Transition Metal‐Catalyzed Carbon−Carbon Bond Formation with Grignard Reagents − Novel Reactions with a Classic Reagent

Shinokubo, Hiroshi; Oshima, Koichiro

doi:10.1002/ejoc.200300757

Cited by 207 publications

(38 citation statements)

References 102 publications

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“…During the course of our study on transition-metal-catalyzed reaction, 68 readily available cobalt complexes were found to act as catalysts complementary to palladium and nickel in cross-coupling and Mizoroki-Heck reactions. The cobalt-catalyzed reactions probably proceed via carbon-centered radicals as key intermediates that are generated by single electron transfer from electron-rich cobalt complexes to alkyl halides.…”

Section: Halogen-magnesium Exchange Of Alkenyl Halidesmentioning

confidence: 99%

Highly Selective Synthetic Reactions by the Combined Use of Organometallic Reagents and Radical Species

Oshima¹

2008

Bulletin of the Chemical Society of Japan

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During these thirty years, we have pursued new methodologies in organic synthesis and developed many synthetically useful reactions. Among them, four topics are described in this article. (1) Regio-and stereoselective silylmetalation of acetylenes has been examined. Whereas platinum-or copper-catalyzed silylmagnesation of terminal acetylenes afforded (E)-1-silyl-1-alkene exclusively, palladium-catalyzed silylalumination with PhMe 2 Si-AlEt 2 provided 2-silyl-1-alkenes with high regioselectivity. (2) Triethylborane induced radical addition of Ph 3 SnH to acetylenes gave 1-triphenylstannyl-1-alkenes in the presence of small amount of oxygen. The reaction has two distinguishing characteristics. One feature is that Et 3 B can initiate the radical reaction at low temperature, such as À78 C. (3) The other distinctive feature of Et 3 B-induced radical reaction is that many solvents could be used for the reaction. Thus, water was chosen as a solvent, and Et 3 B-induced atom-transfer radical cyclization of iodo acetals and iodoacetates in water was examined. (4) Three types of organometallic ate complexes, R 3 MnMgBr, R 3 MgLi, and R 3 Co(L 2 )MgBr, were prepared and used for organic synthesis. Treatment of gem-dibromocyclopropane with trialkylmanganate provided alkylated cyclopropane after aqueous workup. Aryl and alkenyl halides could be converted into the corresponding magnesium reagents by the action of trialkylmagnesate via halogen-magnesium exchange. Finally, synthetic reactions catalyzed by cobalt complexes are described. Without suffering from -elimination, cobalt complexes allow cross-coupling reactions of alkyl halides with Grignard reagents. Silylmetalation of Acetylenes and Its Application to the Stereoselective Synthesis of Steroidal Side ChainsIn 1982, we started an investigation on the stereoselective synthesis of the side chain of a plant growth steroidal hormone, brassinolide. Our synthesis route, which consists of three key reactions, is shown in Scheme 1.We began by studying the last step (c), selective ring opening of ,-epoxy alcohol. Among many organometallic compounds examined, organoaluminum reagents were found to be effective for the regio-and stereoselective ring opening of epoxy alcohol to give 1,2-diols. 1 The reaction proceeds with inversion at the reacting center. In the next step (b), we had to develop a new method of preparing threo epoxy alcohol 3 form (E)-allylic alcohol 2a. The vanadium-catalyzed epoxidation of (E)-allylic alcohol gave the erythro isomer as a main product. On the other hand, m-CPBA epoxidation gave the threo isomer as a major product, but the selectivities of these reactions were rather low and not enough for our purpose. This problem was solved by substitution of an appropriate hydrogen on the double bond by a bulky Me 3 Si group.2 Treatment of 2b with VO(acac) 2 -t-BuOOH or m-CPBA gave threo epoxy alcohol 3 with high stereoselectivity (99%). The Me 3 Si group was easily removed by treatment with n-Bu 4 NF or CsF in DMSO, and the desilylation of epoxysilane proceeded wi...

