- Fe-Modified Zeolite BETA as an Active Catalyst for Intramolecular Prins Cyclization of Citronellal
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Abstract: Prins intramolecular cyclization of citronellal giving desired product isopulegol was performed using different modified zeolites BETA (Si/Al ratio 25, 38 and 75 modified with iron or zinc of 1, 5 or 10?wt.% by wet impregnation method). In case of materials BETA Si/Al 38 and 75 led material impregnation with metal to increase of material catalytic activity (accompanied with increase of amount of weak acid sites detected using temperature programmed desorption). Material BETA 38 with loading 1?wt.% of Fe provided 97% citronellal conversion and 94% selectivity of isopulegol formation (90?°C, toluene, 24?h). Graphic Abstract: [Figure not available: see fulltext.]
- Vrbková, Eva,Prejza, Tomá?,Lhotka, Miloslav,Vysko?ilová, Eli?ka,?erveny, Libor
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- Fluorocyclization of Unsaturated Aldehydes to Five- or Six-membered Cyclic Fluoroalcohols
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In the presence of HF-Et3N complexes, the stereoselective cyclization of 5- and 6-alkenals takes place to give five- and six-membered cyclic fluoroalcohols, respectively.
- Hayashi, Eiji,Hara, Shoji,Shirato, Hiroyasu,Hatekeyama, Tsuyoshi,Fukuhara, Tsuyoshi,Yoneda, Norihiko
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- Synthesis modulation as a tool to increase the catalytic activity of metal-organic frameworks: The unique case of UiO-66(Zr)
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The catalytic activity of the zirconium terephthalate UiO-66(Zr) can be drastically increased by using a modulation approach. The combined use of trifluoroacetic acid and HCl during the synthesis results in a highly crystalline material, with partial substitution of terephthalates by trifluoroacetate. Thermal activation of the material leads not only to dehydroxylation of the hexanuclear Zr cluster but also to post-synthetic removal of the trifluoroacetate groups, resulting in a more open framework with a large number of open sites. Consequently, the material is a highly active catalyst for several Lewis acid catalyzed reactions.
- Vermoortele, Frederik,Bueken, Bart,Le Bars, Gaelle,Van De Voorde, Ben,Vandichel, Matthias,Houthoofd, Kristof,Vimont, Alexandre,Daturi, Marco,Waroquier, Michel,Van Speybroeck, Veronique,Kirschhock, Christine,De Vos, Dirk E.
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- One-pot conversion of citronellal into isopulegol epoxide on mesoporous titanium silicate
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Citronellal was converted into isopulegol epoxide in a one-pot two-step reaction achieving a 68% global yield on Ti-MCM-41 and designing a two-solvent catalytic system.
- Guidotti,Moretti,Psaro,Ravasio
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- Tuning the surface properties of novel ternary iron(iii) fluoride-based catalysts using the template effect of the matrix
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Sol-gel prepared ternary FeF3-MgF2 materials have become promising heterogeneous catalysts due to their porosity and surface Lewis/Bronsted acidity (bi-acidity). Despite the good catalytic performance, nanoscopic characterisations of this type of material are still missing and the key factors controlling the surface properties have not yet been identified, impeding both a better understanding and further development of ternary fluoride catalysts. In this study, we characterised the interaction between the bi-acidic component (FeF3) and the matrix (MgF2) on the nano-scale. For the first time, the formation pathway of FeF3-MgF2 was profiled and the template effect of MgF2 during the synthesis process was discovered. Based on these new insights two novel materials, FeF3-CaF2 and FeF3-SrF2, were established, revealing that with decreasing the atomic numbers (from Sr to Mg), the ternary fluorides exhibited increasing surface acidity and surface area but decreasing pore size. These systematic changes gave rise to a panel of catalysts with tuneable surface and bulk properties either by changing the matrix alkaline earth metal fluoride or by adjusting their ratios to Fe or both. The template effect of the alkaline earth metal fluoride matrix was identified as the most probable key factor determining the surface properties and further influencing the catalytic performance in ternary fluoride based catalysts, and paves the way to targeted design of next-generation catalysts with tunable properties. This journal is
- Guo, Ying,Lippitz, Andreas,Saftien, Paul,Unger, Wolfgang E. S.,Kemnitz, Erhard
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- Continuous synthesis of menthol from citronellal and citral over Ni-beta-zeolite-sepiolite composite catalyst
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One-pot continuous synthesis of menthols both from citronellal and citral was investigated over 5 wt% Ni supported on H-Beta-38-sepiolite composite catalyst at 60–70 °C under 10–29 bar hydrogen pressure. A relatively high menthols yield of 53% and 49% and stereoselectivity to menthol of 71–76% and 72–74% were obtained from citronellal and citral respectively at the contact time 4.2 min, 70 °C and 20 bar. Citral conversion noticeably decreased with time-on-stream under 10 and 15 bar of hydrogen pressure accompanied by accumulation of citronellal, the primary hydrogenation product of citral, practically not affecting selectivity to menthol. A substantial amount of defuctionalization products observed during citral conversion, especially at the beginning of the reaction (ca. 1 h), indicated that all intermediates could contribute to formation of menthanes. Ni/H-Beta-38-sepiolite composite material prepared by extrusion was characterized by TEM, SEM, XPS, XRD, ICP-OES, N2 physisorption and FTIR techniques to perceive the interrelation between the physico-chemical and catalytic properties.
- Er?nen, Kari,M?ki-Arvela, P?ivi,Martinez-Klimov, Mark,Muller, Joseph,Murzin, Dmitry Yu.,Peurla, Markus,Simakova, Irina,Vajglova, Zuzana
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- Method for preparing L-menthol by adopting modified homogeneous catalyst
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The invention discloses a method for preparing L-menthol by adopting a modified homogeneous catalyst. The method comprises the following steps: preparing a modified homogeneous catalyst, preparing isopulegol, preparing D, L-menthol, and preparing L-menthol; wherein a ligand is prepared from 2, 6-dimethylpyridine and a ketone compound by using the modified homogeneous catalyst, the ligand is reacted with alkyl aluminum to obtain an organic aluminum compound, and L-menthol is prepared by chemically inducing chiral resolution of D, L-menthol. According to the method, the organic aluminum compoundis used as the catalyst of the ring-closure reaction of citronellal, so that the yield of isopulegol is increased, the selectivity on product isopulegol is high, and the used organic aluminum catalyst is easy to synthesize, high in stereoselectivity to reaction and easy to crystallize and recover; D, L-menthol is split by a chemical induction method, the method is simple to operate, the reactionyield of each step is high, the reaction conditions are stable, the product cannot be partially racemized, and the product loss is small.
