Cobalt-Catalyzed Cross-Coupling Reactions Abdol R. Hajipour

High catalytic activity Vitamin B12 Cobalt Readily available Non-toxic Low-cost Stable in air High catalytic activity

These reactions are believed to proceed by an uncommon mechanism involving a carbon-centered radical species. Cobalt complexes can also be used to effect cascade transformations in which radical cyclization is followed by subsequent cross-coupling. Cobalt-Catalyzed Dimerization of Grignard Reagents

Oshima proposed mechanism

Hoffman proposed mechanism

Scope pf aryl halides in cobalt-catalyzed cross-coupling reaction

Proposed mechanism of cobalt-catalyzed radical cyclization/cross-coupling reaction

Scope of tandem cyclization/cross-coupling

Organozinc compounds Carbonylation of diorganozinc species using cobalt catalysis

e Synthesis of functionalized arylzinc reagents and their consecutive reaction with acid chlorides Proposed mechanism for the acylation of aryl zinc species with acyl chloride using cobalt catalyst

One-step synthesis of aromatic ketones from functionalized aryl bromides and acid anhydrides Cobalt-catalyzed alkenylation of zinc organometallics

Cbalt-catalyzed cross-coupling between aryl zinc species and activated olefins

Cobalt-catalyzed allylation of diarylzinc reagents with allyl chloride Cobalt-catalyzed allylation of diarylzinc reagents with allyl acetate

Organocopper Cobalt-catalyzed cross-coupling between aryl halides and arylcopper compounds

General procedure for the cobalt-catalyzed vinylation of functionalized aryl halides with vinyl acetates Cobalt-catatyzed electrochemical vinylation of aryl halides using vinyl acetates

Proposed mechanism for the vinylation of aryl halides with vinyl acetates

Cobalt-catalyzed direct electrochemical cross-coupling between aryl halides and allylic acetate Coupling reaction between aromatics chloride and allyl acetate

Cross-coupling reaction between heteroaromatic halides and allyl methacrylates Mechanism of the cobalt-catalyzed electrochemical coupling between aromatic halides and allylic acetates

Aryl chlorides allylation by allyl acetate with Co-Fe-Mn

Electroreductive cobalt-catalyzed cross-coupling of aryl halides Cobalt-catalyzed electrochemical cross-coupling of functionalized phenyl halides with 4-chloroquinoline derivatives

Proposed mechanism for the cobalt-catalyzed formation of biaryls

Cobalt-Catalyzed C−H Arylations, Benzylations, and Alkylations with Organic Electrophiles and Beyond Cobalt-mediated direct functionalized of azobenzene

Cobalt-catalyzed C-H arylation with aryl sulfamates

Cobalt-catalyzed C-H arylations with carbamates

C-H arylation of aromatic imines 10 with aryl chloride 11

The mechanism of C-H arylation

C-H alkylation of ketamines

C-H activation reactions N0 # 1 In our laboratory C-H activation reactions N0 # 1 Cobalt-Catalyzed C-H Activation/C-O Formation: Synthesis of Benzofuranones

Effect of reaction parameters in synthesis of benzofuranones.a) Entry Cobalt salt ligand RMgBr Yield [%]b) 1 CoBr2 IMes•HCl iPrMgBr 52   2 IPr•HCl 48c) 3 SIMes•HCl 57 4 PPh3 64 5 4-OMe-PhMgBr 35c) 6 4-NO2-PhMgBr 7 tBuCH2MgBr 49 8 CoSO4 16c) 9 Co(NO3)2 10 CoCl2 87

Plausible catalytic cycle for the cobalt- catalyzed C−H lactonization

No # 2 Cobalt-Catalyzed Intramolecular Arylation of 2-Bromo-Aromatic imine via Directed C–H Bond Functionalization: Synthesis of Phenanthridinr Skeleton

Scope of Varieties of Acetophenone-derived

Plausible Catalytic Cycle for the Cobalt-Catalyzed C−H Functionalizations

Nanocatalyst More surface area Eliminating the undesired products Controllable size and morphology More selectivity and activity High diversity and capability of chemical modification Recoverable Aggregation possibility