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Section: Halogen-magnesium Exchange Of Alkenyl Halidesmentioning

confidence: 99%

Highly Selective Synthetic Reactions by the Combined Use of Organometallic Reagents and Radical Species

Oshima¹

2008

Bulletin of the Chemical Society of Japan

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“…[7,8] Zur Lösung dieses Problems wurde die übergangsmetallkatalysierte Aktivierung dieser Bindung vorgeschlagen, wobei die Wahl des Metalls auf Cobalt fiel, das sich durch eine hohe Reaktivität und niedrige Kosten auszeichnet. [9,10] Hier berichten wir nun über die neuartige Synthese von vielfältig funktionalisierten aromatischen Kupferverbindungen 1 aus Arylsulfonaten 2 durch Cobalt-katalysierten Sulfonat/Kupfer-Austausch mit Phenylkupfer (Schema 1). [11] In unseren Studien zur Cobalt-katalysierten Kreuzkupplung [12] hatten wir beobachtet, dass bei der Reaktion von elektronenarmen p-Tolylsulfonaten (ArOTs) mit PhCu neben dem Kreuzkupplungsprodukt 3 auch eine Arylkupferverbindung 1 entsteht, die aus einem OTs/Cu-Austausch resultiert.…”

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Eine Cobalt‐katalysierte Sulfonat/Kupfer‐Austauschreaktion zur Synthese von elektronenarmen, hoch funktionalisierten Arylkupferreagentien

et al. 2010

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“…[7][8][9][10][11][12][13][14] Eine Lösung dieses Problems ist die Verwendung von racemischen Substraten in Verbindung mit einem chiralen Nickel-Katalysator, der hohe Enantioselektivitäten ergibt. [15,16] Nach unserer Kenntnis gelang die stereoselektive sp 3 -sp 3 -Kreuzkupplung von a-Hydroxyestern bisher nur mit stöchiometrischen Mengen an Übergangsme-tallsalzen, z.…”

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Zink‐katalysierte enantiospezifische sp³‐sp³‐Kreuzkupplung von α‐Hydroxyestertriflaten mit Grignard‐Reagentien

Studte

Breit

2008

Angewandte Chemie

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Zinkchlorid machts möglich und katalysiert die enantiospezifische Kreuzkupplung von α‐Hydroxyestertriflaten mit Grignard‐Reagentien unter milden Bedingungen (siehe Schema). Enantiomerenreine α‐Hydroxyester sind direkt aus dem chiralen Pool oder durch die Diazotierung von α‐Aminosäuren zugänglich. Beide Reaktionspartner können breit variiert werden, und die Umsetzung verläuft mit umgekehrter Polarität wie die klassische Enolatalkylierung.

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Transition Metal‐Catalyzed Carbon−Carbon Bond Formation with Grignard Reagents − Novel Reactions with a Classic Reagent

Cited by 207 publications

References 102 publications

Highly Selective Synthetic Reactions by the Combined Use of Organometallic Reagents and Radical Species

Highly Selective Synthetic Reactions by the Combined Use of Organometallic Reagents and Radical Species

Eine Cobalt‐katalysierte Sulfonat/Kupfer‐Austauschreaktion zur Synthese von elektronenarmen, hoch funktionalisierten Arylkupferreagentien

Zink‐katalysierte enantiospezifische sp³‐sp³‐Kreuzkupplung von α‐Hydroxyestertriflaten mit Grignard‐Reagentien

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Transition Metal‐Catalyzed Carbon−Carbon Bond Formation with Grignard Reagents − Novel Reactions with a Classic Reagent

Cited by 207 publications

References 102 publications

Highly Selective Synthetic Reactions by the Combined Use of Organometallic Reagents and Radical Species

Highly Selective Synthetic Reactions by the Combined Use of Organometallic Reagents and Radical Species

Eine Cobalt‐katalysierte Sulfonat/Kupfer‐Austauschreaktion zur Synthese von elektronenarmen, hoch funktionalisierten Arylkupferreagentien

Zink‐katalysierte enantiospezifische sp3‐sp3‐Kreuzkupplung von α‐Hydroxyestertriflaten mit Grignard‐Reagentien

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Zink‐katalysierte enantiospezifische sp³‐sp³‐Kreuzkupplung von α‐Hydroxyestertriflaten mit Grignard‐Reagentien