Atom‐Economical Synthesis of Unsymmetrical Ketones through Photocatalyzed CH Activation of Alkanes and Coupling with CO and Electrophilic Alkenes

Ryu, Ilhyong; Tani, Akihiro; Fukuyama, Takahide; Ravelli, Davide; Fagnoni, Maurizio; Albini, Angelo

doi:10.1002/ange.201004854

Cited by 59 publications

(16 citation statements)

References 43 publications

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“…Their chemical and physical properties, such as redox potentials, charge‐transfer properties, and acidities, can be accurately controlled by their constituent elements, structures, and charges. By utilizing the intramolecular oxygen‐to‐metal charge transfer of POMs (LMCT) in response to ultraviolet light, they are suitable photocatalysts for various transformations, including functionalization reactions of CH bonds,3a,b H 2 evolution,3c and CO 2 reduction 3d. However, it is difficult to utilize the LMCT by irradiation with visible light ( λ >400 nm) because of the large energy gaps, and therefore, the design of visible‐light‐responsive POM‐based catalysts is required.…”

Section: Methodsmentioning

confidence: 99%

Visible‐Light‐Induced Photoredox Catalysis with a Tetracerium‐Containing Silicotungstate

et al. 2014

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The development of visible-light-induced photocatalysts for chemoselective functional group transformations has received considerable attention. Polyoxometalates (POMs) are potential materials for efficient photocatalysts because their properties can be precisely tuned by changing their constituent elements and structures and by the introduction of additional metal cations. Furthermore, they are thermally and oxidatively more stable than the frequently utilized organometallic complexes. The visible-light-responsive tetranuclear cerium(III)-containing silicotungstate TBA 6 [{Ce(H 2 O)} 2 {Ce(CH 3 CN)} 2 -(m 4 -O)(g-SiW 10 O 36 ) 2 ] (CePOM; TBA = tetra-n-butylammonium) has now been synthesized; when CePOM was irradiated with visible light (l > 400 nm), a unique intramolecular Ce III -to-POM(W VI ) charge transfer was observed. With CePOM, the photocatalytic oxidative dehydrogenation of primary and secondary amines as well as the a-cyanation of tertiary amines smoothly proceeded in the presence of O 2 (1 atm) as the sole oxidant.

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Section: Methodsmentioning

confidence: 99%

Visible‐Light‐Induced Photoredox Catalysis with a Tetracerium‐Containing Silicotungstate

et al. 2014

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“…[13] Organic dyes, for example, the cheap fluoresceins, display similar photocatalytic activity in some reactions [14] and seemed more appropriate as no interference by the presence of carbon monoxide is known. [15] Furthermore, CO only exhibits absorptions in the vacuum-UV range below 180 nm. [16] Our initial studies on the proposed photocatalytic carbonylation with 4-methoxybenzenediazonium tetrafluoroborate (1 a) in methanol were carried out under reaction conditions Scheme 1.…”

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confidence: 99%

Metal‐Free Carbonylations by Photoredox Catalysis

2014

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The synthesis of benzoates from aryl electrophiles and carbon monoxide is a prime example of a transition-metal-catalyzed carbonylation reaction which is widely applied in research and industrial processes. Such reactions proceed in the presence of Pd or Ni catalysts, suitable ligands, and stoichiometric bases. We have developed an alternative procedure that is free of any metal, ligand, and base. The method involves a redox reaction driven by visible light and catalyzed by eosin Y which affords alkyl benzoates from arene diazonium salts, carbon monoxide, and alcohols under mild conditions. Tertiary esters can also be prepared in high yields. DFT calculations and radical trapping experiments support a catalytic photoredox pathway without the requirement for sacrificial redox partners.

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“…Decarbonylation of acyl radicals can be minimized by lowering the reaction temperature (−20–−50 °C), and hydroacylation products were obtained in up to approximately 45 % yield after 24 hours. To overcome this drawback, Ryu, Fagnoni, and co‐workers efficiently generated acyl radicals through carbonylation of alkyl radicals with CO under high pressure (up to 80 atm) 5e. Although this approach is effective toward generation of branched acyl radicals, the applicability is limited to unsubstituted cyclic alkanes because of an issue with site specificity in generating carbon radicals from substituted cyclic or acyclic alkanes.…”

Section: Methodsmentioning

confidence: 99%

Metal‐Free CH Bond Activation of Branched Aldehydes with a Hypervalent Iodine(III) Catalyst under Visible‐Light Photolysis: Successful Trapping with Electron‐Deficient Olefins

et al. 2014

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Direct acyl radical formation of linear aldehydes (RCH 2 -CHO) and subsequent hydroacylation with electrondeficient olefins can be effected with various types of metal and nonmetal catalysts/reagents. In marked contrast, however, no successful reports on the use of branched aldehydes have been made thus far because of their strong tendency of generating alkyl radicals through the facile decarbonylation of acyl radicals. Here, use of a hypervalent iodine(III) catalyst under visible light photolysis allows a mild way of generating acyl radicals from various branched aldehydes, thereby giving the corresponding hydroacylated products almost exclusively. Another characteristic feature of this approach is the catalytic use of hypervalent iodine(III) reagent, which is a rare example on the generation of radicals in hypervalent iodine chemistry.

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Atom‐Economical Synthesis of Unsymmetrical Ketones through Photocatalyzed CH Activation of Alkanes and Coupling with CO and Electrophilic Alkenes

Cited by 59 publications

References 43 publications

Visible‐Light‐Induced Photoredox Catalysis with a Tetracerium‐Containing Silicotungstate

Visible‐Light‐Induced Photoredox Catalysis with a Tetracerium‐Containing Silicotungstate

Metal‐Free Carbonylations by Photoredox Catalysis

Metal‐Free CH Bond Activation of Branched Aldehydes with a Hypervalent Iodine(III) Catalyst under Visible‐Light Photolysis: Successful Trapping with Electron‐Deficient Olefins

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