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Sustainable p-cymene and hydrogen from limonene
A fine chemical intermediate in a wide range of chemical processes, p-cymene, has been obtained from Limonene, solids based on a natural clay (sepiolite) modified with sodium, nickel, iron or manganese oxides and programmable focalised microwaves. The process has the added bonus of one mol of hydrogen being produced per mol of limonene converted to p-cymene.
Martin-Luengo,Yates,Rojo, E. Saez,Huerta Arribas,Aguilar,Ruiz Hitzky
p. 141 - 146
(2010)
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Aromatization of Hydrocarbons y Oxidative Dehydrogenation Catalyzed by the Mixed Addenda Heteropoly Acid H5PMo10V2O40
The mixed addenda heteropoly acid H5PMo10V2O40 dissolved in 1,2-dichloroethane with tetraglyme, forming the (tetraglyme)3-H5PMo10V2O40 complex, catalyzes the aromatization of cyclic dienes at moderate temperatures in the presence of molecular oxygen.Dehydrogenations of exocyclic dienes such as limonene show that dehydrogenation is preceded by isomerization to their endocyclic isomers.Aromatization takes place by succesive one-electron transfers and proton abstractions from the organic substrate to the heteropoly acid, the latter being reoxidized by dioxygen coupled with the formation of water.
Neumann, Ronny,Lissel, Manfred
p. 4607 - 4610
(1989)
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Diverse Mechanistic Pathways in Single-Site Heterogeneous Catalysis: Alcohol Conversions Mediated by a High-Valent Carbon-Supported Molybdenum-Dioxo Catalyst
With the increase in the importance of renewable resources, chemical research is shifting focus toward substituting petrochemicals with biomass-derived analogues and platform-molecule transformations such as alcohol processing. To these ends, in-depth mechanistic understanding is key to the rational design of catalytic systems with enhanced activity and selectivity. Here we discuss in detail the structure and reactivity of a single-site active carbon-supported molybdenum-dioxo catalyst (AC/MoO2) and the mechanism(s) by which it mediates alcohol dehydration. A range of tertiary, secondary, and primary alcohols as well as selected bio-based terpineols are investigated as substrates under mild reaction conditions. A combined experimental substituent effect/kinetic/kinetic isotope effect/EXAFS/DFT computational analysis indicates that (1) water assistance is a key element in the transition state; (2) the experimental kinetic isotopic effect and activation enthalpy are 2.5 and 24.4 kcal/mol, respectively, in good agreement with the DFT results; and (3) several computationally identified intermediates including Mo-oxo-hydroxy-alkoxide and cage-structured long-range water-coordinated Mo-dioxo species are supported by EXAFS. This structurally and mechanistically well-characterized single-site system not only effects efficient transformations but also provides insight into rational catalyst design for future biomass processes.
Bedzyk, Michael J.,Das, Anusheela,Kratish, Yosi,Li, Jiaqi,Ma, Qing,Marks, Tobin J.
p. 1247 - 1257
(2022/02/07)

Preparation method of isopentylene
The method comprises the following steps: taking dipentene as a raw material, and using acetic acid in a high-pressure carbon dioxide environment. Isoterpinene is prepared by reacting acetate and an axial chiral nitrogen-containing compound as a catalyst. The axial chiral nitrogen-containing compound is one or more of an axial chiral nitrogen-containing binaphthyl or biphenyl compound. The selectivity and yield of terpinene are high.
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Paragraph 0031-0050

(2021/11/10)

Preparation of α-terpineol and perillyl alcohol using zeolites beta
The preparation of α-terpineol by direct hydration of limonene catalyzed by zeolites beta was studied. The same catalyst was used to prepare perillyl alcohol by isomerization of β-pinene oxide in the presence of water. The aim was to optimize the reaction conditions to achieve high conversions of starting material and high selectivity to the desired products. In the case of limonene, it was found that the highest selectivity to α-terpineol was 88% with conversion of 36% under the conditions: 50?wt% of catalyst beta 25, 10% aqueous acetic acid (10?mL) (volume ratio limonene:H2O = 1:4.5), temperature 50?°C, after 24?h. In the case of β-pinene oxide, it was found that the highest selectivity to perillyl alcohol, which was 36% at total conversion, was obtained in the reaction under the following conditions: dimethyl?sulfoxide as solvent (volume ratio β-pinene oxide:DMSO = 1:5), catalyst beta 25 without calcination (15?wt%), demineralized water (molar ratio β-pinene oxide:H2O = 1:8), temperature 70?°C, 3?h. The present study shows that the studied reactions are suitable for the selective preparation of chosen compounds.
?erveny, Libor,Vysko?ilová, Eli?ka,Zítová, Kate?ina
p. 4297 - 4310
(2021/07/26)

