Isomerization of Allylbenzenes

Hassam, Mohammad; Taher, Abu; Arnott, Gareth E.; Green, Ivan R.; Otterlo, Willem A. L. van

doi:10.1021/acs.chemrev.5b00052

Cited by 256 publications

(200 citation statements)

References 978 publications

(1,312 reference statements)

Supporting

Mentioning

184

Contrasting

Unclassified

Order By: Relevance

“…2!3). [27] Interne Alkene kçnnen somit durch einfache Isomerisierung von terminalen Alkenen unter milden Bedingungen generiert werden, die auch mit komplexeren Substraten kompatibel sind (Schema 4). [23] Die initiale Anregung gewährleistet, dass alle nachgelagerten Reaktionen energetisch abwärts verlaufen und somit die Bildung von thermodynamischen Mischungen, die häufig thermische Reaktionen erschwert (mikroskopische Reversibilität), [24] vermieden wird.…”

Section: Introductionunclassified

Positionelle und geometrische Isomerisierung von Alkenen: der Gipfel der Atomökonomie

2019

View full text Add to dashboard Cite

Strategien zur raumzeitlichen Steuerung von Alkenen durch einen äußeren Reiz sind angesichts der Allgegenwart von Rohstoff‐Olefinen in der Chemie und ihren Folgeanwendungen notwendig. Angelehnt an den 1‐0‐Schalter, der den Sehzyklus von Säugetieren durch eine selektive geometrische Isomerisierung von Retinal ermöglicht, werden Strategien zur geometrischen und positionellen Manipulation des zweidimensionalen Raums von Alkenen mittels chemischer, thermischer und lichtinduzierter Prozesse intensiv untersucht. Dieser Kurzaufsatz beleuchtet den aktuellen Stand der Forschung zur Aktivierung und dem Ermöglichen von Direktionalität in diesen fundamentalen chemischen Transformationen.

show abstract

Section: Introductionunclassified

Positionelle und geometrische Isomerisierung von Alkenen: der Gipfel der Atomökonomie

2019

View full text Add to dashboard Cite

show abstract

“…1 The best results were obtained using Ru(IV) catalysts in homogeneous systems (conversions and trans -anethole selectivities of up to 99%). 16 Alternatively, heterogeneous systems show only moderate selectivities for the trans isomer (85–88%) with conversion of around 86–98%.…”

Section: Introductionmentioning

confidence: 99%

Ru-Catalyzed Estragole Isomerization under Homogeneous and Ionic Liquid Biphasic Conditions

et al. 2017

View full text Add to dashboard Cite

The isomerization of estragole to trans-anethole is an important reaction and is industrially performed using an excess of NaOH or KOH in ethanol at high temperatures with very low selectivity. Simple Ru-based transition-metal complexes, under homogeneous, ionic liquid (IL)-supported (biphasic) and “solventless” conditions, can be used for this reaction. The selectivity of this reaction is more sensitive to the solvent/support used than the ligands associated with the metal catalyst. Thus, under the optimized reaction conditions, 100% conversion can be achieved in the estragole isomerization, using as little as 4 × 10–3 mol % (40 ppm) of [RuHCl(CO)(PPh3)3] in toluene, reflecting a total turnover number (TON) of 25 000 and turnover frequencies (TOFs) of up to 500 min–1 at 80 °C. Using a dimeric Ru precursor, [RuCl(μ-Cl)(η3:η3-C10H16)]2, in ethanol associated with P(OEt)3, a TON of 10 000 and a TOF of 125 min–1 are obtained with 100% conversion and 99% selectivity. These two Ru catalytic systems can be transposed to biphasic IL systems by using ionic-tagged P-ligands such as 1-(3-(diphenylphosphanyl)propyl)-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide immobilized in 1-(3-hydroxypropyl)-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl) imide with up to 99% selectivity and almost complete estragole conversion. However, the reaction is much slower than that performed under solventless or homogeneous conditions. The use of ionic-tagged ligands significantly reduces the Ru leaching to the organic phase, compared to that in reactions performed under homogeneous conditions, where the catalytic system loses catalytic performance after the second recycling. Detailed kinetic investigations of the reaction catalyzed by [RuHCl(CO)(PPh3)3] indicate that a simplified kinetic model (a monomolecular reversible first-order reaction) is adequate for fitting the homogeneous reaction at 80 °C and under biphasic conditions. However, the kinetics of the reaction are better described if all of the elementary steps are taken into consideration, especially at 40 °C.