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Paragraph 0038-0040; 0059-0066
(2020/03/09)
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- Sulfonated Hyper-cross-linked Porous Polyacetylene Networks as Versatile Heterogeneous Acid Catalysts
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Two highly sulfonated micro/mesoporous polymers, P(1,3-DEB)-SO3H and P(1,4-DEB)-SO3H, with permanent porosity, the specific surface area about 550 m2 ? g?1 and the content of SO3H groups of 2.7 mmol ? g?1 were prepared as new acid Porous Polymer Catalysts, PPCs. The PPCs were achieved by easy sulfonation of parent hyper-cross-linked micro/mesoporous polyacetylene-type networks resulting from a chain-growth homopolymerization of 1,3- and 1,4-diethynylbenzenes. New PPCs are reported as highly active and reusable heterogeneous catalysts of esterification of fatty acids with methanol and ethanol, Prins cyclization of aldehydes with isoprenol and intramolecular Prins cyclization of citronellal to isopulegol. The catalytic activity of the micro/mesoporous PPCs (TON values up to 522 mol ? mol?1) was higher than that of commercial polymer-based heterogeneous catalyst Amberlyst 15 possessing gel texture without permanent pores and that of p-toluenesulfonic acid applied as a homogeneous catalyst.
- Sekerová, Lada,B?ezinová, Pavlína,Do, Thuy Tran,Vysko?ilová, Eli?ka,Krupka, Ji?í,?erveny, Libor,Havelková, Lucie,Bashta, Bogdana,Sedlá?ek, Jan
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p. 1075 - 1084
(2020/01/03)
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- Synthesis of: P-menthane-3,8-diol from citronellal over lignin-derived carbon acid catalysts
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p-Menthane-3,8-diol (PMD) is receiving growing attention as a natural mosquito repellent with lower toxicity compared to the widely-used N,N-diethyl m-toluamide (DEET). In this study, sustainable carbon acid catalysts derived from alkaline lignin (AL) were prepared for synthesizing PMD from a popular chemical (±)-citronellal in an environmentally friendly solvent of water. The catalytic performances of the AL-derived carbon acid catalysts prepared at different pyrolysis temperatures were better than those of other catalysts such as carbon black and H-USY. In particular, when the AL pyrolyzed at 500 °C was used as the carbon acid catalyst, the conversion of (±)-citronellal was as high as 97% with a high PMD yield of 86%, indicating that waste alkaline lignin from pulp and paper industries can be used as a source of acid catalysts. It is found that the formation of PMD is preferred over catalysts with weaker acid sites, whereas isopulegol was more easily formed over stronger acid sites. Moreover, the reaction route of the citronellal cyclization-hydration reaction was more dominant via the carbocation-hydration pathway rather than the isopulegol hydration route on the weaker carbon acid catalyst. This journal is
- Abudula, Abuliti,Chaihad, Nichaboon,Du, Xiao,Guan, Guoqing,Hao, Xiaogang,Kurnia, Irwan,Li, Shasha,Prakoso, Tirto,Yoshida, Akihiro
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supporting information
p. 10441 - 10447
(2020/07/14)
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- Continuous flow synthesis of menthol: Via tandem cyclisation-hydrogenation of citronellal catalysed by scrap catalytic converters
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A continuous flow synthesis of menthol starting from citronellal catalysed by scrap catalytic converters is reported. The reaction was conducted in a tandem system connecting in series two catalytic systems, with the first having Lewis acid properties (favouring the cyclisation of citronellal to isopulegols) and the second having hydrogenation catalytic activity (catalysing the hydrogenation of isopulegols to menthols). A Lewis acid catalyst was prepared by supporting iron oxide nanoparticles over a waste material, i.e. the ceramic core of scrap catalytic converters (SCATs) via a microwave assisted method. Most importantly, SCATs, containing a low residual noble metal content, could be directly employed in the second step as hydrogenation catalysts. The reaction was performed studying the influence on the yield and selectivity to (-)-menthol of various reaction parameters (T, p and flow rate). Under the best reaction conditions (at a flow rate of 0.1 mL min-1 and at 373 K and 413 K for cyclisation and hydrogenation steps respectively) a conversion of >99% of (+)-citronellal to (-)-menthol with 77% final yield was achieved.
- Zuliani, Alessio,Cova, Camilla Maria,Manno, Roberta,Sebastian, Victor,Romero, Antonio A.,Luque, Rafael
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p. 379 - 387
(2020/02/13)
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- Unveiling reactive metal sites in a Pd pincer MOF: Insights into Lewis acid and pore selective catalysis
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A porous Zr metal-organic framework, 1-PdBF4 [Zr6O4(OH)4(OAc)2.4{(PNNNP)Pd(MeCN)}2.4(BF4)2.4; PNNNP = 2,6-(HNPAr2)2C5H3N; Ar = p-C6H4CO2-], has been synthesized via postsynthetic oxidative I-/BF4- ligand exchange using NOBF4. 1-PdBF4 enjoys markedly superior catalytic activity and recyclability to its trifluoracetate-exchanged analogue, 1-PdTFA, for the intramolecular cyclization of o-alkynyl anilines and the carbonyl-ene cyclization of citronellal. Moreover, 1-PdBF4 demonstrates a rare example of pore selective catalysis for the cyclization of 2-ethynyl aniline.
- Reiner, Benjamin R.,Kassie, Abebu A.,Wade, Casey R.
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supporting information
p. 9588 - 9595
(2019/07/09)
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- Nb-doped variants of high surface aluminium fluoride: A very strong bi-acidic solid catalyst
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A niobium doped high surface aluminium fluoride (HS-AlF3) catalyst was prepared, using an approach in which niobium doped aluminium hydroxide fluoride obtained via reaction of aqueous HF with the respective metal alkoxides in isopropanol is further fluorinated under flow of CHClF2 at 200 °C. A comparable procedure was used to synthesize a Nb-free variant for comparison. Both catalysts exhibit very strong Lewis acidic surface sites which are capable to activate strong carbon-halogen bonds at room temperature, just as the classical high-surface AlF3 (HS-AlF3), obtained by reacting aluminium isopropoxide with anhydrous HF, does. The catalysts were characterized by elemental analysis, P-XRD, MAS NMR spectroscopy, N2 adsorption, NH3-TPD, and pyridine photoacoustic FT-IR spectroscopy. In contrast to previously reported niobium doped HS-AlF3, which was prepared using anhydrous HF, the doped catalyst obtained via this aqueous HF-route shows excellent performance both in the isomerization of 1,2-dibromohexafluoropropane, a reaction that occurs only in the presence of the strongest Lewis acids, and in the cyclization of citronellal to isopulegol, a reaction which requires both, Lewis and Br?nsted acid sites.
