Co(III)−Alkyl Complex- and Co(III)−Alkylperoxo Complex-Catalyzed Triethylsilylperoxidation of Alkenes with Molecular Oxygen and Triethylsilane

Tokuyasu, Takahiro; Kunikawa, Shigeki; Masuyama, and Araki; Nojima, Màsatomo

doi:10.1021/ol0201299

Cited by 121 publications

(116 citation statements)

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“…Some mechanistic insights into this peroxygenation reaction were gleaned by Isayama and Nojima . They observed the occurrence of an induction period in the Co(II)‐catalyzed peroxygenation, which was significantly shortened by the addition of a small amount of tert ‐butyl hydroperoxide ( t BuOOH).…”

Section: Planar Co(iii)‐hydride Complexesmentioning

confidence: 99%

“…[40] Some mechanistic insights into this peroxygenation reaction were gleaned by Isayama [40b] and Nojima. [41] They observed the occurrence of an induction period in the Co(II)-catalyzed peroxygenation, which was significantly shortened by the addition of a small amount of tert-butyl hydroperoxide ( t BuOOH). This result strongly suggests that the addition of the peroxide accelerates the formation of Co(III)-alkoxides 45 or Co (III)-alkyl peroxides 46, thereby enabling a rapid metal-exchange with hydrosilane to give active Co(III)-hydride complexes 47 (Scheme 23).…”

Section: Planar Co(iii)-hydride Complexesmentioning

confidence: 99%

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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(iii)‐hydride Complexesmentioning

confidence: 99%

Section: Planar Co(iii)-hydride Complexesmentioning

confidence: 99%

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

Komeyama

2019

Asian J Org Chem

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“…20 Trioxepanes 3a and 3b were prepared via parallel routes (Scheme 3) beginning with alcohol 13 21 and cinnamyl alcohol (14). The corresponding acetates (15, 16) underwent successive Co-mediated dioxygenation 22 and chemoselective reduction to furnish triethylsilyl peroxyalcohols 17 and 18. 23 The peroxyalcohols underwent HF-mediated condensation with ketone 5 to produce 3a and 3b.…”

mentioning

confidence: 99%

Spiroadamantyl 1,2,4-trioxolane, 1,2,4-trioxane, and 1,2,4-trioxepane pairs: Relationship between peroxide bond iron(II) reactivity, heme alkylation efficiency, and antimalarial activity

Wang

Creek

Schiaffo

et al. 2009

Bioorganic & Medicinal Chemistry Letters

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“…Although some examples of cobalt hydrides with nonporphyrinoid ligands have been characterized [49][50][51][52], mechanistic studies involving finetuning of reductive catalytic activity of cobalt porphyrinoids have encountered difficulties because of the inaccessibility of the key reactive intermediate, a cobalthydride (Co-H) species. In this context, the porphycene ligand is expected to provide us with the ability to characterize the porphyrinoid Co-H species because the lower ligand symmetry of the porphycene ring makes the low LUMO energy level available and the ligand character is expected to stabilize the hydride species.…”

Section: Introductionmentioning

confidence: 99%

Reaction of cobalt porphycene with hydride reagents: spectroscopic detection of Co–H porphycene species and formation of Co–SnR₃ porphycene species

Matsuo

Komatsuzaki

Tsuji

et al. 2012

J. Porphyrins Phthalocyanines

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The reaction of tetrapropylporphycenatocobalt(III) with tributyltin hydride generates a cobalt(III)-hydride porphycene detectable by UVvis spectroscopy under diluted conditions, whereas it is impossible to characterize hydride species of cobalt porphyrins. One of the reasons for the stability of the porphycene hydride species is that the porphycene ring has a lower LUMO energy level due to the decrease in the symmetry of the ligand character. However, the hydride species in a highly concentrated solution of the complex is easily converted into the cobalt(II) species via dimerization or reaction of the hydride with excess tributyltin hydride through hemolysis of the Sn-H/Co-H bonds. When the Co(III) porphycene is reacted with LiBHEt 3 , the final product is the cobalt(III)-ethyl complex formed by brearrangement during the reaction of the hydride species and diethylborane in a solvent cage. In the reaction of tetrakistrifluoromethylporphycenatocobalt(III) with tributyltin hydride, the dominant reaction pathway includes oneelectron reduction of the porphycene ring together with radical coupling of the tin reagent rather than the net hydride transfer. This finding suggests that the delicate control of the LUMO energy level influences the stability of the hydride species. The tetrapropyl porphycenatocobalt(III) complex with tributyltin or triphenyltin hydride in the presence of AIBN produces the corresponding Co(III)-trialkyltin complex. This complex was characterized by 1 H NMR spectroscopy. isolable in air in air Co III Bu + Bu 2 Sn=O etc. 1-Co III -SnBu 3 1-Co III -SnPh 3 Scheme 4. Reaction of 1-Co(II) with trialkyltin hydride in the presence of AIBN J. Porphyrins Phthalocyanines 2012.16:616-625. Downloaded from www.worldscientific.com by UNIVERSITY OF SASKATCHEWAN on 02/05/15. For personal use only.

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Co(III)−Alkyl Complex- and Co(III)−Alkylperoxo Complex-Catalyzed Triethylsilylperoxidation of Alkenes with Molecular Oxygen and Triethylsilane

Cited by 121 publications

References 41 publications

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

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

Spiroadamantyl 1,2,4-trioxolane, 1,2,4-trioxane, and 1,2,4-trioxepane pairs: Relationship between peroxide bond iron(II) reactivity, heme alkylation efficiency, and antimalarial activity

Reaction of cobalt porphycene with hydride reagents: spectroscopic detection of Co–H porphycene species and formation of Co–SnR₃ porphycene species

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Co(III)−Alkyl Complex- and Co(III)−Alkylperoxo Complex-Catalyzed Triethylsilylperoxidation of Alkenes with Molecular Oxygen and Triethylsilane

Cited by 121 publications

References 41 publications

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

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

Spiroadamantyl 1,2,4-trioxolane, 1,2,4-trioxane, and 1,2,4-trioxepane pairs: Relationship between peroxide bond iron(II) reactivity, heme alkylation efficiency, and antimalarial activity

Reaction of cobalt porphycene with hydride reagents: spectroscopic detection of Co–H porphycene species and formation of Co–SnR3 porphycene species

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Reaction of cobalt porphycene with hydride reagents: spectroscopic detection of Co–H porphycene species and formation of Co–SnR₃ porphycene species