Palladium-Catalyzed Regioselective Arylation of Imidazo[1,2-b][1,2,4]triazine:  Synthesis of an α2/3-Selective GABA Agonist

Gauthier, Donald R.; Limanto, John; Devine, Paul N.; Desmond, Richard; Szumigala, Ronald H.; Foster, Bruce S.; Volante, R. P.

doi:10.1021/jo0507035

Cited by 66 publications

(33 citation statements)

References 35 publications

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“…Synthetic targets included, prodigiosines [198], chartelline alkaloids [199], eupomatilone-3 [200], 9,10-deoxytridachione [201], hamigeran B [202], leprapinic acid and calycin [203], dehydrocoelenterazine analogs [204], gymnocin A (Eq. (11)) [205], murrastifoline A [206], styelsamine C and norsegoline [207], trispheridine [208], dragmacin F [209], ningalin D [210], eupomatilones [211], lucilactaene [47], epoxyquinols A-C and epoxytwinol A [212], mukonine [213], cepharanone [214], ␣ v ␤ 3 antagonist [215], alternariol [216], core of roseophilin [21], (−)-callystatin A [217], dibenzo[c,p]chrysene [218], GABA agonist [219,220], diazonamide A [221], dityrosine, trityrosine, pulcherosine [222], lamellarin D [223], integramycin [224], (+)-discodermolide and analogues [225,226], AB-ring system of hexacyclinic acid [227], ␦-trans-tocotrienoloic acid [135], spirofungins [228], kwakhurin [229], toward (+)-and (−)-deplanchein [230], combretastatin analogs [231], diazonamide A [75], cadiolide B [232], pukeleimide A [233], toward apoptolidin [234], polycitone A and B …”

Section: Carbon-carbon Bond-forming Reactions Via Transmetallationmentioning

confidence: 99%

“…The palladium-catalyzed intramolecular variation ("aromatic-Heck") using aromatic rings in place of alkenes in couplings with organic and halides and triflates [392][393][394] was used to prepare benanomicin B [395], cavicularin and riccardin C [396], 5,6-dihydro-4H,8H-pyrido[3,2,1-de]phenanthridin-8-one [397], GABA agonist [219,220], lamellarin D and lamellarin analogs [223,240], allocolchicinoid [341], rhazinilam [398], givocarcin M [399], isoneocryptolepine [400], graphislactones A-D [401] and fused benzazepinones [402].…”

Section: Carbon-carbon Bond-forming Reactions Using Terminal Alkynes mentioning

confidence: 99%

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Transition metals in organic synthesis: Highlights for the year 2005

Söderberg

2008

Coordination Chemistry Reviews

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Section: Carbon-carbon Bond-forming Reactions Via Transmetallationmentioning

confidence: 99%

Section: Carbon-carbon Bond-forming Reactions Using Terminal Alkynes mentioning

confidence: 99%

Transition metals in organic synthesis: Highlights for the year 2005

Söderberg

2008

Coordination Chemistry Reviews

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“…Eine C-HArylierungsmethode ermçglichte in der Synthese von Piperarborenin B (6) [23] einen fantasievollen strategischen Bindungsbruch, um das unsymmetrisch substituierte Diarylcyclobutangerüsts aufzubauen (diese Strukturelemente wurden allgemein durch [2+2]-Photocycloaddition hergestellt). Die technische Synthese von Verbindungen durch C-H-Funktionalisierung kommt langsam zur Anwendung, wie die industrielle Synthese von Flubendiamid (7) [24] und die Synthese des GABA-Agonisten 8 im Kilogramm-Maßstab [25] beispielhaft zeigen. Demzufolge hat mit der Einführung der C-HFunktionalisierung in Bezug auf die Art und Weise, wie biologisch aktive Verbindungen synthetisiert werden, eine Revolution begonnen.…”

Section: üBerblick üBer C-h-funktionalisierungen Undunclassified

Funktionalisierung von C‐H‐Bindungen: neue Synthesemethoden für Naturstoffe und Pharmazeutika

2012

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Die direkte Funktionalisierung von C‐H‐Bindungen in organischen Molekülen hat sich in jüngster Zeit zu einer wirksamen und idealen Methode entwickelt, mit der Kohlenstoff‐Kohlenstoff‐ und Kohlenstoff‐Heteroatom‐Bindungen geknüpft werden können. Der Aufsatz gibt einen Überblick über die Strategien, die durch Funktionalisierung von C‐H‐Bindungen eine rasche Synthese von biologisch aktiven Verbindungen wie Naturstoffen und pharmazeutischen Zielsubstanzen ermöglichen.