- Marshall, Clara Patricia,Scholz, Gudrun,Braun, Thomas,Kemnitz, Erhard
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p. 6834 - 6845
(2019/05/27)
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- Method for improving optical purity of L-isopulegol through chiral resolution
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The invention provides a method for improving the optical purity of L-isopulegol through chiral resolution. The method comprises the following steps: putting D,L-isopulegol and a resolution agent L-linalool into a dispersant and an auxiliary agent and reacting for 3 to 4 hours at 70 to 80 DEG C; after cooling to 10 to 25 DEG C, centrifuging and separating to obtain an intermediate L-isopulegol.L-linalool; carrying out alkali analysis on the intermediate; decomposing the intermediate; then carrying out gel chromatography to obtain the high-purity L-isopulegol. The method has the advantages of low raw material cost and low reaction energy consumption and is applicable to large-scale industrialized production.
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- One-Pot Absolute Stereochemical Identification of Alcohols via Guanidinium Sulfate Crystallization
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A novel technique for the absolute stereochemical determination of alcohols has been developed that uses crystallization of guanidinium salts of organosulfates. The simple one-pot, two-step process leverages facile formation of guandinium organosulfate single crystals for the straightforward determination of the absolute stereochemistry of enantiopure alcohols by means of X-ray crystallography. The strong hydrogen bonding network drives the stability of the crystal lattice and allows for a diverse range of organic alcohol substrates to be analyzed.
- Brummel, Beau R.,Lee, Kinsey G.,McMillen, Colin D.,Kolis, Joseph W.,Whitehead, Daniel C.
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supporting information
p. 9622 - 9627
(2019/12/02)
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- Citronellal cyclisation over heteropoly acid supported on modified montmorillonite catalyst: effects of acidity and pore structure on catalytic activity
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Citronellal cyclisation to isopulegol is an important intermediate step in the production of menthol. Several heteropoly acids (PTA) supported on modified montmorillonite (MM) catalysts were synthesized and then tested in cyclisation reactions. The prepared samples were characterized by XRD, ICP-OES, FTIR, N2 sorption, NH3-TPD, pyridine adsorption, amine titration and FE-SEM techniques. Effects of post-treatment were studied on montmorillonite pore structure, acidity and catalytic activity. The catalytic activity and isopulegol selectivity improved with acid-treatment and PTA loading. The amount of Lewis acidity of montmorillonite was enhanced with acid-treatment and PTA impregnation. In cyclisation, highest catalytic activity (31.87?mmol?cat?g?1?min?1) was achieved with 96% isopulegol yield in the use of 20% PTA-MM catalyst. The highest catalytic activity and selectivity were obtained in the presence of higher acidity and strong Lewis acidic sites, whereas effects of pore structure blockage seemed minor. The catalytic activity further decreased with the loss of active acidic sites (L and B) due to PTA decomposition with calcination at a higher temperature.
- Shah, Abdul Karim,Park, Sungsoo,Khan, Hassnain Abbas,Bhatti, Umair Hassan,Kumar, Praveen,Bhutto, Abdul Waheed,Park, Yeung Ho
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p. 2405 - 2423
(2018/03/21)
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- Preparation method of isopulegol
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The invention belongs to the technical field of chemistry and chemical engineering, and relates to a preparation method of isopulegol. The preparation method is characterized in that citronellal is used as raw materials; under the catalysis of anhydrous zinc bromide, a proper quantity of calixarene is added as a cocatalyst; cyclization reaction is performed to generate the isopulegol; zinc bromidecatalyst containing wastewater generated after the quenching reaction of 0.05mol/l of hydrobromic acid water solution is subjected to azeotropic dehydration to prepare anhydrous zinc bromide again tobe applied to cyclization reaction. The method has the advantages that the cyclization efficiency is greatly improved; meanwhile, wastewater and waste salt are greatly reduced; the green synthesis ofthe isopulegol is realized. The operation is simple and convenient; the process design is ingenious; the environment pollution is low; the preparation method is suitable for industrial production.
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Paragraph 0033; 0035; 0037; 0039; 0041; 0043; 0047; 0049
(2018/09/21)
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- Method of preparing isopulegol from citronellal and method of recycling catalyst therein
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The invention provides a method of preparing isopulegol from citronellal and a method of recycling a catalyst therein. Citronellal is used as an initial material to prepare isopulegol under the catalytic action of a binaphthol-based aluminum compound via cyclization; a high-boiling-point solvent is used to recycle the catalyst. The binaphthol-based aluminum compound is used as the catalyst; the conditions are milder; reaction enantioselectivity is 95-99.9%, and the conversion rate is up to 95-99.9%. The method of recycling the catalyst is simple; the recycled catalyst is directly usable, and no regeneration is required; the methods are particularly suitable for industrial production.
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Page/Page column 9-14
(2018/08/28)
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- "naked" Lithium Cation: Strongly Activated Metal Cations Facilitated by Carborane Anions
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Experimental and spectroscopic studies revealed unprecedented reactivity of a "naked" lithium cation with very weakly coordinating anions, including carborane anions. The superactivated lithium cation has greatly enhanced Lewis acidic character and mediates various organic reactions such as carbonyl-ene reaction, NBS-bromination of unactivated aromatics, and Friedel-Crafts alkylation, which are not promoted by conventional lithium salts. Chemical robustness of the counteranion also plays an important role in the chemistry of the strongly activated lithium cation.
