A New One‐Pot Synthetic Approach to the Highly Functionalized (<i>Z</i>)‐2‐(Buta‐1,3‐dienyl)phenols and 2‐Methyl‐2<i>H</i>‐chromenes: Use of Amine, Ruthenium and Base‐Catalysis

Ramachary, Dhevalapally B.; Narayana, Vidadala V.; Ramakumar, Kinthada

doi:10.1002/ejoc.200800472

Cited by 47 publications

(21 citation statements)

References 19 publications

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“…In the next step, allene coordination is followed by migratory insertion to give the pallylic rhodacycle C. This intermediate, instead of undergoing a reductive elimination, evolves through b-hydride elimination [12] to give the conjugated system D, an intermediate poised to undergo a [1,7]-proton transfer to generate the dearomatized enone E, which evolves by means of a 6pelectrocyclic reaction to the observed chromene. [13] The rhodium(I) species generated in the catalytic cycle is reoxidized by Cu(OAc) 2 to the give active rhodium(III) species.…”

Section: Angewandte Zuschriftenmentioning

confidence: 99%

Rhodium‐Catalyzed (5+1) Annulations Between 2‐Alkenylphenols and Allenes: A Practical Entry to 2,2‐Disubstituted 2H‐Chromenes

et al. 2015

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Abstract:Readily available alkenylphenols react with allenes under rhodium catalysis to provide valuable 2,2-disubstituted 2H-chromenes. The whole process, which involves the cleavage of one C-H bond of the alkenyl moiety and the participation of the allene as 1C cycloaddition partner, can be considered as a simple, versatile and atom economical (5+1) hetero-annulation. The reaction tolerates a broad range of substituents both in the alkenylphenol and in the allene, and most probably proceeds through a mechanism involving a Rh-catalyzed C-C coupling followed by two sequential pericyclic processes.In recent years there has been a boost in the development of transition-metal catalyzed reactions involving the cleavage of non-activated C-H bonds. [1] While in most of the cases these reactions entail functionalization processes, over the last years there have been also many reports on the development of annulation reactions. [2] In this context, we recently demonstrated that 2-alkenylphenols can be engaged in interesting annulations with alkynes using Rh(III) oxidative catalysis [Eq. (1); Scheme 1]. [3] These reactions have been proposed to involve the formation of six-membered rhodacycles of type A. The synthetic and mechanistic relevance of the transformation called for exploring the performance of unsaturated partners other than alkynes. In particular, we were interested in checking the reactivity of allenes, very attractive unsaturated systems that have been scarcely studied in reactions involving the cleavage of C-H bonds. [4,5] Scheme 1. Oxidative annulations of 2-alkenylphenols.

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Section: Angewandte Zuschriftenmentioning

confidence: 99%

Rhodium‐Catalyzed (5+1) Annulations Between 2‐Alkenylphenols and Allenes: A Practical Entry to 2,2‐Disubstituted 2H‐Chromenes

et al. 2015

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“…A related approach has been reported with the synthesis of a functionalized benzo[b]oxepine through ene-yne metathesis and its subsequent base-mediated ring opening to form a 1substituted [3]dendralene. [98] Bruneau and co-workers have recently described a different ene-yne metathesis/elimination sequence to substituted [3]dendralenes. [99] This new approach involves metathesis between propargylic carbonates and ethylene.…”

Section: Acyclic Dendralene Derivativesmentioning

confidence: 99%

Dendralenes Branch Out: Cross‐Conjugated Oligoenes Allow the Rapid Generation of Molecular Complexity

2012

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Twenty-seven years ago, H. Hopf published the only previous comprehensive review on branched oligoenes that had the title "Dendralenes: A Neglected Family of Hydrocarbons". The dendralenes are no longer neglected. Research into the synthesis, properties, and applications of dendralenes is rapidly gaining momentum and this Review summarizes important recent findings. From significant fundamental properties (the first demonstration of alternating behavior since the annulenes) through to unparalleled complexity-generating synthetic transformations, this fundamental oligoene family is coming of age. Effective synthetic approaches to cyclic and acyclic dendralene systems are analyzed and classified. The most powerful synthetic transformations of the dendralenes, diene-transmissive Diels-Alder reactions, are surveyed in detail.

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“…Ein ähnlicher Syntheseweg umfasst die Synthese eines funktionalisierten Benzo[b]oxepins durch Eninmetathese und seine anschließende baseninduzierte Ringçffnung zum 1-substituierten [3]Dendralen. [98] Bruneau und Mitarbeiter haben 2009 eine andere Eninmetathese-Eliminierungs-Sequenz zu einem substituierten [3]Dendralen beschrieben. [99] [102] Erneut wurde eine komplette Spaltung der C=C-Bindung in TTF beobachtet, und die ringgeçffneten Produkte 135, hochfunktionalisierte [3]Dendralene, wurden isoliert, vermutlich wieder über ein Cyclobuten-Intermediat 134.…”

Section: Acyclische Dendralenderivateunclassified

Dendralene auf dem Vormarsch: kreuzkonjugierte Oligoene ermöglichen den schnellen Aufbau molekularer Komplexität

Hopf

Sherburn

2012

Angewandte Chemie

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Vor 27 Jahren veröffentlichte H. Hopf den bisher einzigen umfassenden Übersichtsartikel zu verzweigten Oligoenen mit dem Titel “Dendralene – eine vernachlässigte Gruppe hochungesättigter Kohlenwasserstoffe”. Die Dendralene werden heutzutage nicht mehr vernachlässigt. Die Forschung zu Synthese, Eigenschaften und Anwendungen der Dendralene hat in jüngster Zeit viele neue Impulse erhalten, und der vorliegende Aufsatz fasst die bedeutenden Ergebnisse der letzten Jahre zusammen. Von grundlegend wichtigen Eigenschaften (der ersten Demonstration von alternierendem Verhalten seit den Annulenen) bis zu unvergleichbaren, molekulare Komplexität erzeugenden, chemischen Transformationen: Die als Dendralene bekannte Klasse der Oligoene ist erwachsen geworden! Die verschiedenen Synthesewege zu acyclischen und cyclischen Dendralenen werden analysiert und klassifiziert. Die leistungsfähigste Umwandlung der Dendralene – die Dien‐transmissive Diels‐Alder‐Reaktion (DTDA‐Reaktion) – wird in einer detaillierten Übersicht vorgestellt.

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A New One‐Pot Synthetic Approach to the Highly Functionalized (Z)‐2‐(Buta‐1,3‐dienyl)phenols and 2‐Methyl‐2H‐chromenes: Use of Amine, Ruthenium and Base‐Catalysis

Cited by 47 publications

References 19 publications

Rhodium‐Catalyzed (5+1) Annulations Between 2‐Alkenylphenols and Allenes: A Practical Entry to 2,2‐Disubstituted 2H‐Chromenes

Rhodium‐Catalyzed (5+1) Annulations Between 2‐Alkenylphenols and Allenes: A Practical Entry to 2,2‐Disubstituted 2H‐Chromenes

Dendralenes Branch Out: Cross‐Conjugated Oligoenes Allow the Rapid Generation of Molecular Complexity

Dendralene auf dem Vormarsch: kreuzkonjugierte Oligoene ermöglichen den schnellen Aufbau molekularer Komplexität

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