Transition-metal-promoted 6-endo-dig cyclization of aromatic enynes: rapid synthesis of functionalized naphthalenes

Dankwardt, John W.

doi:10.1016/s0040-4039(01)01146-7

Cited by 173 publications

(81 citation statements)

References 15 publications

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“…[265] In Gegenwart von Wasser reagiert das (2)]. [266][267][268][269] Auch hier ist ein großes Anwendungspotenzial erkennbar, das sich in einem Beispiel im Bereich der Naturstoffchemie bereits materialisiert hat (Abschnitt 5.4). Auf analoge Weise führen Reaktionen mit Enaminen zu Stickstoffheterocyclen [270] oder 1-Aminoacridin-Derivaten [271,272] [Schema 54, Gl.…”

Section: A Fürstner Und P W Daviesunclassified

Katalytische carbophile Aktivierung: Platin‐ und Gold‐π‐Säuren als Katalysatoren

2007

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Platin‐ und Goldkatalysatoren gewinnen aufgrund ihrer hohen Effizienz und erstaunlichen Vielfalt für atomökonomische Umsetzungen rasch an Bedeutung. Dabei erlaubt es die Korrelation zwischen ihrem chemischen Verhalten und den vorhandenen Strukturdaten, der bekannten Koordinationschemie und den auf relativistischen Effekten beruhenden Besonderheiten ihrer metallorganischen Derivate, grundlegende Prinzipien der katalytischen carbophilen Aktivierung durch π‐Säuren zu formulieren. Platin‐ und Goldkomplexe sind keinesfalls nur ein umweltfreundlicher Ersatz für stöchiometrische π‐Säuren, sondern sie erweitern das klassische Reaktivitätsspektrum signifikant. Die in der Literatur geläufigen, aber scheinbar widersprüchlichen Erklärungen ihres Verhaltens auf Basis von Metallcarbenen oder metallstabilisierten, “nichtklassischen” Carbokationen als reaktiven Zwischenstufen liefern bei genauer Betrachtung eine vereinheitlichte Grundlage für das Verständnis dieses faszinierenden Gebiets. Hier gilt das Hauptaugenmerk der Verbesserung bekannter sowie der Entwicklung neuer Kupplungs‐, Cycloisomerisierungs‐ und Gerüstumlagerungsreaktionen. Auch der Einsatz Platin‐ und goldkatalysierter Transformationen in Naturstoffsynthesen wird diskutiert.

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Section: A Fürstner Und P W Daviesunclassified

Katalytische carbophile Aktivierung: Platin‐ und Gold‐π‐Säuren als Katalysatoren

2007

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“…Subsequently Dankwardt demonstrated that apart from the electron rich furan as a nucleophilic reaction partner, also silyl enol ethers like in 40 can be offered intramolecularly (44). In this case the products are functionalized naphthalenes 41.…”

Section: C-c-bond Formationmentioning

confidence: 99%

Homogeneous gold catalysts and alkynes: A successful liaison

2003

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The use of the combination of homogeneous gold-catalysts and alkynes in organic synthesis is reviewed from its beginnings in C-N-bond formation to the newest developments in C-C-bond formation. The common basic principle of these reactions is discussed. Special attention is devoted to the question where the gold catalysts are superior to either other catalysts or more traditional synthetic approaches to the product molecules.Transition metal catalysis has become one of the most important tools in organic synthesis. It allowed entirely new transformations which were not possible previously by "traditional" organic reactions and thus significantly increased the efficiency of synthesis. It also made retrosynthetic analysis more demanding as many of the transformations go along with a remarkable increase in molecular complexity (1) which makes the relationship between the product and the starting material more difficult to recognize. In many of these reactions, especially in the case of late transition metals, C-C multiple bonds in either alkenes or alkynes, are the site of reaction. Theoretical backgroundIn the field of homogeneous gold catalysis the alkynes 1, which have the structural motive of a C-C-triple bond, belong to the most popular substrates. The reason for that popularity is the high reactivity of the alkynes which originates from their electronic structure (2). Often the corresponding alkenes with their C-C-double bond are less reactive.On one hand, the alkynes possess two orthogonal -orbitals high in energy occupied by two electrons each. These react with electrophilic reagents (E) like halogens in organic synthesis or electrophilic metal centers like gold (in the oxidation states I or III) in the field of transition metal catalysis (3,4). In the interaction with a metal center both the -orbital in the plane of metal co-ordination and theorbital perpendicular to it are able to interact with the dorbitals of the metal.On the other hand, the lowest unoccupied orbital of the alkynes is low in energy and thus eagerly react with strong nucleophiles like for example ethyne 2 with catalytical amounts of alkoholates in the Reppe synthesis of vinyl ethers 3 (5).Most unfortunately, weak nucleophiles (Nu) do not react directly with the alkynes, although this is often desired in organic synthesis. But the alkyne can be activated by co-ordination to the electrophilic gold complexes as mentioned above. This co-ordination withdraws electron

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“…[7] In contrast, the substitution pattern of the olefin plays a critical role in the cycloisomerization of ortho-(alkynyl)styrenes (Scheme 1). Thus, the skeletal rearrangement of o-(alkynyl)styrenes -substituted and mono-or non--substituted to produce naphthalenes through a 6-endo cyclization process has been described using complexes derived from several metals such as W, 2 Rh, [9] Ru, [9] Pd, [9][10][11] Pt, [9,11] Ag [12] or Au [9,13] as catalysts (Scheme 1a). Related cycloaromatizations of o-(alkynyl)biaryls also occurred allowing the efficient preparation of substituted phenanthrenes and other polycyclic heteroarenes.…”

Section: Introductionmentioning

confidence: 99%

Gold(I)‐Catalyzed Cycloisomerizations and Alkoxycyclizations of ortho‐(Alkynyl)styrenes

Sanjuán

Rashid

García‐García

et al. 2014

Chemistry A European J

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Abstract:Indenes and related polycyclic structures have been efficiently synthesized by gold(I)-catalyzed cycloisomerizations of appropriate ortho-(alkynyl)styrenes. Disubstitution at the terminal position of the olefin was demonstrated to be essential to obtain products originating from a formal 5-endo-dig cyclization. Interestingly, a complete switch in the selectivity of the cyclization of o-(alkynyl)--methylstyrenes from 6-endo to 5-endo was observed by adding an alcohol to the reaction media. This allowed the synthesis of interesting indenes bearing an all-carbon quaternary center at C-1. Moreover, dihydrobenzo[a]fluorenes can be obtained from substrates bearing a secondary alkyl group at the -position of the styrene moiety by a tandem cycloisomerization/1,2-hydride migration process.In addition, diverse polycyclic compounds were obtained by an intramolecular gold-catalyzed alkoxycyclization of o-(alkynyl)styrenes bearing a nucleophile in their structure. Finally, the use of a chiral gold complex allowed access to elusive chiral 1H-indenes in good enantioselectivities.

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Transition-metal-promoted 6-endo-dig cyclization of aromatic enynes: rapid synthesis of functionalized naphthalenes

Cited by 173 publications

References 15 publications

Katalytische carbophile Aktivierung: Platin‐ und Gold‐π‐Säuren als Katalysatoren

Katalytische carbophile Aktivierung: Platin‐ und Gold‐π‐Säuren als Katalysatoren

Homogeneous gold catalysts and alkynes: A successful liaison

Gold(I)‐Catalyzed Cycloisomerizations and Alkoxycyclizations of ortho‐(Alkynyl)styrenes

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