- Kitazawa, Yu,Takita, Ryo,Yoshida, Kengo,Muranaka, Atsuya,Matsubara, Seijiro,Uchiyama, Masanobu
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p. 1931 - 1935
(2017/02/26)
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- Synthesis, characterization and performance of bifunctional catalysts for the synthesis of menthol from citronellal
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The synthesis of a series of bifunctional catalysts (1 wt% Pt/W-TUD-1 (Technische Universiteit Delft-1) and 1 wt% Pt/WO3/TUD-1) with different tungsten loadings (5-30 wt% WO3) is described. They were characterized using ICP-OES, INAA, N2 physisorption, XRD and TEM. Their catalytic performance (activity and selectivity) was evaluated in the two-step catalytic synthesis of menthol from citronellal using kinetic analysis. Introducing tungsten during the TUD-1 synthesis results in a high WO3 dispersion, essential for the acidity of the catalyst. High tungsten dispersion is also critical for the Pt hydrogenation activity. Therefore, high dispersion combined with optimal tungsten loading resulted in the highest catalytic activity. The best performing catalyst was 1 wt% Pt/W-TUD-1 (silicon to tungsten ratio of 30), with the highest yields of menthol (96%).
- Ten Dam,Ramanathan,Djanashvili,Kapteijn,Hanefeld
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p. 12041 - 12053
(2017/03/08)
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- A by citronellal method for preparing Isopulegol (by machine translation)
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The invention discloses a method for preparing Isopulegol citronellal, benzenes sulfonic acid in the presence of a compound nozzle of citronellal cyclized for preparing Isopulegol, benzenes sulfonic acid aluminum compound is passing type (I) benzenes sulfonic acid of the formula (II) ligand of aluminized compound and/or a formula (III) prepared of aluminized compound; (R1 )3 - p AIHp (II), MAIH4 (III), the states the cyclization of mild reaction conditions, the reaction temperature is preferably 5 - 15 °C, reaction enantioselectivity is 90% - 99%, conversion rate may reach 80 - 99.9%. (by machine translation)
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Paragraph 0134-0142
(2017/10/10)
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- Metal Nanoparticles Supported on Perfluorinated Superacid Polymers: A Family of Bifunctional Catalysts for the Selective, One-Pot Conversion of Vegetable Substrates in Water
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We describe the rational design of a new versatile family of bifunctional catalytic materials based on the combination of supported metal nanoparticles (Pd, Rh, Ru) and the superacid, perfluorinated Aquivion PFSA polymer. The heterogeneous catalysts were tested in the multi-step valorisation of representative plant derivatives to high-added-value chemicals. Particularly, the conversion of (+)-citronellal to (-)-menthol and levulinic acid to γ-valerolactone was achieved in one pot and in one stage in the water phase and shows full selectivity at a high conversion level under mild reaction conditions. The results are discussed in terms of the catalyst micro-structure.
- Moreno-Marrodan, Carmen,Liguori, Francesca,Barbaro, Pierluigi,Caporali, Stefano,Merlo, Luca,Oldani, Claudio
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p. 4256 - 4267
(2017/10/12)
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- Selectivity in the Cyclization of Citronellal Introduced by Squalene Hopene Cyclase Variants
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The squalene hopene cyclase from Alicyclobacillus acidocaldarius (AacSHC) is a highly efficient enzyme catalyst for stereoselective Br?nsted acid catalysis. We engineered AacSHC to catalyze the selective Prins cyclization of citronellal. Four active site variants were identified for the diastereoselective cyclization of (S)-citronellal to stereoisomers (?)-iso-isopulegol, (+)-isopulegol and (?)-neo-isopulegol, respectively. The replacement of active site residues resulted in two triple variants that catalyzed the transformation of (R)-citronellal to give the isomers (+)-neo-isopulegol and (?)-isopulegol with up to >99 % de, respectively. The newly designed library of functionally diverse active site geometries exhibits high selective control during citronellal cyclization, leading exclusively to a single diastereomer of the desired isopulegol. Whereas the cyclization of citronellal with chemical catalysts was observed to produce the isopulegol isomer with the lowest energy, the reaction with AacSHC variants proceeded with higher product selectivity. The results of this study show that variants of AacSHC are excellent catalysts for the highly selective formation of isopulegol stereoisomers.
- Bastian, Silke A.,Hammer, Stephan C.,Kre?, Nico,Nestl, Bettina M.,Hauer, Bernhard
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p. 4364 - 4368
(2017/11/16)
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- General, Auxiliary-Enabled Photoinduced Pd-Catalyzed Remote Desaturation of Aliphatic Alcohols
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A general, efficient, and site-selective visible light-induced Pd-catalyzed remote desaturation of aliphatic alcohols into valuable allylic, homoallylic, and bis-homoallylic alcohols has been developed. This transformation operates via a hybrid Pd-radical mechanism, which synergistically combines the favorable features of radical approaches, such as a facile remote C-H HAT step, with that of transition-metal-catalyzed chemistry (selective β-hydrogen elimination step). This allows achieving superior degrees of regioselectivity and yields in the desaturation of alcohols compared to those obtained by the state-of-the-art desaturation methods. The HAT at unactivated C(sp3)-H sites is enabled by the easily installable/removable Si-auxiliaries. Formation of the key hybrid alkyl Pd-radical intermediates is efficiently induced by visible light from alkyl iodides and Pd(0) complexes. Notably, this method requires no exogenous photosensitizers or external oxidants.
- Parasram, Marvin,Chuentragool, Padon,Wang, Yang,Shi, Yi,Gevorgyan, Vladimir
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supporting information
p. 14857 - 14860
(2017/10/31)
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- Flow Pickering Emulsion Interfaces Enhance Catalysis Efficiency and Selectivity for Cyclization of Citronellal
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Cyclization of citronellal is a necessary intermediate step to produce the important flavor chemical (?)-menthol. Here, a continuous-flow Pickering emulsion (FPE) strategy for selective cyclization of citronellal to (?)-isopulegol by using water droplets hosting a heteropolyacid (HPA) catalyst to fill a column reactor is demonstrated. Owing to the large liquid–liquid interface and the excellent confinement ability of droplets toward HPA, the FPE system exhibited a much higher catalysis efficiency than its batch counterpart (2–5-fold) and an excellent durability (two months). Moreover, a remarkably enhanced selectivity was observed from 34.8 % for batch reactions to 64 % for the FPE reactions. It was found that the water droplet size and the flow rate significantly impact the catalysis selectivity and efficiency. This study not only represents an unprecedented and sustainable process for the selective cyclization of citronellal but also demonstrates a new flow-interface catalysis effect that can be useful for designing innovative catalysis systems in the future.