show abstract

“…[19] Thet etradentate hydrido chloride complex [k 4 -( 15c5 NCOP iPr )Ir(H)(Cl)] (1;t he structure of 15c5 NCOP iPr is shown in Scheme 1) [15] was tested for isomerization activity under standard conditions (5 mm 1 (1 mol %) and 0.5 m allylbenzene in CD 2 Cl 2 ;S cheme 1). [19] Thet etradentate hydrido chloride complex [k 4 -( 15c5 NCOP iPr )Ir(H)(Cl)] (1;t he structure of 15c5 NCOP iPr is shown in Scheme 1) [15] was tested for isomerization activity under standard conditions (5 mm 1 (1 mol %) and 0.5 m allylbenzene in CD 2 Cl 2 ;S cheme 1).…”

mentioning

confidence: 99%

“…[19] Thet etradentate hydrido chloride complex [k 4 -( 15c5 NCOP iPr )Ir(H)(Cl)] (1;t he structure of 15c5 NCOP iPr is shown in Scheme 1) [15] was tested for isomerization activity under standard conditions (5 mm 1 (1 mol %) and 0.5 m allylbenzene in CD 2 Cl 2 ;S cheme 1). [19][20][21][22] Thea ctivity of catalyst 2 is attributed to the hemilability of the ether ligand cis to the hydride ligand. Hypothesizing that the chloride ligand was blocking olefin binding adjacent to the hydride ligand, we turned to the cationic hydride [k 5 -( 15c5 NCOP iPr )Ir(H)] + (2)w ith [BAr F 4 ] À as the anion, which features apentadentate binding mode and ahemilabile ether donor (Scheme 1).…”

mentioning

confidence: 99%

“…[19][20][21][22] Thea ctivity of catalyst 2 is attributed to the hemilability of the ether ligand cis to the hydride ligand. [4,5,19,26,27] Detailed kinetic studies were carried out to provide insight into the mechanism of this cation-tuned catalysis. [23] We next sought to tune the activity of 2 using cationcrown interactions to adjust substrate-binding tendencies (Scheme 1).…”

mentioning

confidence: 99%

See 1 more Smart Citation

An Ion‐Responsive Pincer‐Crown Ether Catalyst System for Rapid and Switchable Olefin Isomerization

Kita

Miller

2017

Angewandte Chemie

View full text Add to dashboard Cite

Rapid, selective,a nd highly controllable iridiumcatalyzeda llylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with am acrocyclic "pincer-crown ether" ligand. An inactive chloride-ligated complex can be activated by halide abstraction with sodium salts,w ith the resulting catalyst [k 5 -( 15c5 NCOP iPr )Ir(H)] + exhibiting modest activity.A ddition of Li + provides af urther boost in activity,w ith up to 1000-fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity,l eading to three distinct catalyst states with activity spanning several orders of magnitude.M echanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: http://dx.

show abstract

Isomerization of Allylbenzenes

Cited by 256 publications

References 978 publications

Positionelle und geometrische Isomerisierung von Alkenen: der Gipfel der Atomökonomie

Positionelle und geometrische Isomerisierung von Alkenen: der Gipfel der Atomökonomie

Ru-Catalyzed Estragole Isomerization under Homogeneous and Ionic Liquid Biphasic Conditions

An Ion‐Responsive Pincer‐Crown Ether Catalyst System for Rapid and Switchable Olefin Isomerization

Contact Info

Product

Resources

About