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“…The key to success was the optimum combined choice of the catalyst, solvent, and oxidant. Initial investigations consisted of testing the reaction conditions reported for the oxidative dimerization of an imidazotriazine 16 [Pd(OAc) 2 (10 mol%), KOAc (2 equiv)]. Under these conditions, the coupling between 2-phenylimidazo[1,2-a]pyridine (4) and methyl acrylate (4 equiv) in N,N-dimethylformamide at 120°C for 60 hours using either O 2 or air as oxidant led to the formation of the…”

mentioning

confidence: 99%

“…HRMS: m/z [M + H + ] calcd for C16 H 12 N 3 : 246.1031; found: 246.1033. 61-7.69 (m, 3 H), 7.90 (d, J = 16.5 Hz, 1 H), 8.37 (d, J = 7 Hz, 1 H).…”

mentioning

confidence: 99%

Pd/Cu-Catalyzed Oxidative C-H Alkenylation of Imidazo[1,2-a]pyridines

Koubachi¹,

Berteina‐Raboin²,

Mouaddib³

et al. 2008

Synthesis

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A novel direct and regioselective Pd/Cu-catalyzed intermolecular oxidative coupling of imidazo[1,2-a]pyridines with alkenes was successfully developed. The scope and limitations of the reaction were further studied by using various alkenes. This method provides a 'green' route to 3-alkenylimidazo[1,2-a]pyridine derivatives in high yields.The ability to form C-C bonds is an indispensable tool in synthetic organic chemistry, and the development of powerful catalytic methods has opened new routes to complex molecule synthesis. Usually, heteroaryl-aryl bonds are formed by the coupling of two functionalized heteroaromatic carbons, but that is not always necessary. It is sometimes possible to directly arylate an aromatic ring by replacing a C-H bond with a C-C bond. In the past three decades, the development of transition-metal-catalyzed C-H activation reactions has received considerable attention. 1 A wide range of metal catalysts, including Ru, Rh, Pt, and Pd catalysts, have been exploited with varying levels of success.Considering the remarkable progress made in the development of palladium-catalyzed C-C bond-forming reactions of various heterocycles, 2,3 we turned our attention to intermolecular C-H alkenylation via oxidative Pd/Cu-catalyzed reactions. In the recent years a limited number of methods for regioselective couplings of heteroaromatic systems using oxidative palladium-catalyzed reactions of arenes and olefins have been described; 4 however, in some cases, these procedures have shown moderate regioselectivity. 4Our group has a long-standing interest in imidazo[1,2-a]pyridine derivatives. 5 We have reported a regioselective palladium-catalyzed (hetero)arylation 6 at C-3 of imidazo[1,2-a]pyridines and the first examples of one-pot, twostep Suzuki cross-coupling/direct arylation and one-pot, three-step cyclization/Suzuki cross-coupling/regioselective arylation. 7 Herein, we describe recent advances in the direct and regioselective alkenylation of imidazo[1,2-a]pyridines by oxidative Pd/Cu-catalyzed C-H bond activation (Scheme 1). As far as we know, this is the first example of intermolecular oxidative C-3 alkenylation of bicyclic heterocycles with a bridgehead nitrogen atom.To the best of our knowledge, few approaches, including palladium cross-coupling, are known for preparing 3-alkenylimidazo[1,2-a]pyridines 3 from imidazo[1,2-a]pyridines 1 (Scheme 1): pathway A, involving halogenation of imidazo[1,2-a]pyridines 1 5a,8-10 followed by Heck,5a,8,11 Stille, 12 or Suzuki 13 cross-coupling; pathway B, involving bromination of alkene followed by the 'inverse' Heck reaction. 14 Although these sequences were successful, an additional step for the activation of imidazo[1,2-a]pyridines and alkenes is required and expensive reagents are used (alkenylboronic acids for Suzuki and alkenylstannanes for Stille couplings). Compared to these methods, the oxidative alkenylation reaction is obviously advantageous in terms of starting material price and byproduct (i.e., brominated alkene) formation.

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Palladium-Catalyzed Regioselective Arylation of Imidazo[1,2-b][1,2,4]triazine: Synthesis of an α_2/₃-Selective GABA Agonist

Cited by 66 publications

References 35 publications

Transition metals in organic synthesis: Highlights for the year 2005

Transition metals in organic synthesis: Highlights for the year 2005

Funktionalisierung von C‐H‐Bindungen: neue Synthesemethoden für Naturstoffe und Pharmazeutika

Pd/Cu-Catalyzed Oxidative C-H Alkenylation of Imidazo[1,2-a]pyridines

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