Catalytic formation of C–O bonds by alkene activation: Lewis acid-cycloisomerisation of olefinic alcohols

Coulombel, Lydie; Favier, Isabelle; Duñach, Élisabet

doi:10.1039/b501601k

Cited by 81 publications

(84 citation statements)

References 12 publications

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“…[205] Kürzlich wurde über die intermolekulare Hydroalkoxylierung nichtaktivierter Olefine in Gegenwart von Alkoholen berichtet, die durch Sn(NTf 2 ) 4 oder Sn(OTf) 4 katalysiert wurde. [206] Eine effiziente intramolekulare Variante dieser Reaktion war zuvor als Katalyse mit Sn(OTf) 4, [207] Al-(OTf) 3, [208] und TfOH [209] beschrieben worden. Für die intermolekulare Addition wurden hauptsächlich natürliche Terpenderivate in Alkoholen als Lösungsmitteln verwendet.…”

Section: Kohlenstoff-sauerstoff-verknüpfungenunclassified

Metalltriflimidate sind bessere Katalysatoren für die organische Synthese als Metalltriflate – der Effekt eines stark delokalisierten Gegenions

2010

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Der steigende Bedarf an neuen selektiven und umweltverträglichen Methoden in der organischen Synthese treibt die Entwicklung effizienterer Reaktionssysteme an. In diesem Zusammenhang hat man sich häufig auf Übergangsmetalle, Liganden und Additive konzentriert; dem Gegenion des Metallkations wurde weniger Aufmerksamkeit geschenkt. Kürzlich wurden Metallsalze mit einem oder mehreren Triflimidat‐Gegenion(en) (Tf2N−) beschrieben. Triflimidate bilden eine einzigartige Katalysatorklasse mit außergewöhnlicher σ‐ und π‐Lewis‐Acidität, die durch die starke Delokalisierung der Ladung im Triflimidation sowie seine sterische Hinderung begründet wird. Daher wird praktisch kein nucleophiles Verhalten und eine hohe positive Ladungsdichte am Metallkation beobachtet, die seine Lewis‐Acidität verstärkt. Folglich sind Metalltriflimidate häufig effizienter als entsprechende ‐halogenide oder ‐triflate. Dieser Aufsatz beschreibt Methoden zur Herstellung von Metalltriflimidaten und deren Einsatz als Katalysatoren.

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Section: Kohlenstoff-sauerstoff-verknüpfungenunclassified

Metalltriflimidate sind bessere Katalysatoren für die organische Synthese als Metalltriflate – der Effekt eines stark delokalisierten Gegenions

2010

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“…The search for a specific metal catalyst for hydroalkoxylation [4a, 5-7] of nonactivated alkenes, using the reaction of Scheme 1 as a model reaction, was initiated by a 1998 report on a ruthenium triflate catalyst. [18][19][20] Since then, numerous similar reports on catalysis with ZrCl 4 , [21] Sn(OTf) 4 , [22] Al(OTf) 3 , [23] Cu(OTf) 2 or AgOTf, [24] Ln(OTf) 3 in ionic liquids, [25,26] or with Au(PPh 3 )OTf [27] have appeared. Related catalysts were also reported for the tandem conversion of allyl aryl ethers, via 2-allylphenols to coumarans.…”

Section: Introductionmentioning

confidence: 99%

Aluminum‐Catalyzed Hydroalkoxylation at Elevated Temperatures: Fast and Simple Access to Coumarans and Other Oxygen Heterocycles

2013

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An aluminum‐catalyzed intramolecular hydroalkoxylation of nonactivated alkenes is presented as a powerful synthetic tool for the preparation of oxygen heterocycles, which are of major interest for the preparation of biological and pharmaceutical active compounds. The aluminum isopropoxide catalyzed (5 mol %) cyclization of 2‐allylphenols at elevated temperatures (250 °C, 20 min) provides 2‐methylcoumarans (2‐methyl‐2,3‐dihydrobenzofuran) in an exceptionally fast, simple, and economic manner. Moreover, heating of allyl aryl ethers with aluminum isopropoxide (5 mol %) gives 2‐methylcoumarans by a tandem Claisen rearrangement–hydroalkoxylation reaction. For either reaction, the catalyst tolerates a broad scope of substrates with various functional groups. By using the weakly electrophilic aluminum alkoxide as the catalyst, occurrence of “hidden Brønsted acid” catalysis can be excluded under the present reaction conditions.

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“…[2] Although this reaction is known to be catalyzed by Brønsted acids in superstoichiometric amounts, we recently reported the use of tin(iv) triflate as catalyst for the hydroalkoxylation of unactivated alkenes. [3] Indeed, the highly Lewis acidic character of this catalyst is due to the strongly electron withdrawing trifluoromethanesulfonate group. [4] The use of transition-metal catalysis for selective hydroalkoxylation of unsaturated hydrocarbons [5] has been reported in the cases of CC [6] and activated C=C bonds such as allenes, [7] 1,3-dienes [8] and Michael acceptors.…”

Section: Introductionmentioning

confidence: 99%

Aluminium(III) Trifluoromethanesulfonate as an Efficient Catalyst for the Intramolecular Hydroalkoxylation of Unactivated Olefins: Experimental and Theoretical Approaches

Coulombel

Rajzmann

Pons

et al. 2006

Chemistry A European J

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114

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The Al(OTf)(3)-catalyzed cycloisomerization of unactivated unsaturated alcohols was studied from experimental and theoretical points of view. A series of cyclic ethers was obtained in excellent yields and regioselectivities. This catalyst system provides one of the most straightforward routes to cyclic ethers with Markovnikov-type regioselectivity under mild conditions. Theoretical and NMR studies were carried out in order to better determine the mechanism of this reaction. The NMR studies were in agreement with preferential complexation of Al(OTf)(3) to the oxygen atom of the unsaturated alcohol, but did not exclude complexation to the double bond of the alcohol. Theoretical calculations indicated strong acidification of the hydroxyl proton when Al(OTf)(3) was complexed to the alcohol oxygen atom. A plausible catalytic cycle for the Al(OTf)(3)-catalyzed intramolecular hydroalkoxylation of unactivated olefins is proposed.

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Catalytic formation of C–O bonds by alkene activation: Lewis acid-cycloisomerisation of olefinic alcohols

Abstract: Tin(IV) trifluoromethanesulfonate has been found to be an excellent catalyst for the cycloisomerisation of non-activated and differently substituted olefinic alcohols to cyclic ethers.

Cited by 81 publications

References 12 publications

Metalltriflimidate sind bessere Katalysatoren für die organische Synthese als Metalltriflate – der Effekt eines stark delokalisierten Gegenions

Metalltriflimidate sind bessere Katalysatoren für die organische Synthese als Metalltriflate – der Effekt eines stark delokalisierten Gegenions

Aluminum‐Catalyzed Hydroalkoxylation at Elevated Temperatures: Fast and Simple Access to Coumarans and Other Oxygen Heterocycles

Aluminium(III) Trifluoromethanesulfonate as an Efficient Catalyst for the Intramolecular Hydroalkoxylation of Unactivated Olefins: Experimental and Theoretical Approaches

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