselectivity and regioselectivity for the nickel-catalyzed carbonylation of norbornene. The carbonylation reaction proceeds through oxidative addition, migration insertion of alkenes, and subsequent reduction elimination to afford cis-carbonylation product. The C-N bond activation of amides is unfavorable because the oxidative addition ability of the C-C bond is stronger than that of the C-N bond. The determining step of stereoselectivity is the migratory insertion of the strained olefin. The structural analysis shows that steroselectivity is controlled by the steric hindrance of methyl groups to olefins and substituents to IMes in ligands.

Access to N-Aryl (Iso)quinolones via Aryne-Induced Three-Component Coupling Reaction

N-Aryl (iso)quinolones are of increasing interest in material and medicinal chemistry, although general routes for their provision remain underexplored, especially when compared with its N-alkyl counterparts. Herein, we report a modular and transition-metal-free, aryne-induced three-component coupling protocol that allows the facile synthesis of structurally diverse N-aryl (iso)quinolones from readily accessible halo-(iso)quinolines in the presence of water. Preliminary results highlight the applicability of our method through scale-up synthesis, downstream derivatization, and flexible synthesis involving other types of aryne precursors.

Nickel-Catalyzed Intramolecular Dual Annulation Reaction of Aryl Nitrile-Containing 1,2,3-Benzotriazin-4(3H)-ones: A Pathway To Synthesize Luotonin A and Related Polycyclic Pyrroloquinazolinones

Herein, we report a nickel-catalyzed intramolecular denitrogenative dual annulation reaction of aryl nitrile-containing 1,2,3-benzotriazine-4(3H)-ones to synthesize polycyclic pyrroloquinazolinones with a tolerance of a wide diversity of substituents. This catalytic reaction is the first denitrogenative transannulation of 1,2,3-benzotriazine-4(3H)-one with nitrile, which can be applied as the critical step to synthesize luotonin A with a high step economy.

Nickel-Catalyzed Functionalization Reactions Involving C-H Bond Activation via an Amidate-Promoted Strategy and Its Extension to the Activation of C-F, C-O, C-S, and C-CN Bonds

ConspectusThe development of functionalization reactions involving the activation of C-H bonds has evolved extensively due to the atom and step economy associated with such reactions. Among these reactions, chelation assistance has been shown to provide a powerful solution to the serious issues of reactivity and regioselectivity faced in the activation of C-H bonds. The vast majority of C-H functionalization reactions reported thus far has involved the use of precious metals. Kleiman and Dubeck reported the cyclonickelation of azobenzene and NiCp2 in which an azo group directs a Ni center to activate the ortho C-H bond in close proximity. Although this stoichiometric reaction was discovered earlier than that for other transition-metal complexes, its development as a catalytic reaction was delayed. No general catalytic systems were available for Ni-catalyzed C-H functionalization reactions for a long time. This Account details our group's development of Ni(0)- and Ni(II)-catalyzed chelation-assisted C-H functionalization reactions. It also highlights how the new strategy can be extended to the activation of other unreactive bonds.In the early 2010s, we found that the Ni(0)-catalyzed reaction of aromatic amides that contain a 2-pyridinylmethylamine moiety as a directing group with alkynes results in C-H/N-H oxidative annulation to give isoquinolinones. In addition, the combination of a Ni(II) catalyst and an 8-aminoquinoline directing group was found to be a superior combination for developing a wide variety of C-H functionalization reactions with various electrophiles. The reactions were proposed to include the formation of unstable Ni(IV) and/or Ni(III) species; the generation of such high-valence Ni species was rare at that time, but since then, many papers dealing with DFT and organometallic studies have appeared in the literature in attempts to understand the mechanism. Based on our in-depth considerations of the mechanism with respect to why an N,N-bidentate directing group is required, we realized that the formation of a N-Ni bond by the oxidative addition of a N-H bond to a Ni(0) species or a ligand exchange between a N-H bond and Ni(II) species is the key step. We concluded that the precoordination of the N(sp2) atom in the directing group positions the Ni species to be in close proximity to the N-H bond which permits the formation of a N-Ni bond. Based on this working hypothesis, we carried out the reaction using KOtBu as a base and found that the Ni(0)-catalyzed reaction of aromatic amides that do not contain such a specific directing group with alkynes results in the formation of the desired isoquinolinone, in which an amidate anion acts as the actual directing group. Remarkably, this strategy was found to be applicable to the activation of various other unreactive bonds such as C-F, C-O, C-S, and C-CN.

