Catalytic Hydroamination of Unactivated Olefins Using a Co Catalyst for Complex Molecule Synthesis

Shigehisa, Hiroki; Koseki, Natsumi; Shimizu, Nao; Fujisawa, Mayu; Niitsu, Makoto; Hiroya, Kou

doi:10.1021/ja507295u

Cited by 158 publications

(86 citation statements)

References 60 publications

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“…Finally, the carbocation 70 would be trapped by the alcoholic solvent to form the hydroalkoxylated product 64 and HBF 4 , which could be then neutralized by the pyridine base. The same authors applied this co‐catalyzed formation of a carbocation to hydroamination, hydroarylation, and hydrooxycarbonylation reactions …”

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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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%

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

Komeyama

2019

Asian J Org Chem

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“…[4e] Aconceptually different radical addition with nitroarenes was very recently added to the manifold of net hydroamination processes. [5] Baran et al reported the sequential combination of an Fe-catalyzed hydrogen atom transfer (HAT) [6] and an Fe-catalyzed reductive deoxygenation in ao ne-pot operation that allows the facile preparation of tert-a nd secalkyl aryl amines.B ased on some literature precedents, [7,8] ah ighly practical procedure was developed, which uses various alkenes,aromatic nitro compounds as Nelectrophiles, phenylsilane as the HATreagent, and iron(III) acetylacetonate as the pre-catalyst under thermal conditions (ethanol, 60 8 8C; Scheme 2). Isolated examples of Fe-catalyzed HATt o alkenes and subsequent reactions of the alkyl radicals with 1-butylnitrite to give nitrosoalkanes under similar conditions were reported by Mukaiyama and Kato in 1992.…”

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confidence: 99%

Hydroaminations of Alkenes: A Radical, Revised, and Expanded Version

Villa

Wangelin

2015

Angew Chem Int Ed

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Radical changes: The applicability of alkene hydroamination has recently been significantly expanded by the development of radical variants that are based on initial hydrogen atom transfer to the alkene. This Highlight assesses the current state of the art, focusing on an iron-catalyzed reaction that utilizes stable nitroarenes as the electrophilic N component and is based on the dual catalytic activation of both starting materials.

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“…Building upon extensive recent reports in the area of metal-catalyzed hydrogen-atom transfer reactions to alkenes (MHAT), [10] we surmised that atertiary radical could be easily generated from the 1,1-disubstituted alkenes of type 3,a nd that under appropriate oxidative conditions,s uch as those from the group of Shigehisa, [11,12] cation generation could result by radical oxidation. Depending upon relative rates of oxidation and cyclization, either radical or cationic C À C bond-forming events would take place.Because we were most interested in developing cyclizations with C20 electron-withdrawing groups,w ei nitiated our studies with the diene 5a (Table 1), which was easily assembled by virtue of the oxygenation at C2.…”

Section: Resultsmentioning

confidence: 96%

Cobalt‐Catalyzed Hydrogen‐Atom Transfer Induces Bicyclizations that Tolerate Electron‐Rich and Electron‐Deficient Intermediate Alkenes

Vrubliauskas

Vanderwal

2020

Angewandte Chemie

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A novel CoII‐catalyzed polyene cyclization was developed that is uniquely effective when performed in hexafluoroisopropanol as the solvent. The process is presumably initiated by metal‐catalyzed hydrogen‐atom transfer (MHAT) to 1,1‐disubstituted or monosubstituted alkenes, and the reaction is remarkable for its tolerance of internal alkenes bearing either electron‐rich methyl or electron‐deficient nitrile substituents. Electron‐rich aromatic terminators are required in both cases. Terpenoid scaffolds with different substitution patterns are obtained with excellent diastereoselectivities, and the bioactive C20‐oxidized abietane diterpenoid carnosaldehyde was made to showcase the utility of the nitrile‐bearing products. Also provided are the results of several mechanistic experiments that suggest the process features an MHAT‐induced radical bicyclization with late‐stage oxidation to regenerate the aromatic terminator.

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Catalytic Hydroamination of Unactivated Olefins Using a Co Catalyst for Complex Molecule Synthesis

Cited by 158 publications

References 60 publications

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

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

Hydroaminations of Alkenes: A Radical, Revised, and Expanded Version

Cobalt‐Catalyzed Hydrogen‐Atom Transfer Induces Bicyclizations that Tolerate Electron‐Rich and Electron‐Deficient Intermediate Alkenes

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