Cross-coupling reaction No # 1 Application of Co- and CoFe2O4-NPs in C–N and C–O bond formation: benzimidazole and benzoxazole synthesis Catalyst preparation: 10 mL Hydrazine NaOH 60% efficient methods for the synthesis of substituted benzimidazoles and benzoxazoles using green and inexpensive cobalt catalysts under ligand-free conditions have been developed. Two different catalysts ofmagnetic and pure cobalt were synthesized and their activities in intramolecular C–O and C–N bond formation reactions were compared. These nanoparticles are easily made, air-stable, low-cost and efficient. Both of the catalysts can be recovered and reused without remarkable loss of activity. A comparison of these two catalytic systems showed that their activities are close to each other; however, the reactions catalyzed by the cobalt nanoparticles were complete in relatively shorter reaction times compared to the cobalt ferrite ones.

Catalyst characterization:

No # 2 Cobalt nanoparticles supported on ionic liquid functionalized-multiwall carbon nanotubes as an efficient and recyclable catalyst for Heck reaction we have prepared Co NPs immobilized on imidazolium ionic liquid-functionalized MWCNTs (Co-IL MWCNT) which can be used as an environmentally friendly and economical catalyst for the Heck coupling reaction. This coupling reaction can proceed without the need for an expensive palladium catalyst and toxic ligands in a markedly short reaction time.

Catalyst Characterization FT-IR TEM

No # 3 Multi walled carbon nanotubes supported N-heterocyclic carbene cobalt (ΙΙ) as a novel, efficient and inexpensive catalyst for the Mizoroki–Heck reaction cobalt supported on direct functionalization MWCNTs as NHC precursor was fabricated for the first time. The prepared Co–NHC@MWCNT catalyst exhibited high catalytic activity for the Mizoroki–Heck reaction. The current strategy is a novel, environmentally friendly and economical way for the Heck reaction using significantly low cobalt loading. It could be recycled and reused six times without obvious cobalt leaching.

Catalyst preparation:

Catalyst Characterization FT-IR

TEM ICP analysis 0.35 mmol/g (Co / catalyst) CHN analysis N % C % H % Ligand loading (%) Theoretical 13.99 79.97 6.04 4/25 mmol/g Experimental 1.2 12.1 2.1 ICP analysis 0.35 mmol/g (Co / catalyst)

No # 4 Pd/Cu-free Heck and Sonogashira cross-coupling reaction by Co nanoparticles immobilized on magnetic chitosan as reusable catalyst this study highlights the multifaceted advantages of CS as a sustainable material for the textural engineering of macroporous supports, whereas chemical modification of its amino groups with safe and green organic compounds, such as methyl salicylate, allows the tuning of the metal support interaction. Mild and sustainable reaction conditions (palladium and copper-free, polyethylene glycol as solvent, 80 °C) enables Heck cross-coupling catalysis to be performed in good yields with low metal contamination, and easy and good recyclability. This straightforward and sustainable chemistry affords useful and eco-efficient catalysts with many useful properties including their green and easy conditions to produce the catalyst (without using toxic agents and solvent) and good efficiencies for the Heck and Sonogashira coupling reactions. In general, this study presents the first example of the application of the functionalization of magnetic chitosan with methyl salicylate to prepare a stable heterogeneous cobalt complex. The requirements of energy and time for the Heck reaction are extremely minimized in this method compared to the previously report cobalt-catalyzed Heck cross coupling reactions as an inevitable trend in development of green chemistry. Moreover, it is the first report of applying a cobalt catalyst in the Sonogashira reaction.

SEM-EDX TEM

Comparison of catalytic activities of our catalystS with rare literature examples for Heck reaction between iodobenzene and methyl acrylate Entry Catalyst Reaction conditions Time (h) Yield (%) 1 Nano Co Co (2 mol%) in NMP at 130 ºC 14 78 2 Co/Al2O3 Co (10 mol%) in NMP at 150 ºC 24 56 3 Co (2 mol%) in NMP at 140 ºC 16 85 4 Co-B Co (5 mol %) in water/DMF (5/5) at 130 ºC 12 98 5 Co-IL@MWCNTs Co (5 mol %) in toluene at 100 ºC 87 6 Co–NHC@MWCNTs Co (3.5 mol %) in PEG at 80 ºC 7 MNPs@/Cs-MS-Co Co (1.1 mol %) in PEG at 80 ºC 88 Note: Further applications of cobalt catalytic system in coupling reactions are under investigation in our laboratory.

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