Dual cobalt–copper light-driven catalytic reduction of aldehydes and aromatic ketones in aqueous media

Call, Arnau; Casadevall, Carla; Acuña‐Parés, Ferran; Casitas, Alicia; Lloret‐Fillol, Julio

doi:10.1039/c7sc01276d

Cited by 77 publications

(80 citation statements)

References 113 publications

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“…2018, 24,2039 -2058 www.chemeurj.org Review Ad ual cobalt-copper catalysis cycle was recently found to enable the reduction of aldehydes and aromatic ketones in aqueous media using trialkylamines as electron donors (ED) (Scheme 20 a). [45] The commonly expected reactivity of aromatic ketones under sufficiently reducing photochemical conditions is the formation of ketyl radicals by SET,f ollowed by dimerization to pinacols. Experiments with cyclopropaner adical clock molecules suggest that aS ET-HATm echanism( HAT = hydrogen atom transfer) is indeed operative but other evidence points towards the involvement of ah ydride-transfer mechanism.…”

Section: Reviewmentioning

confidence: 99%

Photoredox Catalysis with Metal Complexes Made from Earth‐Abundant Elements

Larsen

Wenger

2017

Chemistry A European J

301

249

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Photoredox chemistry with metal complexes as sensitizers and catalysts frequently relies on precious elements such as ruthenium or iridium. Over the past 5 years, important progress towards the use of complexes made from earth-abundant elements in photoredox catalysis has been made. This review summarizes the advances made with photoactive Cr , Fe , Cu , Zn , Zr , Mo , and U complexes in the context of synthetic organic photoredox chemistry using visible light as an energy input. Mechanistic considerations are combined with discussions of reaction types and scopes. Perspectives for the future of the field are discussed against the background of recent significant developments of new photoactive metal complexes made from earth-abundant elements.

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Section: Reviewmentioning

confidence: 99%

Photoredox Catalysis with Metal Complexes Made from Earth‐Abundant Elements

Larsen

Wenger

2017

Chemistry A European J

301

249

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“…[6c, 13] Inspired by these precedents,w ee nvision the in situ photogeneration of low-valent cobalt and nickel complexes that behave as supernucleophiles,capable of activating strong C(sp 3 ) À Cl bonds under visible-light irradiation ( Figure 1). [14] We chose the hex-5-enyl halide 2a as as uitable model substrate for the desired transformation since the Thorpe-Ingold effect provided by the dimalonate unit facilitates the cyclization step (Table 1). [14] We chose the hex-5-enyl halide 2a as as uitable model substrate for the desired transformation since the Thorpe-Ingold effect provided by the dimalonate unit facilitates the cyclization step (Table 1).…”

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confidence: 99%

Reductive Cyclization of Unactivated Alkyl Chlorides with Tethered Alkenes under Visible‐Light Photoredox Catalysis

et al. 2019

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The chemical inertness of abundant and commercially available alkyl chlorides precludes their widespread use as reactants in chemical transformations. Presented in this work is a metallaphotoredox methodology to achieve the catalytic intramolecular reductive cyclization of unactivated alkyl chlorides with tethered alkenes. The cleavage of strong C(sp 3 )−Cl bonds is mediated by a highly nucleophilic low‐valent cobalt or nickel intermediate generated by visible‐light photoredox reduction employing a copper photosensitizer. The high basicity and multidentate nature of the ligands are key to obtaining efficient metal catalysts for the functionalization of unactivated alkyl chlorides.

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“…[39,40] We have thus probed this approach for [(N4Py)Co II (ClO 3 )](ClO 3 ). [41] Electrospray ionization of an acetonitrile solution of [(N4Py)Co II (ClO 3 )](ClO 3 )a fforded the desired cobalt complexes [(N4Py)Co II (ClO 3 )] + (m/z 509) and [(N4Py)Co III (O)] + (1; m/z 221;F igure S1 ai nt he Supporting Information). Furthermore,w ee lectrochemically oxidized the cobalt-chlorate complex in solution using aflow setup ( Figure S2), which allowed us to prepare [(N4Py)Co III (ClO 3 )] 2+ (m/z 254.5) and [(N4Py)Co IV (O)] 2+ (2; m/z 221;F igure S1 b).…”

Section: Resultsmentioning

confidence: 99%

M−O Bonding Beyond the Oxo Wall: Spectroscopy and Reactivity of Cobalt(III)‐Oxyl and Cobalt(III)‐Oxo Complexes

et al. 2019

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Terminal oxocomplexes of late transition metals are frequently proposed reactive intermediates.H owever,t hey are scarcely knownbeyond Group 8. Using mass spectrometry,we prepared and characterized two such complexes: 2+ (2). Infrared photodissociation spectroscopyr evealed that the Co À Ob ond in 1 is rather strong, in accordance with its lacko fc hemical reactivity.O nt he contrary, 2 has av ery weak CoÀOb ond characterized by as tretching frequency of 659 cm À1 .A ccordingly, 2 can abstract hydrogen atoms from non-activated secondary alkanes.P reviously,t his reactivity has only been observed in the gas phase for small, coordinatively unsaturated metal complexes.M ultireference ab-initio calculations suggest that 2,formally acobalt(IV)-oxo complex, is best described as cobalt(III)-oxyl. Our results provide important data on changes to metal-oxo bonding behind the oxow all and show that cobalt-oxo complexes are promising targets for developing highly active C À Ho xidation catalysts.

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Dual cobalt–copper light-driven catalytic reduction of aldehydes and aromatic ketones in aqueous media

Abstract: A dual catalytic system based on earth-abundant elements reduces aromatic ketones and aldehydes to alcohols in aqueous media under visible light. An unprecedented selectivity for the reduction of aromatic ketones versus aliphatic aldehydes is reported.

Cited by 77 publications

References 113 publications

Photoredox Catalysis with Metal Complexes Made from Earth‐Abundant Elements

Photoredox Catalysis with Metal Complexes Made from Earth‐Abundant Elements

Reductive Cyclization of Unactivated Alkyl Chlorides with Tethered Alkenes under Visible‐Light Photoredox Catalysis

M−O Bonding Beyond the Oxo Wall: Spectroscopy and Reactivity of Cobalt(III)‐Oxyl and Cobalt(III)‐Oxo Complexes

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