Ni/Co-Catalyzed Homo-Coupling of Alkyl Tosylates

Komeyama, Kimihiro; Tsunemitsu, Ryusuke; Yoshida, Hiroto; Osaka, Itaru

doi:10.3390/molecules24081458

Cited by 18 publications

(8 citation statements)

References 52 publications

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“…Very recently, Komeyama and coworkers extended the Ni/Co‐catalyst system mentioned above to the C(sp 3 )−C(sp 3 ) homocoupling of alkyl tosylates (Scheme ) and the cross‐coupling between alkyl halides and alkyl tosylates (Scheme ) . The homocoupling provided essential insights into the understanding of the mechanism of the Ni/Co‐catalyzed coupling.…”

Section: Planar Co(i) Complexesmentioning

confidence: 99%

Recent Advances in Four‐Coordinated Planar Cobalt Catalysis in Organic Synthesis

Komeyama

2019

Asian J Org Chem

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In the field of transition metal‐catalyzed organic transformations, four‐coordinated planar cobalt complexes represent an active area of research due to their low cost, abundance on earth, and unique catalytic activity based on the three oxidation states of cobalt. These complexes can behave as various reactive intermediates, such as Co(II) metalloradicals, Co(III) hydrides, Co(I) bases, and Co(I) nucleophiles, according to the ligand field theory. For instance, planar Co(II) species have a d7 electronic configuration and act as metalloradical catalysts, which react with diazo and azide compounds to form reactive intermediates such as Co(III) carbene‐radicals and Co(III) nitrene‐radicals, respectively. These intermediates enable efficient cyclopropanation and aziridination of alkenes and C(sp3)‐H bond functionalization. Furthermore, the hydrogen bonding interaction between amide groups of planar ligands and polar substituents of the carbon radical on the Co(III) carbene‐radicals not only creates robust chiral cavities but also contributes to the stabilization of the Co(III) carbene‐radical and the transition state, consequently resulting in a dramatic improvement in reaction efficiency. The Co(III)‐hydrides provide a useful method for the generation of carbon radicals through hydrocobaltation of alkenes followed by homolytic cleavage of the Co−C bond. The carbon radical formation can participate in various hydrofunctionalizations and alkene‐isomerization. The d8 planar Co(I) complexes act as a base because they have an electronically filled dz2 orbital as the highest occupied molecular orbital (HOMO). This basicity enables various aromatic C−H functionalizations without a stoichiometric amount of oxidant. In contrast, the same planar Co(I) also acts as a superior nucleophilic catalyst, which can react with carbon electrophiles such as epoxides and organic (pseudo)halides to produce the corresponding alkyl‐Co(III) species. The generated alkyl‐Co(III) can be converted into the carbon radical or undergo transalkylation reaction with other transition metal catalysts. The strategies provide a new method for organic transformation with carbon electrophiles. This minireview covers recent developments in the field of four‐coordinated planar cobalt‐catalyzed organic transformations, paying particular attention to the relationship between their catalytic activities and oxidation states. The reactions have been categorized into those involving planar Co(II) complexes, Co(III) hydrides, and Co(I) complexes, with representative examples and insightful mechanistic discussions.

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Section: Planar Co(i) Complexesmentioning

confidence: 99%

Recent Advances in Four‐Coordinated Planar Cobalt Catalysis in Organic Synthesis

Komeyama

2019

Asian J Org Chem

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“…Alkyl sulfonates have a history of use in nickel-catalyzed cross-coupling (XC) and XEC reactions. − Notably, sulfonates utilized in these reactions are frequently generated in situ from the corresponding alcohols. In the context of cross-coupling reactions, nickel-catalyzed Negishi couplings of benzylic mesylates and Kumada reactions of cyclic sulfates have been reported (Scheme a). , The use of alkyl sulfonates as electrophiles in nickel-catalyzed XEC reactions developed contemporaneously, beginning with homocoupling reactions . Chemoselective XEC reactions have utilized alkyl sulfonates with aryl and vinyl halides and pseudohalides (Scheme b). − Cross-selective pairing of two alkyl electrophiles was demonstrated using methyl tosylate (Scheme c). , However, to the best of our knowledge, no cross-selective XEC reaction of two primary or secondary alkyl sulfonates has been reported.…”

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confidence: 99%

Nickel-Catalyzed Alkyl–Alkyl Cross-Electrophile Coupling Reaction of 1,3-Dimesylates for the Synthesis of Alkylcyclopropanes

et al. 2020

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Cross-electrophile coupling reactions of two Csp3–X bonds remain challenging. Herein we report an intramolecular nickel-catalyzed cross-electrophile coupling reaction of 1,3-diol derivatives. Notably, this transformation is utilized to synthesize a range of mono- and 1,2-disubstituted alkylcyclopropanes, including those derived from terpenes, steroids, and aldol products. Additionally, enantioenriched cyclopropanes are synthesized from the products of proline-catalyzed and Evans aldol reactions. A procedure for direct transformation of 1,3-diols to cyclopropanes is also described. Calculations and experimental data are consistent with a nickel-catalyzed mechanism that begins with stereoablative oxidative addition at the secondary center.

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“…According to the literature, the interception of alkyl radicals generated in the Co-catalytic cycle with Ni-species, either before or after the oxidative addition, leads to the formation of a C-C bond. [15][16][17][18][19][20][21] We hypothesize that radicals formed from oxetanes would follow this pathway. To this end, our experimental investigations began with the conditions adopted from those developed for epoxides.…”

Section: Resultsmentioning

confidence: 99%

Radical Ring-Opening of Oxetanes Enabled by Co-Catalysis

Potrząsaj¹,

Ociepa²,

Chaładaj³

et al. 2021

Preprint

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Oxetanes are valuable building blocks due to their well-explored propensity to undergo ring-opening reactions with diverse nucleophiles. However, their application as precursors of radical species remains unexplored. Herein, we present a cobalt catalysis-based strategy to access various modes of radical reactivity via oxetane ring opening. The developed method involves formation of an alkylated Co-complex intermediate from vitamin B12 and oxetane. Homolytic cleavage of the Co-C bond generates nucleophilic radicals that engage in reactions with SOMOphiles and low-valent transition metals. The scope of the developed reactions is broad with various functional groups being well tolerated. Importantly, the regioselectivity of these processes complements known methodologies.

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Ni/Co-Catalyzed Homo-Coupling of Alkyl Tosylates

Cited by 18 publications

References 52 publications

Recent Advances in Four‐Coordinated Planar Cobalt Catalysis in Organic Synthesis

Recent Advances in Four‐Coordinated Planar Cobalt Catalysis in Organic Synthesis

Nickel-Catalyzed Alkyl–Alkyl Cross-Electrophile Coupling Reaction of 1,3-Dimesylates for the Synthesis of Alkylcyclopropanes

Radical Ring-Opening of Oxetanes Enabled by Co-Catalysis

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