- Chen, Huan,Zou, Houbing,Hao, Yajuan,Yang, Hengquan
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p. 1989 - 1995
(2017/05/16)
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- Organocatalyzed intramolecular carbonyl-ene reactions
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An organocatalyzed intramolecular carbonyl-ene reaction was developed to produce carbocyclic and heterocyclic 5- and 6-membered rings from a citronellal-derived trifluoroketone and a variety of aldehydes. A phosphoramide derivative was found to promote the cyclization of the trifluoroketone, whereas a less acidic phosphoric acid proved to be a superior catalyst for the aldehyde substrates.
- Dahlmann, Heidi A.,McKinney, Amanda J.,Santos, Maria P.,Davis, Lindsey O.
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- Insights into the Complexity of Heterogeneous Liquid-Phase Catalysis: Case Study on the Cyclization of Citronellal
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Heterogeneously catalyzed liquid-phase reactions are highly complex chemical systems. As the local molecular composition close to the active site is often unknown, sophisticated spectroscopic tools are needed to gain insights on a molecular level. One solution to these challenges is the use of modulation excitation spectroscopy with attenuated total reflection infrared spectroscopy. We use this highly sensitive and selective technique to study the Lewis acid-catalyzed cyclization of citronellal over mesoporous Sn-SBA-15 and microporous Sn-Beta. We find that the reaction mechanism is generally similar for the two materials. However, the confined space at the active site within the zeolite stabilizes the coordination of citronellal to the SnIV site and prevents byproduct formation, as well as the reverse reaction due to size-exclusion of the product isopulegol. The use of the Lewis base acetonitrile as solvent reduces the catalytic performance with Sn-SBA-15 drastically, while Sn-Beta remains highly active. Infrared spectra reveal a simultaneous coordination of citronellal and acetonitrile to the tin site in Sn-Beta, whereas in Sn-SBA-15, the more-accessible SnIV site leads to much stronger and hence detrimental competitive adsorption. The results obtained in this study indicate that the substrate-catalyst-solvent combination needs to be optimized in order to maximize the performance of solid-liquid reactions.
- Müller, Philipp,Wolf, Patrick,Hermans, Ive
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p. 2760 - 2769
(2016/07/06)
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- Synthesis of bimetallic Zr(Ti)-naphthalendicarboxylate MOFs and their properties as Lewis acid catalysis
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Bimetallic Zr(Ti)-NDC based metal-organic frameworks (MOFs) have been prepared by incorporation of titanium(iv) into zirconium(iv)-NDC-MOFs (UiO family). The resulting materials maintain thermal (up to 500 °C), chemical and structural stability with respect to parent Zr-MOFs as can be deduced from XRD, N2 adsorption, FTIR and thermal analysis. The materials have been studied in Lewis acid catalyzed reactions, such as, domino Meerwein-Ponndorf-Verley (MPV) reduction-etherification of p-methoxybenzaldehyde with butanol, isomerization of α-pinene oxide and cyclization of citronellal.
- Rasero-Almansa, Antonia M.,Iglesias, Marta,Sánchez, Félix
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p. 106790 - 106797
(2016/11/23)
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- The effect of catalyst preparation conditions on the synthesis of menthol from citronellal on Ru/H-BEA
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Heterogeneous Ru/H-BEA catalysts are suitable catalysts for the one-pot transformation of citronellal to menthols, which requires a combined cyclization-hydrogenation step. Here, we report the role of different preparation conditions-namely the choice of the Ru-precursor (Ru(NO)(NO3)3), Ru(acac)3, RuCl3 and Ru3(CO)12) as well as the reduction temperature (523-923 K) of the catalyst. Using Ru(NO)(NO3)3 as precursor the highest activity was obtained, while the product distribution was not strongly affected by the choice of the precursor. On the contrary the reduction temperature leads to very different product distributions: Increasing it from 623 K to 923 K for a 1%Ru/H-BEA-25 catalyst the competitive hydrogenation of citronellal was diminished, which leads to an increased selectivity to menthols from 77% to 87% and additional the activity increases with a factor of 3.4. This behaviour might be due to a dealumination of the zeolite during reduction at higher temperatures. Moreover, in combination with appropriate reaction conditions a yield to menthols of 92% can be reached.
- Pl??er, Jutta,Dedeaga, Fatma,Lucas, Martin,Claus, Peter
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p. 100 - 108
(2016/03/05)
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- The effect of host structure on the selectivity and mechanism of supramolecular catalysis of Prins cyclizations
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The effect of host structure on the selectivity and mechanism of intramolecular Prins reactions is evaluated using K12Ga4L6 tetrahedral catalysts. The host structure was varied by modifying the structure of the chelating moieties and the size of the aromatic spacers. While variation in chelator substituents was generally observed to affect changes in rate but not selectivity, changing the host spacer afforded differences in efficiency and product diastereoselectivity. An extremely high number of turnovers (up to 840) was observed. Maximum rate accelerations were measured to be on the order of 105, which numbers among the largest magnitudes of transition state stabilization measured with a synthetic host-catalyst. Host/guest size effects were observed to play an important role in host-mediated enantioselectivity.
- Hart-Cooper, William M.,Zhao, Chen,Triano, Rebecca M.,Yaghoubi, Parastou,Ozores, Haxel Lionel,Burford, Kristen N.,Toste, F. Dean,Bergman, Robert G.,Raymond, Kenneth N.
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p. 1383 - 1393
(2015/02/19)
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- ALUMINUM CATALYST
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An aluminum catalyst is obtained by reacting at least one compound of a specific alkylaluminum compound and a specific hydridoaluminum compound with a specific hydroxy compound. The specific hydroxyl compound is a specific 2-cycloalkyl-6-arylphenol or a specific di(2-cycloalkyl-6-arylphenol). A method for producing isopulegol or optically active isopulegol includes selectively cyclizing citronellal using the aluminum catalyst.
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Paragraph 0129-0131
(2015/11/27)
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- Highly selective menthol synthesis by one-pot transformation of citronellal using Ru/H-BEA catalysts
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The one-pot transformation of citronellal to menthol requires a combined cyclization-hydrogenation step for which Ru/H-BEA catalysts were identified as highly active and selective catalysts. After identifying zeolite H-BEA as the most promising heterogeneous catalyst for the cyclization of citronellal to the intermediate isopulegol, bifunctional metal/H-BEA catalysts were investigated in the one-pot transformation of citronellal to menthols. Using Pd undesired defunctionalization prevailed, while using Pt and Ru, the formation of menthols predominated. Finally, for Ru/H-BEA catalysts, the effect of catalyst composition (Si:Al ratio, Ru content) and reaction conditions (temperature, hydrogen pressure, and solvent) was investigated to diminish citronellal hydrogenation, dimerization, and defunctionalization. Accordingly, with a 1%Ru/H-BEA-25 catalyst (Ru particle size = 1 nm) in dioxane at 15 bar hydrogen pressure and 373 K, a very high selectivity to menthols of 93% at nearly full conversion was obtained. The catalyst is also highly diastereoselective producing 79% of the desired (±)-menthol.
