Neue Synthesen und Reaktionen von Phosphetaniumsalzen mit planarem Gerüst

Brauer, David J.; Ciccu, A.; Hessler, G.; Stelzer, O.

doi:10.1002/cber.19921250904

Cited by 18 publications

(12 citation statements)

References 51 publications

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“…We synthesized several differently substituted phosphetane oxides 4 and employed them with a catalyst loading of 1.0 mol % in the model reaction. The penta-methyl substituted ring structure was chosen due to synthetic availability and the lability of unprotected phosphetane derivates under basic conditions . When the methyl-substituted catalyst 4a was employed, a yield of 46% of the desired product 3a with a good E / Z selectivity of 91:9 was achieved (Table , entry 1).…”

Section: Resultsmentioning

confidence: 99%

“…The penta-methyl substituted ring structure was chosen due to synthetic availability and the lability of unprotected phosphetane derivates under basic conditions. 36 When the methyl-substituted catalyst 4a was employed, a yield of 46% of the desired product 3a with a good E/Z selectivity of 91:9 was achieved (Table 1, entry 1). It is noteworthy that the chemoselectivities of the reaction with all catalysts at room temperature were very high (>95%), and lower yields were only achieved due to poor conversion.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Phosphetane Oxides as Redox Cycling Catalysts in the Catalytic Wittig Reaction at Room Temperature

2019

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Recently, phosphorus redox cycling has gained significant importance for a number of transformations originally requiring the use of stoichiometric amounts of phosphorus reagents. While these methodologies have several benefits, high catalyst loadings (≥10 mol %) and harsh reaction conditions (T ≥ 100 °C) often limit their versatility and applicability. Herein, we report differently substituted phosphetane oxides as efficient catalysts for the catalytic Wittig reaction. The phosphetane scaffold is easy to modify, and a number of catalysts can be obtained in a simple two-step synthesis. The activity in the Wittig reaction significantly surpasses previously reported phospholane-based catalysts and the reaction can be conducted with catalyst loadings as low as 1.0 mol % even at room temperature. Furthermore, a Brønsted acid additive is no longer required to achieve high yields at these mild conditions. A methyl-substituted phosphetane oxide was employed to synthesize 25 different alkenes with yields of up to 97%. The methodology has a good functional group tolerance and the reaction can be performed starting with alkyl chlorides, bromides, or iodides. Additionally, it was possible to use poly(methylhydrosiloxane) as the terminal reductant in the catalytic Wittig reaction employing 2-MeTHF as a renewable solvent. The intermediates of the Wittig reaction were analyzed by 31P NMR spectroscopy, and in situ NMR experiments confirmed phosphane oxide as the resting state of the catalyst. Further kinetic investigations revealed a striking influence of the base on the rate of phosphane oxide reduction.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Phosphetane Oxides as Redox Cycling Catalysts in the Catalytic Wittig Reaction at Room Temperature

2019

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“…Dichloromethane was distilled from CaH 2 under nitrogen prior to use. Ph 2 P(methallyl),14a Cy 2 P(allyl),21 Grubbs II catalyst22 and MePPh 3 ⋅I23 were prepared according to the reported methods. (η 5 ‐Vinylcyclopentadienyl)manganese(I) tricarbonyl ( 3w ),17a (η 5 ‐allylcyclopentadienyl)manganese(I) tricarbonyl ( 3x )17b and bromocymantrene ( 4n )16 were prepared by reported procedures.…”

Section: Methodsmentioning

confidence: 99%

A Continuous Flow Strategy for the Coupled Transfer Hydrogenation and Etherification of 5‐(Hydroxymethyl)furfural using Lewis Acid Zeolites

et al. 2014

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Hf-, Zr- and Sn-Beta zeolites effectively catalyze the coupled transfer hydrogenation and etherification of 5-(hydroxymethyl)furfural with primary and secondary alcohols into 2,5-bis(alkoxymethyl)furans, thus making it possible to generate renewable fuel additives without the use of external hydrogen sources or precious metals. Continuous flow experiments reveal nonuniform changes in the relative deactivation rates of the transfer hydrogenation and etherification reactions, which impact the observed product distribution over time. We found that the catalysts undergo a drastic deactivation for the etherification step while maintaining catalytic activity for the transfer hydrogenation step. (119) Sn and (29) Si magic angle spinning (MAS) NMR studies show that this deactivation can be attributed to changes in the local environment of the metal sites. Additional insights were gained by studying effects of various alcohols and water concentration on the catalytic reactivity.

