Cyclisation of citronellal over heterogeneous inorganic fluorides—highly chemo- and diastereoselective catalysts for (±)-isopulegol

Coman, Simona M.; Patil, Pratap T.; Wuttke, Stefan; Kemnitz, Erhard

doi:10.1039/b817572a

Cited by 47 publications

(53 citation statements)

References 17 publications

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“…In another study, even though not explicitly mentioned as synergy, a similar observation was made for the same intramolecular Prins reaction. By varying the F/OH ratio during synthesis of nanoscopic magnesium fluorides, unexpected catalytic properties were obtained in the Prins cyclisation of citronellal 51. 52 In that study it was also spectroscopically proven that the different combinations and variable strength of Lewis and Brønsted acid sites are responsible for increased activity.…”

Section: Resultsmentioning

confidence: 95%

On the Synergistic Catalytic Properties of Bimetallic Mesoporous Materials Containing Aluminum and Zirconium: The Prins Cyclisation of Citronellal

Telalović

Ramanathan

et al. 2011

Chemistry A European J

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Bimetallic three-dimensional amorphous mesoporous materials, Al-Zr-TUD-1 materials, were synthesised by using a surfactant-free, one-pot procedure employing triethanolamine (TEA) as a complexing reagent. The amount of aluminium and zirconium was varied in order to study the effect of these metals on the Brønsted and Lewis acidity, as well as on the resulting catalytic activity of the material. The materials were characterised by various techniques, including elemental analysis, X-ray diffraction, high-resolution TEM, N2 physisorption, temperature-programmed desorption (TPD) of NH3, and 27Al MAS NMR, XPS and FT-IR spectroscopy using pyridine and CO as probe molecules. Al-Zr-TUD-1 materials are mesoporous with surface areas ranging from 700–900 m2 g−1, an average pore size of around 4 nm and a pore volume of around 0.70 cm3 g−1. The synthesised Al-Zr-TUD-1 materials were tested as catalyst materials in the Lewis acid catalysed Meerwein–Ponndorf–Verley reduction of 4-tert-butylcyclohexanone, the intermolecular Prins synthesis of nopol and in the intramolecular Prins cyclisation of citronellal. Although Al-Zr-TUD-1 catalysts possess a lower amount of acid sites than their monometallic counterparts, according to TPD of NH3, these materials outperformed those of the monometallic Al-TUD-1 as well as Zr-TUD-1 in the Prins cyclisation of citronellal. This proves the existence of synergistic properties of Al-Zr-TUD-1. Due to the intramolecular nature of the Prins cyclisation of citronellal, the hydrophilic surface of the catalyst as well as the presence of both Brønsted and Lewis acid sites synergy could be obtained with bimetallic Al-Zr-TUD-1. Besides spectroscopic investigation of the active sites of the catalyst material a thorough testing of the catalyst in different types of reactions is crucial in identifying its specific active sites.

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Section: Resultsmentioning

confidence: 95%

On the Synergistic Catalytic Properties of Bimetallic Mesoporous Materials Containing Aluminum and Zirconium: The Prins Cyclisation of Citronellal

Telalović

Ramanathan

et al. 2011

Chemistry A European J

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“…On the other hand, the Lewis acidity of HS-MgF 2 is too weak to provide sufficient activity [10]. To overcome this problem, ternary fluorides were synthesised.…”

Section: Introductionmentioning

confidence: 99%

Sol–gel prepared nanoscopic metal fluorides – a new class of tunable acid–base catalysts

et al. 2010

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In this article, the high potential of the fluorolytic sol-gel process to synthesise nanoscopic metal fluorides with different acid-base properties is shown. These nanoscopic materials exhibit high potential to be used as heterogeneous catalysts due to their high surface areas and their tunable surface properties. Thus, for each specific reaction the required surface properties of the catalysts can be "adjusted" to achieve a high yield and selectivity of the desired product. As a consequence, a greener method of chemical production can be accomplished. Moreover the cheap and easy synthesis of the catalysts using basic chemicals makes them not only interesting for fundamental research but provides an easy transformation to industrial applications.

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“…The compound HSAlF 3 , although as described above is a strong Lewis acid, can exhibit some Brønsted acidity as a result of surface hydrolysis [59,60]. This compound and a range of AlF 3Àx (OH) x and MgF 2Àx (OH) x resulting from water introduced at the sol-gel step, are effective laboratory catalysts for batch conversion of citronellal to (AE)-isopulegol (the major product) and (AE)-neo-isopulegol [63]. The best activity and selectivity were found using catalysts that have very strong Lewis acid sites coupled with weak Brønsted acidity.…”

Section: High Surface Area (Hs) Magnesium Fluoridesmentioning

confidence: 97%

Investigating acidity of metal fluoride surfaces by spectroscopic and chemical methods

Winfield

2009

Journal of Fluorine Chemistry

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Cyclisation of citronellal over heterogeneous inorganic fluorides—highly chemo- and diastereoselective catalysts for (±)-isopulegol

Cited by 47 publications

References 17 publications

On the Synergistic Catalytic Properties of Bimetallic Mesoporous Materials Containing Aluminum and Zirconium: The Prins Cyclisation of Citronellal

On the Synergistic Catalytic Properties of Bimetallic Mesoporous Materials Containing Aluminum and Zirconium: The Prins Cyclisation of Citronellal

Sol–gel prepared nanoscopic metal fluorides – a new class of tunable acid–base catalysts

Investigating acidity of metal fluoride surfaces by spectroscopic and chemical methods

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