- Pl?sser, Jutta,Lucas, Martin,Claus, Peter
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p. 189 - 197
(2015/03/31)
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- Highly selective menthol synthesis by one-pot transformation of citronellal using Ru/H-BEA catalysts
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The one-pot transformation of citronellal to menthol requires a combined cyclization-hydrogenation step for which Ru/H-BEA catalysts were identified as highly active and selective catalysts. After identifying zeolite H-BEA as the most promising heterogeneous catalyst for the cyclization of citronellal to the intermediate isopulegol, bifunctional metal/H-BEA catalysts were investigated in the one-pot transformation of citronellal to menthols. Using Pd undesired defunctionalization prevailed, while using Pt and Ru, the formation of menthols predominated. Finally, for Ru/H-BEA catalysts, the effect of catalyst composition (Si:Al ratio, Ru content) and reaction conditions (temperature, hydrogen pressure, and solvent) was investigated to diminish citronellal hydrogenation, dimerization, and defunctionalization. Accordingly, with a 1%Ru/H-BEA-25 catalyst (Ru particle size = 1 nm) in dioxane at 15 bar hydrogen pressure and 373 K, a very high selectivity to menthols of 93% at nearly full conversion was obtained. The catalyst is also highly diastereoselective producing 79% of the desired (±)-menthol.
- Pl?sser, Jutta,Lucas, Martin,Claus, Peter
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p. 189 - 197
(2015/09/28)
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- Highly selective aluminium-catalysed intramolecular Prins reaction for L-menthol synthesis
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An aluminium complex bearing 2-cyclohexyl-6-phenylphenol afforded (5R)-n-isopulegol from (R)-citronellal via the intermolecular Prins reaction with an exceptionally high diastereoselectivity. Using this reaction, l-menthol was obtained with an excellent diastereoselectivity.
- Itoh,Maeda,Yamada,Hori,Mino,Sakamoto, Masami
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p. 61619 - 61623
(2015/02/19)
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- Comparison of acidic site quantification methods for a series of nanoscopic aluminum hydroxide fluorides
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Quantitative determination of acidic surface sites is highly important for the characterization of solid acids because the activity of a catalyst is often related to the concentration of these sites. A recently developed method using 15N Nuclear Magnetic Resonance spectroscopy (NMR) for the quantification of acidic Lewis and Bronsted sites has been tested for a series of nanoscopic aluminum hydroxide fluorides. Comparison with other methods for the quantitative determination of acidic sites shows that this 15N NMR quantification method is a promising technique for the comprehensive investigation of acidic sites. Three different acidic sites, one Bronsted and two Lewis sites, can be distinguished by their 15N chemical shifts of pyridine and simultaneously quantified under conditions corresponding to catalytic reaction conditions. Determination of the individual concentrations of acidic sites allows further insight into the catalytic process. It was found that the concentration of Bronsted sites correlates with catalyzed conversion of citronellal to isopulegol in the investigated series of catalysts. Additionally, investigations indicate that one of the Lewis sites become blocked during the reaction of citronellal.
- Hemmann, Felix,Jaeger, Christian,Kemnitz, Erhard
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p. 56900 - 56909
(2015/01/08)
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- Superacidity in sulfated metal-organic framework-808
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Superacids, defined as acids with a Hammett acidity function H0 ≤ -12, are useful materials, but a need exists for new, designable solid state systems. Here, we report superacidity in a sulfated metal-organic framework (MOF) obtained by treating the microcrystalline form of MOF-808 [MOF-808-P: Zr6O5(OH)3- (BTC)2(HCOO)5(H2O)2, BTC = 1,3,5-benzenetricarboxylate] with aqueous sulfuric acid to generate its sulfated analogue, MOF-808-2.5SO4 [Zr6O5(OH)3(BTC)2- (SO4)2.5(H2O)2.5]. This material has a Hammett acidity function H0 ≤ -14.5 and is thus identified as a superacid, providing the first evidence for superacidity in MOFs. The superacidity is attributed to the presence of zirconiumbound sulfate groups structurally characterized using single-crystal X-ray diffraction analysis.
- Jiang, Juncong,Gándara, Felipe,Zhang, Yue-Biao,Na, Kyungsu,Yaghi, Omar M.,Klemperer, Walter G.
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supporting information
p. 12844 - 12847
(2015/12/26)
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- TiO2(SiO2)x and ZrO2(SiO 2)x cryogels as catalysts for the citronellal cyclization to isopulegol
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TiO2(SiO2)x and ZrO2(SiO 2)x mixed oxides prepared by a simple sol-gel procedure plus freeze-drying achieve very high surface areas. Such cryogels are shown to catalyze the cyclization of citronellal to isopulegol. The dispersion of the active metal has been optimized, as it is shown that high specific surface areas are the key for the catalytic activity of the cogels. Nevertheless zirconia-silica cryogels depict much higher catalytic activity, with only 5 mol% Zr being required, than the corresponding titania-silica mixed oxides.
- Jimeno, Ciril,Miras, Jonathan,Esquena, Jordi
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p. 616 - 623
(2013/07/19)
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- Sol-gel synthesis and characterisation of nanoscopic FeF3-MgF2 heterogeneous catalysts with bi-acidic properties
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Nanoscopic metal fluorides with surface hydroxy groups are of broad interest in heterogeneous catalysis. With both Lewis and Bronsted acid sites on the surface, these catalysts can be applied to a wide range of reactions. Having previously synthesised AlF3- and MgF2-based catalysts, we report a new transition metal fluoride with bi-acidity. A pre-dehydration procedure was developed to introduce hydroxy groups to a Lewis acid, FeF3. Subsequently, ternary nanoscopic FeF3-MgF2 with enhanced porosity was prepared through a one-step fluorination. The interaction between MgF2 and FeF3 was elucidated. Surface characterisation revealed a remarkable increase in the surface area of FeF3-MgF2 compared with FeF3. More importantly, medium-strong Lewis and Bronsted acid sites were detected on the FeF3-MgF2 surface. In line with its bi-acidity, FeF3-MgF2 was highly active in the model reaction, the isomerisation of citronellal to isopulegol. Finally, we discuss how the porosity and surface acidity jointly determine the activity of FeF3-MgF2. Our study demonstrates the feasibility of ternary FeF3-MgF2 and opens new possibilities to synthesise bi-acidic fluoride catalysts.