Rh(III)-Catalyzed Dual C-H Functionalization and C-O/C-N Annulations of Monoamide Fumarates

Pyrano[4,3-c]pyridine-diones, which are the key skeleton of bioactive compounds and functional materials, are usually prepared via a multistep synthesis using expensive substrates. This work demonstrates that Rh(III)-catalyzed dual C(sp²)-H functionalization and C-O/C-N annulation of monoamide fumarates can produce pyrano[4,3-c]pyridine-1,5(6H)-diones in high yield (up to 82%) in a single step. The substrates of monoamide fumarates and acetylenes are structurally simple, readily available, and inexpensive. The additive AgSbF₆ effectively raised the yields. On account of easier dehydrogenation of OH in the COOH group than NH in the amide group in the reaction, the process first undergoes C-O annulation and then is succeeded by C-N annulation.

Selective Nickel-Catalyzed Hydrodefluorination of Amides Using Sodium Borohydride

Hydrodefluorination selective to the ortho position to amides is accomplished under mild conditions using sodium borohydride and a nickel catalyst. The facile formation of a nickelacycle intermediate with a specific geometry ensures selectivity without the need for electronic directing groups, and fluorine atoms in other positions remain intact. This method avoids the use of stoichiometric silanes which are typical for most other defluorination reactions, resulting in virtually no organic waste byproducts.

Nickel‐Catalyzed C sp2 −OMe Functionalization for Chemoselective Aromatic Homologation En Route to Nanographenes

A Ni‐catalyzed C_sp2−OMe ortho‐functionalization methodology to form chemoselectively alkyne monoannulation or aromatic homologation products is reported as a novel protocol towards the valorisation of substrates containing C_sp2−OMe units. Double activation of C_sp2−OMe and C_sp2−F bonds is also demonstrated. Further use of aromatic homologation products towards the synthesis of nanographene‐like compounds is described.

Cobalt-Catalyzed Cyclization of 2-Bromobenzamides with Carbodiimides: A New Route for the Synthesis of 3-(Imino)isoindolin-1-ones

A novel synthetic pathway to approach 3-(imino)isoindolin-1-ones by the Co-catalyzed cyclization reaction of 2-bromobenzamides with carbodiimides has been developed. This catalytic reaction can tolerate a variety of substituents and provide corresponding products in moderate yields for most cases. According to the literature, the reaction mechanism is proposed through the formation of a five-membered aza-cobalacycle complex, which carries out the following reaction subsequence, including nucleophilic addition and substitution, to furnish the desired structures.

Nickel-catalyzed Suzuki–Miyaura cross-coupling of C–F bonds

The efficient Suzuki–Miyaura cross-coupling of ortho-fluoro aromatic amides with aryl boronates is described. The reaction proceeds effectively, even at 60 °C. The reaction exhibits a good tolerance for functional groups and a broad scope for aromatic amides.

Cobalt-catalyzed coupling reactions of 2-halobenzamides with alkynes: investigation of ligand-controlled dual pathways

The Co-catalyzed reactions of 2-halobenzamides and alkynes to form quinolinones or 2-vinyl benzamides are described here. These two reactions can be controlled merely by ligands.

Facile construction of peptidomimetics by sequential C–S/C–N bond activation of Ugi-adducts

Diverse peptidomimetics containing a primary amide are prepared via the integration of an Ugi-4CR and sequential C–S/C–N bond activation.

Nickel-Catalyzed C–F/N–H Annulation of 2-(2-Fluoroaryl) N-Heteroaromatic Compounds with Alkynes: Activation of C–F Bonds

The reaction of 2-(2-fluoroaryl) N-heteroaromatic compounds, such as benzimidazole and indole derivatives, with internal alkynes in the presence of a catalytic amount of a nickel complex results in C–F/N–H annulation with alkynes. The reaction shows a high functional group compatibility. The presence of a strong base, such as KOBu­ t or LiOBu t , is required for the reaction to proceed.