A Robust and Broadly Applicable Cobalt‐Catalyzed Cross‐Coupling of Functionalized Bench‐Stable Organozinc Pivalates with Unsaturated Halides

Abstract

We report a robust and broadly applicable CoCl -catalyzed cross-coupling between functionalized aryl and heteroaryl zinc pivalates and various electron-poor aryl and heteroaryl halides (X=Cl, Br, I). Couplings with (E)- or (Z)-bromo- or iodo-alkenes proceed with retention of configuration. Also, alkynyl bromides react with arylzinc pivalates providing arylated alkynes.

Cobalt‐Catalyzed Cross‐Couplings between Alkenyl Acetates and Aryl or Alkenyl Zinc Pivalates

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CoBr 2 (5 mol %) in the presence of 2,2'-bipyridyl (5 mol %) enables electrophilic alkenylations between easily accessible alkenyl acetates or tosylates and various functionalized aryl zinc pivalates at ambient temperature.This cobaltcatalyzedp rocess was further applicable to alkenyl zinc pivalates to provide substituted 1,3-dienes.Cobalt-catalyzed cross-couplings [1] are industrially and ecologically friendly carbon-carbon bond-forming reactions because cobalt salts display low toxicity [2] and require only simple ligands. [3,4] Aryl and heteroaryl magnesium [5] or zinc reagents are especially attractive because these organometallic species are compatible with avariety of functional groups. Of special interest are aryl zinc pivalates,w hich show enhanced air and moisture stability and can be stored as solids under argon atmosphere for several months.

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Cobalt‐Catalyzed Electrophilic Amination of Aryl‐ and Heteroarylzinc Pivalates with N‐Hydroxylamine Benzoates

“…Over the past two decades,t he development of palladiumcatalyzed Buchwald-Hartwig nucleophilic aminations [2] allowed the facile synthesis of aryl amines.H owever,t hese reactions usually require expensive catalysts and ligands. [10][11][12] These reagents were used to improve the efficiency of cobalt-catalyzed Negishi crosscoupling reactions [11] and were useful for the synthesis of biologically active molecules [12] as well as high-throughput screenings. [3] This amination [4] has been extended to organometallic compounds derived from Mg, [3d] Zn, [5] Al, [6] B, [7] Si, [8] and Cu [9] by using Cu or Ni as catalysts.Despite the impressive progress made,the use of air-sensitive reagents,ligands,ortoxic Ni catalysts still represent drawbacks.R ecently,w er eported an ew class of highly functionalized organozinc reagents with enhanced airand moisture-stability.…”

“…[3] This amination [4] has been extended to organometallic compounds derived from Mg, [3d] Zn, [5] Al, [6] B, [7] Si, [8] and Cu [9] by using Cu or Ni as catalysts.Despite the impressive progress made,the use of air-sensitive reagents,ligands,ortoxic Ni catalysts still represent drawbacks.R ecently,w er eported an ew class of highly functionalized organozinc reagents with enhanced airand moisture-stability. [10][11][12] These reagents were used to improve the efficiency of cobalt-catalyzed Negishi crosscoupling reactions [11] and were useful for the synthesis of biologically active molecules [12] as well as high-throughput screenings. [13] Herein, we describe the first cobalt-catalyzed electrophilic amination of organozinc pivalates with Obenzoylhydroxylamines.T he reaction scope is especially broad, allowing the preparation of tertiary diarylalkylamines not available by copper-o rn ickel-catalyzed aminations.…”

Cobalt‐katalysierte Kreuzkupplung zwischen Alkenylacetaten und Aryl‐ oder Alkenylzinkpivalaten

“…Zusätzlich wurded ie Cobaltkatalyse auf Alkenylzinkpivalate angewendet, um substituierte 1,3-Diene zu erhalten.Cobalt-katalysierte Kreuzkupplungen [1] sind industrie-und umweltfreundliche Reaktionen, um Kohlenstoff-Kohlenstoff-Bindungen zu knüpfen, da Cobaltsalze eine geringe Toxizität [2] aufweisen und nur einfache Liganden erfordern. [3,4] Aryl-und Heteroarylmagnesium- [5] oder Zinkreagentien sind besonders attraktiv,dadiese organometallischen Reagentien mit verschieden funktionellen Gruppen kompatibel sind. Von besonderem Interesse sind Arylzinkpivalate,die eine erhçhte Luft-und Feuchtigkeitsstabilitätaufweisen und als Feststoffe fürm ehrere Monate unter Argon gelagert werden kçnnen.…”

“…[6] Diese Zinkreagentien [7] gehen Cobalt-katalysierte Kreuzkupplungen mit verschiedenen ungesättigten Halogeniden ein. [3] Ungesättigte Pivalate und Acetate wurden bisher als elektrophile Partner für übergangsmetallkatalysierte Kreuzkupplungen mit B-, Si-, Zn-, Al-und Mg-Reagentien unter Ni-, [8] Rh- [9] oder Fe-Katalyse [10] verwendet. Tr otz dieser großen Fortschritte bleibt die Verwendung von giftigen Rhund Ni-Katalysatoren ein Nachteil.…”