- Guo, Ying,Gaczynski, Piotr,Becker, Klaus-Dieter,Kemnitz, Erhard
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p. 2223 - 2232
(2013/08/23)
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- METHOD FOR MANUFACTURING OPTICALLY ACTIVE MENTHOL
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An object of the present invention is to provide a method for manufacturing an optically active menthol having fewer steps, which generates less environmentally polluting waste because a catalytic reaction is involved in all of the steps, and is capable of saving a production cost. The present invention relates to a method for manufacturing an optically active menthol, including the following steps: A-1) asymmetrically hydrogenating at least one of geranial and neral to thereby obtain an optically active citronellal, B-1) conducting a ring-closure reaction of the optically active citronellal in the presence of an acid catalyst to thereby obtain an optically active isopulegol, and C-1) hydrogenating the optically active isopulegol to thereby obtain an optically active menthol.
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Paragraph 0523
(2013/10/07)
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- B-TUD-1: A versatile mesoporous catalyst
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Novel amorphous mesoporous borosilicate, B-TUD-1, was prepared to test its performance for different sustainable reactions. The structure of the material, the effective incorporation of boron into the framework as well as the nature of incorporated boron were verified by N2-sorption, XRD, ICP-OES, TEM, NH3-desorption, MAS NMR and FTIR. The potential of these materials as catalysts was tested in two reactions under different conditions. They showed an apparently good activity and recycling potential for HMF (5-hydroxymethyl- furfural) synthesis. However leaching of boron occurred during this aqueous reaction. We could demonstrate that the leached boron was actually the catalyst of the reaction. In a second reaction, this time in organic solvent, the B-TUD-1 materials were tested for the Prins cyclisation of citronellal. A very promising activity was obtained. The catalyst could be recycled and no boron leached, as demonstrated by hot filtration experiments. The Royal Society of Chemistry 2013.
- Ranoux, Adeline,Djanashvili, Kristina,Arends, Isabel W.C.E.,Hanefeld, Ulf
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p. 21524 - 21534
(2013/11/06)
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- Selective monoterpene-like cyclization reactions achieved by water exclusion from reactive intermediates in a supramolecular catalyst
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A polyanionic supramolecular assembly (1) is shown to catalytically cyclize the monoterpene citronellal and two homologues. In contrast to cyclization in acidic aqueous solution, the hydrophobic interior of 1 prevents the capture of reactive intermediates by water. This effect was also observed in the gold-catalyzed cycloisomerization of an enyne. Due to the steric confinement of the catalyst's interior, Prins cyclizations in 1 proceed cleanly both for substrates containing and lacking gem-dimethyl substitution. Encapsulation in 1 consequently imposes a degree of mechanistic control that, similar to enzyme catalysis, is not observed in bulk aqueous solution.
- Hart-Cooper, William M.,Clary, Kristen N.,Toste, F. Dean,Bergman, Robert G.,Raymond, Kenneth N.
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p. 17873 - 17876
(2013/01/15)
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- Electronic effects of linker substitution on Lewis acid catalysis with metal-organic frameworks
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Functionalized linkers can greatly increase the activity of metal-organic framework (MOF) catalysts with coordinatively unsaturated sites. A clear linear free-energy relationship (LFER) was found between Hammett m values of the linker substituents X and the rate kX of a carbonyl-ene reaction. This is the first LFER ever observed for MOF catalysts. A 56-fold increase in rate was found when the substituent is a nitro group (see picture). Copyright
- Vermoortele, Frederik,Vandichel, Matthias,Van De Voorde, Ben,Ameloot, Rob,Waroquier, Michel,Van Speybroeck, Veronique,De Vos, Dirk E.
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supporting information; experimental part
p. 4887 - 4890
(2012/06/18)
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- ALUMINUM COMPLEX AND USE THEREOF
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Provided is a process in which cyclization of a compound having, in a molecule, a formyl group and a double bond which allow carbonyl-ene cyclization, the compound existing as a mixture of optical isomers thereof, increases the ratio of a particular optical isomer not only in a cyclized compound, but also in an unreacted compound. The process comprises performing, in the presence of a specified aluminum complex represented by the general formula: [Al2(L1)n (L2)3-n]m, cyclization of a compound having, in a molecule, a formyl group and a double bond which allow carbonyl-ene cyclization, the compound existing as a mixture of optical isomers thereof, to increase the ratio of a particular optical isomer.
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Page/Page column 13
(2011/02/25)
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- ORGANOALUMINUM COMPOUND
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A catalyst for obtaining isopulegol of high diastereoselectivity by highly selective cyclization reaction of citronellal is provided. The present invention relates to an organoaluminum compound obtained by reacting at least one organoaluminumoxy compound selected from the group consisting of chain aluminoxanes, cyclic aluminoxanes and bis(dialkylaluminumoxy)alkylboranes, with at least one hydroxy compound selected from the group consisting of diarylphenols, bis(diarylphenol) compounds, biaryldiols, dimethanols and silanols.
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Page/Page column 22
(2011/12/13)
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- Organoaluminium compounds and their use as catalysts in the selective cyclisation of citronellal to isopulegol
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A catalyst for obtaining isopulegol of high diastereoselectivity by highly selective cyclization reaction of citronellal is provided. The present invention relates to an organoaluminum compound obtained by reacting at least one organoaluminumoxy compound selected from the group consisting of chain aluminoxanes, cyclic aluminoxanes and bis(dialkylaluminumoxy)alkylboranes, with at least one hydroxy compound selected from the group consisting of diarylphenols, bis(diarylphenol) compounds, biaryldiols, dimethanols and silanols.
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- Synthesis of a key intermediate for the total synthesis of pseudopteroxazole
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A facile synthesis of a key intermediate for the total synthesis of anti-mycobacterial compound pseudopteroxazole is described employing an intramolecular Diels-Alder cyclization and an iodine-mediated oxidative aromatization step.