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“…These reactions are potentially extendable to enantioselective processes givingp lanar-chiralc omplexes,a nd these studies are underway in our laboratories. 4 .T etrahydrofuran and benzene were distilledf rom benzophenone-ketyl under nitrogen prior to use.D ichloromethane was distilled from CaH 2 under nitrogen prior to use.P h 2 P(methallyl), [14a] Cy 2 P(allyl), [21] Grubbs II catalyst [22] and MePPh 3 ·I [23] were prepared according to the reportedm ethods. ( h 5 -Vinylcyclopentadienyl)manganese(I)t ricarbonyl( 3w),…”

Section: Discussionmentioning

confidence: 99%

Ring‐Closing Metathesis of (η⁵‐Alkenylcyclopentadienyl)(alkenylphosphine)manganese(I) Dicarbonyl Complexes

Tseng

Kamikawa

et al. 2015

Adv Synth Catal

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-(w-alkenyl)cyclopentadienyl](w-alkenylphosphine)manganese(I) dicarbonyl complexes were examined.T he RCM reactionb etween an h 5 -allyl-or an h 5 -vinyl-cyclopentadienyll iganda nd an allyldiphenylphosphine ligand in the manganese coordination spheresg ave the corresponding cyclized products in good to excellent yields.T he X-ray analyses of the two cyclized productsr evealed the structural differences between the C 3 -a nd the C 4 -bridged complexes.T he RCM reactions of the o-bromo-substituted manganese complexesw ere also operative andt he cyclized products were obtainedinexcellent yields of > 95%. Thepreferential formation of the C 4 -bridged species over the C 3 -bridged analogues in the RCM of the manganese complexes was confirmed by an intramolecular competitiveR CM experiment with the [h 5 -1-(methallyl)-2-(2-propenyl)cyclopentadienyl](allyldiphenylphosphine)manganese(I) dicarbonyl complex.

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Neue Synthesen und Reaktionen von Phosphetaniumsalzen mit planarem Gerüst

Cited by 18 publications

References 51 publications

Phosphetane Oxides as Redox Cycling Catalysts in the Catalytic Wittig Reaction at Room Temperature

Phosphetane Oxides as Redox Cycling Catalysts in the Catalytic Wittig Reaction at Room Temperature

A Continuous Flow Strategy for the Coupled Transfer Hydrogenation and Etherification of 5‐(Hydroxymethyl)furfural using Lewis Acid Zeolites

Ring‐Closing Metathesis of (η⁵‐Alkenylcyclopentadienyl)(alkenylphosphine)manganese(I) Dicarbonyl Complexes

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Neue Synthesen und Reaktionen von Phosphetaniumsalzen mit planarem Gerüst

Cited by 18 publications

References 51 publications

Phosphetane Oxides as Redox Cycling Catalysts in the Catalytic Wittig Reaction at Room Temperature

Phosphetane Oxides as Redox Cycling Catalysts in the Catalytic Wittig Reaction at Room Temperature

A Continuous Flow Strategy for the Coupled Transfer Hydrogenation and Etherification of 5‐(Hydroxymethyl)furfural using Lewis Acid Zeolites

Ring‐Closing Metathesis of (η5‐Alkenylcyclopentadienyl)(alkenylphosphine)manganese(I) Dicarbonyl Complexes

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Ring‐Closing Metathesis of (η⁵‐Alkenylcyclopentadienyl)(alkenylphosphine)manganese(I) Dicarbonyl Complexes