Cu-catalyzed deoxygenative gem-hydroborylation of aromatic aldehydes and ketones to access benzylboronic esters

Wang, Lu; Sun, Wei; Liu, Chao

doi:10.1016/s1872-2067(18)63139-0

Cited by 25 publications

(8 citation statements)

References 50 publications

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“…4d and e ). Presumably, gem -diboronates could be involved during the reduction of the above-mentioned species 48 , 57 , which was validated by the selective mono-protodeboronation of α , α -benzyldiboronate 2b’ under our optimal conditions.…”

Section: Resultssupporting

confidence: 59%

Direct deoxygenative borylation of carboxylic acids

Huang

Ataya

et al. 2021

Nat Commun

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Carboxylic acids are readily available, structurally diverse and shelf-stable; therefore, converting them to the isoelectronic boronic acids, which play pivotal roles in different settings, would be highly enabling. In contrast to the well-recognised decarboxylative borylation, the chemical space of carboxylic-to-boronic acid transformation via deoxygenation remains underexplored due to the thermodynamic and kinetic inertness of carboxylic C-O bonds. Herein, we report a deoxygenative borylation reaction of free carboxylic acids or their sodium salts to synthesise alkylboronates under metal-free conditions. Promoted by a uniquely Lewis acidic and strongly reducing diboron reagent, bis(catecholato)diboron (B2cat2), a library of aromatic carboxylic acids are converted to the benzylboronates. By leveraging the same borylative manifold, a facile triboration process with aliphatic carboxylic acids is also realised, diversifying the pool of available 1,1,2-alkyl(trisboronates) that were otherwise difficult to access. Detailed mechanistic studies reveal a stepwise C-O cleavage profile, which could inspire and encourage future endeavours on more appealing reductive functionalisation of oxygenated feedstocks.

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Section: Resultssupporting

confidence: 59%

Direct deoxygenative borylation of carboxylic acids

Huang

Ataya

et al. 2021

Nat Commun

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“…Recently, we have demonstrated a rhodium-catalyzed deoxygenation and borylation of ketones for the selective synthesis of alkenes, vinylboronates, and vinyldiboronates (Figure B) . Mechanistically, the ketones undergo a Rh-catalyzed deoxygenation using B 2 pin 2 as a deoxygenative reagent − to deliver the alkenes, followed by a Rh-catalyzed dehydrogenative borylation to give vinylboronate products. − We surmise that if the intermediate A in deoxygenative borylation of ketones − underwent protodemetalation (Figure B) instead of β-hydride elimination, the hydroboration product would be obtained, leading to a practical approach for the preparation of alkylboronates from ketones. Moreover, it would be an important complement and extension to the existing protocols for the synthesis of linear or branched alkylboronates if the regioselectivity of hydroboration could be controlled by ligands.…”

Section: Introductionmentioning

confidence: 99%

Rhodium-Catalyzed Regiodivergent Synthesis of Alkylboronates via Deoxygenative Hydroboration of Aryl Ketones: Mechanism and Origin of Selectivities

Zhang

Tao

et al. 2021

ACS Catal.

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Here, we report an efficient rhodium-catalyzed deoxygenative borylation of ketones to synthesize alkylboronates, in which the regioselectivity can be switched by the choice of the ligand. The linear alkylboronates were obtained exclusively in the presence of P( n Bu)3, and PPh2Me favored the formation of branched alkylboronates. The protocol also allows access to 1,1,2-triboronates from the readily available ketones. Mechanistic studies suggest that this Rh-catalyzed deoxygenative borylation of ketones goes through an alkene intermediate, which undergoes regiodivergent hydroboration to afford linear and branched alkylboronates. The different steric effects of PPh2Me and P( n Bu)3 were found to be responsible for product selectivity by density functional theory calculations. The alkene intermediate can alternatively undergo sequential dehydrogenative borylation and hydroboration to deliver the triboronates.

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“…Our group has been focusing on the development of new methods for the synthesis and application of alkyl-Bpin. [45][46][47][48][49][50][51][52] Considering the challenge of the less reactive Aggarwal group 41,42 Ley and co-workers [38][39][40] Studer group 43 Scheme 1 | (a and b) Photoinduced generation of alkyl radicals from alkyl-Bpin and its application in a transitionmetal-free alkynylation. LG = -SO 2 Ph.…”

Section: Resultsmentioning

confidence: 99%

Photoinduced Transition-Metal-Free Alkynylation of Alkyl Pinacol Boronates

2021

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An unprecedented visible-light-induced transitionmetal-free alkynylation of alkyl pinacol boronates has been demonstrated with alkynyl phenylsulfones as the alkynylation reagents and 4CzIPN as the organic photocatalyst. Common sodium methoxide (NaOMe) or sodium hydroxide (NaOH) was used as the Lewis base to generate photoactive tetra-coordinated boron species. Various functional groups were well tolerated. The selective monoalkynylation of diboronates was achieved to keep one boryl group in the product for potential further transformations. Radical trapping experiments and electron paramagnetic resonance (EPR) analysis confirmed the generation of alkyl radical intermediate.

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Cu-catalyzed deoxygenative gem-hydroborylation of aromatic aldehydes and ketones to access benzylboronic esters

Cited by 25 publications

References 50 publications

Direct deoxygenative borylation of carboxylic acids

Direct deoxygenative borylation of carboxylic acids

Rhodium-Catalyzed Regiodivergent Synthesis of Alkylboronates via Deoxygenative Hydroboration of Aryl Ketones: Mechanism and Origin of Selectivities

Photoinduced Transition-Metal-Free Alkynylation of Alkyl Pinacol Boronates

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