Ruthenium(II)‐Catalyzed CH Activation/Alkyne Annulation by Weak Coordination with O<sub>2</sub> as the Sole Oxidant

Warratz, Svenja; Kornhaaß, Christoph; Cajaraville, Ana; Niepötter, Benedikt; Stalke, Dietmar; Ackermann, Lutz

doi:10.1002/anie.201500600

Cited by 249 publications

(109 citation statements)

References 83 publications

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“…These reactions involve carboxylate-directed CÀHa ctivation to give vinylmetal intermediates,w hich immediately undergo cyclization steps before either reductive elimination or protonolysis can occur (Scheme 1a). [15,18] Moreover,i nt he presence of electron-deficient transition-metal catalysts or ruthenium(II), alkynes preferentially react with the nucleophilic carboxylate, to form enol esters,rather than with the CÀHmoiety. [19] This reactivity points to the challenges associated with developing selective C À Hh ydroarylations in the proximity of ar eactive carboxylate.…”

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confidence: 99%

“…Based on the above findings and mechanistic investigations for related processes, [18] atentative catalytic cycle for the ruthenium-catalyzed C À Hh ydroarylation of alkynes can be outlined (Scheme 3). It starts with formation of the cyclometallated ruthenium complex I,w hich coordinates to the alkyne substrate.M igratory insertion affords the sevenmembered alkenyl-ruthenium species II.I np athway a, which predominates in polar solvents,p rotonolysis occurs (or reductive elimination, if the proton resides at the ruthenium), thus releasing the hydroarylation product 3aa.…”

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confidence: 99%

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Regioselective C−H Hydroarylation of Internal Alkynes with Arenecarboxylates: Carboxylates as Deciduous Directing Groups

et al. 2016

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In the presence of catalytic [Ru(p-cym)I 2 ] 2 and the base guanidine carbonate,b enzoica cids react with internal alkynes to give the corresponding 2-vinylbenzoic acids.T his alkyne hydroarylation is generally applicable to diversely substituted electron-rich and electron-poor benzoic and acrylic acids.A ryl(alkyl)acetylenes react regioselectively with formation of the alkyl-branched hydroarylation products,a nd propargylic alcohols are converted into g-alkylidene-d-lactones.T he hydroarylation can also be conducted decarboxylatively with ad ifferent choice of catalyst and reaction conditions.T his reaction variant, which does not proceed via intermediate formation of 2-vinylbenzoic acids,o pens up ar egioselective,w aste-minimized synthetic entry to vinylarenes.Given the prevalence of vinylarene moieties in functional materials,p harmaceuticals,a nd natural products, [1] efficient methods for the construction of this structural motif are constantly sought. Established synthetic approaches include Mizoroki-Heck [2] and Fujiwara-Moritani reactions, [3] as well as various catalytic cross-couplings of organometallic reagents with alkynes. [4] C À Hh ydroarylations of alkynes are advantageous over these processes,b ecause they require neither prefunctionalized substrates nor oxidants.S ince the pioneering studies by Murai and co-workers, [5] various metals have been found to efficiently catalyze the hydroarylation of alkynes,for example Ru, [6] Rh, [7] Re, [8] Co, [9] and others.[10] However, these CÀH functionalizations are highly regioselective only when directed by ketone,p yridine,a mide,s ulfoxide,o ro ther strong directing groups,groups which need to be synthesized in additional reaction steps and are not easily removed.Arguably,t he most advantageous directing groups in ortho-functionalizations are carboxylates,b ecause benzoic acids are widely available in great structural diversity and at low cost, and can subsequently be derivatized further, utilized as leaving groups in decarboxylative couplings, [11] or removed tracelessly by protodecarboxylation.[12] However,t he weak coordinating ability of this group poses additional challenges in the development of regiospecific CÀH-activating processes. In recent years,s ubstantial advances in carboxylate-directed CÀHa ctivation have been made, [13] for example,b yt he groups of Yu, [14] Miura, [15] Ackermann, [16] and Larrosa, [12b,c] as well as our own group. [12d, 17] In this context, oxidative couplings of benzoic acids with alkynes to form isocoumarins,naphthalenes,and other cyclic structures have intensively been studied. These reactions involve carboxylate-directed CÀHa ctivation to give vinylmetal intermediates,w hich immediately undergo cyclization steps before either reductive elimination or protonolysis can occur (Scheme 1a). [15,18] Moreover,i nt he presence of electron-deficient transition-metal catalysts or ruthenium(II), alkynes preferentially react with the nucleophilic carboxylate, to form enol esters,rather than with the CÀHmoiety...

