Potassium Carbonate-Promoted Stereospecific 5-<i>Endo</i>-<i>Trig</i> Cyclization of Unactivated Allenes in the Absence of Any Transition Metals

Ohno, Hiroaki; Kadoh, Yoichi; Fujii, Nobutaka; Tanaka, Tetsuaki

doi:10.1021/ol053094w

Cited by 48 publications

(22 citation statements)

References 62 publications

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“…While the use of free amino groups lead to reaction times of several days, with sulfonamides as well as acetyl or Boc protecting groups result in a fast conversion (but with the latter two the diastereoselectivity was low) 314. Ohno, Tanaka, et al have recently shown that the sulfonamides readily cyclize with potassium carbonate in DMF in the absence of any transition‐metal catalyst 315. Lee et al have applied the gold‐catalyzed methodology to the synthesis of bicyclic β‐lactams 316.…”

Section: Nucleophilic Additions To π Systemsmentioning

confidence: 99%

Gold Catalysis

2006

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Catalysis by gold has rapidly become a hot topic in chemistry, with a new discovery being made almost every week. Gold is equally effective as a heterogeneous or a homogeneous catalyst and in this Review we attempt to marry these two facets to demonstrate this new found and general efficacy of gold. The latest discoveries are placed within a historical context, but the main thrust is to highlight the new catalytic possibilities that gold-catalyzed reactions currently offer the synthetic chemist, in particular in redox reactions and nucleophilic additions to pi systems. Indeed gold has proved to be an effective catalyst for many reactions for which a catalyst had not been previously identified, and many new discoveries are still expected.

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Section: Nucleophilic Additions To π Systemsmentioning

confidence: 99%

Gold Catalysis

2006

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“…Während freie Aminogruppen zu einer Reaktionszeit von einigen Tagen führen, ist mit Sulfonamiden sowie der Acetyl‐ oder tert ‐Butoxycarbonyl(Boc)‐Schutzgruppe eine schnelle Umsetzung möglich (mit den beiden zuletzt genannten ist die Diastereoselektivität jedoch niedrig) 314. Ohno, Tanaka et al haben kürzlich gezeigt, dass Sulfonamide auch in Abwesenheit jeglichen Übergangsmetalls mit Kaliumcarbonat in DMF cyclisieren 315. Lee et al haben diese Gold‐katalysierte Methode zur Synthese bicyclischer β‐Lactame genutzt 316.…”

Section: Nucleophile Additionen An π‐Systemeunclassified

Gold‐Katalyse

Hashmi¹,

Hutchings²

2006

Angewandte Chemie

859

208

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Die Katalyse durch Gold ist schnell ein “heißes Thema” der Chemie geworden – fast wöchentlich werden neue Entdeckungen gemacht. Gold ist gleichermaßen als heterogener wie auch als homogener Katalysator aktiv, und im folgenden Aufsatz wollen wir diese beiden Facetten gemeinsam präsentieren, um so die vielfältigen Möglichkeiten der Gold‐Katalyse darzulegen. Die neuesten Entdeckungen werden im historischen Kontext diskutiert, Hauptziel ist aber, die neuen Optionen aufzuzeigen, die Gold‐Katalysatoren dem Synthesechemiker bieten – besonders auf den Gebieten der Redoxreaktionen und nucleophilen Additionen an π‐Systeme. Oft erweist sich Gold sogar als guter Katalysator für zuvor unbekannte Reaktionen, und in diesem Bereich gibt es mit Sicherheit noch viel zu entdecken.

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“…Malonate‐tethered allenyl substrates 1 , 3 , 5 , 7 , 9 , and 13 were prepared from dimethyl 2‐(buta‐2,3‐dien‐1‐yl)malonate10 and benzyl bromide derivatives according to the general procedure. N ‐Ts‐tethered allenyl substrate 11 was prepared from N ‐(buta‐2,3‐dien‐1‐yl)‐4‐methylbenzenesulfonamide11 and p‐tert ‐butyldimethylsilyloxybenzyl bromide according to the general procedure.…”

Section: Methodsmentioning

confidence: 99%

Mechanical relaxation in supercooled liquids of bulk metallic glasses

Wen

Zhao

Pan

et al. 2010

Physica Status Solidi (a)

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We report the mechanical relaxation behaviors in typical supercooled liquids of bulk metallic glasses (BMGs). The metallic supercooled liquids are ideal systems for studying intrinsic motions of glass‐former supercooled liquids because their structure is close to the simple “dense random packing of spheres” model. We show that the primary relaxation in the frequency domain is dissipative and can be described by the empirical Kohlrausch–Williams–Watts function, and the temperature dependence of the primary relaxation time has the Vogel–Fulcher–Tamman form. Beyond the primary relaxation, an excess wing is found on the high‐frequency tail of the primary relaxation. A corresponding shoulder is exhibited at a given frequency in the temperature region below the glass‐transition temperature. The experimental results confirm that the decoupling between the slow β relaxation and the primary (α) relaxation exists in metallic supercooled liquids. Based on the current models of the glass transition, we demonstrate that the dynamically heterogeneity originates in the heterogeneous microstructure of metallic supercooled liquids, and a picture of the heterogeneous microstructure is provided.

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Potassium Carbonate-Promoted Stereospecific 5-Endo-Trig Cyclization of Unactivated Allenes in the Absence of Any Transition Metals

Cited by 48 publications

References 62 publications

Gold Catalysis

Gold Catalysis

Gold‐Katalyse

Mechanical relaxation in supercooled liquids of bulk metallic glasses

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