- Yadav,Bhasker, E. Vijaya,Srihari
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experimental part
p. 1997 - 2004
(2010/04/29)
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- Development of N,N-bis(perfluoroalkanesulfonyl)squaramides as new strong Br?nsted acids and their application to organic reactions
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New strong Br?nsted acids derived from a squaric acid scaffold bearing different perfluoroalkanesulfonyl groups have been developed and applied to several organic reactions. These squaramides are bench-stable and exhibit much higher reactivities in several organic reactions than squaric acid itself. N,N-Bis(trifluoromethanesulfonyl)squaramide 2a was applied to the Mukaiyama aldol reaction and Mukaiyama Michael reaction. Mechanistic studies revealed that the Br?nsted acid might be the predominant catalyst through direct protonation of carbonyl compound by the acid itself rather than the silylated Br?nsted acid. The utility of this acid 2a was further extended to Hosomi-Sakurai allylation of aldehydes and a carbonyl-ene reaction. Furthermore, other squaramides 2b and c bearing longer perfluoroalkyl chains have been developed, which are also bench-stable and displayed similar reactivities with squaramide 2a in several organic reactions.
- Cheon, Cheol Hong,Yamamoto, Hisashi
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supporting information; experimental part
p. 4257 - 4264
(2010/07/06)
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- One-pot synthesis of menthol catalyzed by a highly diastereoselective Au/MgF2 catalyst
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No toxic compounds such as KCN and no thermal activation is required for the preparation of Au/MgF2 complexes by a simple and facile incipient wetness impregnation method in which hydrogen tetrachloroaurate (HAuCl 4) is the gold precursor. One of the complexes prepared exhibits unique catalytic properties and serves as a heterogeneous catalyst for the highly diastereoselective one-pot synthesis of (±)-menthol from citronellal (see picture).
- Negoi, Alina,Wuttke, Stefan,Kemnitz, Erhard,MacOvei, Dan,Parvulescu, Vasile I.,Teodorescu,Coman, Simona M.
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supporting information; scheme or table
p. 8134 - 8138
(2011/02/24)
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- One-step microwave-assisted asymmetric cyclisation/hydrogenation of citronellal to menthols using supported nanoparticles on mesoporous materials
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The selective conversion of citronellal to menthols, with good diastereoselectivities to (-)-menthol for the case of (+)-citronellal as starting material, can effectively be carried out in a one-step reaction under microwave irradiation catalysed by supported nanoparticles on mesoporous materials. 2% Pt/Ga-MCM-41 was found to be the optimum catalyst for the reaction, with a quantitative conversion of starting material and selectivities above 85% to menthols obtained in short reaction times (typically 15 min). These results constitute the first report of a simple microwave-assisted one-step cyclisation/hydrogenation process for the production of menthols.
- Balu, Alina Mariana,Campelo, Juan Manuel,Luque, Rafael,Romero, Antonio Angel
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experimental part
p. 2845 - 2849
(2010/08/21)
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- RECOVERY OF BIS(DIARYLPHENOL) LIGANDS DURING THE PRODUCTION OF ISOPULEGOL
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The present invention relates to a method of working up an aluminium-containing reaction product from the production of isopulegol by cyclization of citronellal in the presence of complex compounds, comprising at least one ligand of the formula (I), where Ar1, Ar2, Ar3, Ar4 are chosen from C6-C15-aryl or C2-C15-hetero; R1, R2, R3, R4 are chosen from H, C1-C6-alkyl, C1-C6-perfluoroalkyl, C1-C6-alkoxy, C7-C12-aralkyl, halogen, SiR5bR6bR7b, C6-C10-aryl, NR8bR9b, SR10b, NO2; and where R1 or R2 and/or R3 or R4, together with A, can form an aromatic or nonaromatic cycle; etc.; in which a) the aluminum-containing reaction product is subjected to distillative separation, b) the isopulegol-depleted bottom product is brought into close contact with an aqueous base and c) the ligand of the formula (I) is separated off from the organic phase, preferably by crystallization. Moreover, the invention relates to a method of producing isopulegol, and to a method of producing menthol.
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Page/Page column 17-18
(2010/02/17)
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- Sc(OTf)3-catalyzed one-pot ene-Prins cyclization: a novel synthesis of octahydro-2H-chromen-4-ols
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(R)-Citronellal undergoes initial ene reaction followed by Prins cyclization with aldehydes in the presence of 5 mol % of scandium triflate at ambient temperature to furnish octahydro-2H-chromen-4-ols in good yields and with high cis-selectivity. The use of scandium triflate makes this procedure simple, more convenient, and practical.
- Yadav,Reddy, B.V. Subba,Ganesh,Narayana Kumar
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experimental part
p. 2963 - 2966
(2010/06/21)
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- ALUMINIUM COMPLEXES AND USE THEREOF AS A CATALYST IN INTRAMOLECULAR RING CLOSURE REACTIONS
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To provide a process for increasing the proportion of an optical isomer of not only a compound having a closed ring but also a compound not having a closed ring when an optical isomer mixture of a compound having both a formyl group and a double bond capable of causing a carbonyl-ene ring closing reaction in the same molecule is subjected to a ring closing reaction. A process for increasing the proportion of an optical isomer characterized by subjecting an optical isomer mixture of a compound having both a formyl group and a double bond capable of causing a carbonyl-ene ring closing reaction in the same molecule to a ring closing reaction in the presence of a predetermined aluminum complex represented by the general formula: [All(L1)l(L2)m(Lh)n]k.
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Page/Page column 53-55
(2010/08/05)
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- ALUMINIUM COMPLEXES AND USE THEREOF AS A CATALYST IN INTRAMOLECULAR RING CLOSURE REACTIONS
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To provide a process for increasing the proportion of an optical isomer of not only a compound having a closed ring but also a compound not having a closed ring when an optical isomer mixture of a compound having both a formyl group and a double bond capable of causing a carbonyl-ene ring closing reaction in the same molecule is subjected to a ring closing reaction. A process for increasing the proportion of an optical isomer characterized by subjecting an optical isomer mixture of a compound having both a formyl group and a double bond capable of causing a carbonyl-ene ring closing reaction in the same molecule to a ring closing reaction in the presence of a predetermined aluminum complex represented by the general formula: [Al2(L1)n(L2)3-n]m.
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Page/Page column 43-44
(2010/08/05)
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