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Regioselective C−H Hydroarylation of Internal Alkynes with Arenecarboxylates: Carboxylates as Deciduous Directing Groups

et al. 2016

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“…Delightfully, ethyl acrylate was also well‐suited under the catalytic conditions, furnishing 3 s – u in good yields (Scheme ) . The protocol was also competent to perform an oxidative annulation between benzoic acid and alkyne at room temperature to produce isocoumarin 5 in 76 % yield (Scheme ) …”

Section: Methodsmentioning

confidence: 99%

Enhancing Ru(II)‐Catalysis with Visible‐Light‐Mediated Dye‐Sensitized TiO₂ Photocatalysis for Oxidative C−H Olefination of Arene Carboxylic Acids at Room Temperature

Dana

Dey

Patil

et al. 2020

Chemistry An Asian Journal

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Erythrosine B sensitized TiO2 photocatalysis has been combined with Ru(II)‐catalysis to accomplish an oxidative olefination/annulation of benzoic acids with activated olefins under mild conditions that tolerates useful functionalities, such as halides, free hydroxy, acetamido, etc. The morphology of the photocatalyst is unaffected during the reaction and it can be reused. Mechanistic studies favor the involvement of a photo‐induced single electron transfer process.

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“…[8] In contrast, we have very recently identified the beneficial effect of carboxylates [9] for aerobic alkyne annulations. [10] Within our program on sustainable C À Hfunctionalizations, [11] we herein report the first ruthenium(II)-catalyzed positional selective alkenylations with O 2 as the sole oxidant. Notable features of the versatile ruthenium oxidase catalysis by direct dioxygen-coupled turnover include:a )anu nparalleled broad substrate scope in aerobic alkenylations,b )sustainable aerobic C À Ha ctivations that produce H 2 Oasthe only by-product, c) exceedingly mild reaction conditions,a nd d) oxidative olefinations with weakly coordinating [12] or removable [13] directing groups (DG;F igure 1).…”

Section: In Memory Of Jonas Bangmentioning

confidence: 99%

Ruthenium Oxidase Catalysis for Site‐Selective C–H Alkenylations with Ambient O₂ as the Sole Oxidant

et al. 2015

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Ruthenium(II) oxidase catalysis by direct dioxygencoupled turnover enabled step-economical oxidative C À H alkenylation reactions at ambient pressure.V ersatile ruthenium(II) biscarboxylate catalysts displayed ample substrate scope and proved applicable to weakly coordinating and removable directing groups.T he twofold CÀHf unctionalization strategy was characterized by exceedingly mild reaction conditions as well as excellent positional selectivity.

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Ruthenium(II)‐Catalyzed CH Activation/Alkyne Annulation by Weak Coordination with O₂ as the Sole Oxidant

Cited by 249 publications

References 83 publications

Regioselective C−H Hydroarylation of Internal Alkynes with Arenecarboxylates: Carboxylates as Deciduous Directing Groups

Regioselective C−H Hydroarylation of Internal Alkynes with Arenecarboxylates: Carboxylates as Deciduous Directing Groups

Enhancing Ru(II)‐Catalysis with Visible‐Light‐Mediated Dye‐Sensitized TiO₂ Photocatalysis for Oxidative C−H Olefination of Arene Carboxylic Acids at Room Temperature

Ruthenium Oxidase Catalysis for Site‐Selective C–H Alkenylations with Ambient O₂ as the Sole Oxidant

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Ruthenium(II)‐Catalyzed CH Activation/Alkyne Annulation by Weak Coordination with O2 as the Sole Oxidant

Cited by 249 publications

References 83 publications

Regioselective C−H Hydroarylation of Internal Alkynes with Arenecarboxylates: Carboxylates as Deciduous Directing Groups

Regioselective C−H Hydroarylation of Internal Alkynes with Arenecarboxylates: Carboxylates as Deciduous Directing Groups

Enhancing Ru(II)‐Catalysis with Visible‐Light‐Mediated Dye‐Sensitized TiO2 Photocatalysis for Oxidative C−H Olefination of Arene Carboxylic Acids at Room Temperature

Ruthenium Oxidase Catalysis for Site‐Selective C–H Alkenylations with Ambient O2 as the Sole Oxidant

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Ruthenium(II)‐Catalyzed CH Activation/Alkyne Annulation by Weak Coordination with O₂ as the Sole Oxidant

Enhancing Ru(II)‐Catalysis with Visible‐Light‐Mediated Dye‐Sensitized TiO₂ Photocatalysis for Oxidative C−H Olefination of Arene Carboxylic Acids at Room Temperature

Ruthenium Oxidase Catalysis for Site‐Selective C–H Alkenylations with Ambient O₂ as the Sole Oxidant