Thioderivatives of Resorcin[4]arene and Pyrogallol[4]arene: Are Thiols Tolerated in the Self-Assembly Process?
Three novel thiol bearing resorcin[4]arene and pyrogallol[4]arene derivatives were synthesized. Their properties were studied with regards to self-assembly, disulfide chemistry, and Br?nsted acid catalysis. This work demonstrates that (1) one aromatic thiol on the resorcin[4]arene framework is tolerated in the self-assembly process to a hexameric hydrogen bond-based capsule, (2) thio-derivatized resorcin[4]arene analogs can be covalently linked through disulfides, and (3) the increased acidity of aromatic thio-substituent is not sufficient to replace HCl as cocatalyst for capsule catalyzed terpene cyclizations.
Nemat, Suren J.,Tiefenbacher, Konrad
supporting information
p. 6861 - 6865
(2021/09/14)

STRONGLY LEWIS ACIDIC METAL-ORGANIC FRAMEWORKS FOR CONTINUOUS FLOW CATALYSIS
Lewis acidic metal-organic framework (MOF) materials comprising triflate-coordinated metal nodes are described. The materials can be used as heterogenous catalysts in a wide range of organic group transformations, including Diels-Alder reactions, epoxide-ring opening reactions, Friedel-Crafts acylation reactions and alkene hydroalkoxylation reactions. The MOFs can also be prepared with metallated organic bridging ligands to provide heterogenous catalysts for tandem reactions and/or prepared as composites with support particles for use in columns of continuous flow reactor systems. Methods of preparing and using the MOF materials and their composites are also described.
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Paragraph 0166; 0168

(2021/02/26)

Monoterpenes etherification reactions with alkyl alcohols over cesium partially exchanged Keggin heteropoly salts: effects of catalyst composition
In this work, cesium partially exchanged Keggin heteropolyacid (HPA) salts were prepared, characterized, and evaluated as solid catalysts in monoterpenes etherification reactions with alkyl alcohols. A comparison of the activity of soluble HPAs and their insoluble cesium salts showed that among three different Keggin anions the phosphotungstate was the most efficient catalyst. Assessments on the effects of the level of the protons exchange by cesium cations demonstrated that Cs2.5H0.5PW12O40 solid salt was the most active and selective phosphotungstate catalyst, converting β-pinene to α-terpinyl methyl ether. The influences of the main reaction parameters such as reaction temperature, time, catalyst load, substrate nature (i.e., alcohols and monoterpenes) were investigated. We have demonstrated that the simultaneous presence of the cesium ions and protons in the catalyst plays an essential role, being the 2.5–0.5 the optimum molar ratio. The Cs2.5H0.5PW12O40 salt was efficiently recovered and reused without loss of catalytic activity. Graphic abstract: [Figure not available: see fulltext.]
da Silva, Márcio José,Lopes, Neide Paloma Goncalves,Ferreira, Sukarno Olavo,da Silva, Rene Chagas,Natalino, Ricardo,Chaves, Diego Morais,Texeira, Milena Galdino
p. 153 - 168
(2020/07/21)

Multistep Engineering of Synergistic Catalysts in a Metal-Organic Framework for Tandem C-O Bond Cleavage
Cleavage of strong C-O bonds without breaking C-C/C-H bonds is a key step for catalytic conversion of renewable biomass to hydrocarbon feedstocks. Herein we report multistep sequential engineering of orthogonal Lewis acid and palladium nanoparticle (NP) catalysts in a metal-organic framework (MOF) built from (Al-OH)n secondary building units and a mixture of 2,2′-bipyridine-5,5′-dicarboxylate (dcbpy) and 1,4-benzenediacrylate (pdac) ligands (1) for tandem C-O bond cleavage. Ozonolysis of 1 selectively removed pdac ligands to generate Al2(OH)(OH2) sites, which were subsequently triflated with trimethylsilyl triflate to afford strongly Lewis acidic sites for dehydroalkoxylation. Coordination of Pd(MeCN)2Cl2 to dcbpy ligands followed by in situ reduction produced orthogonal Pd NP sites in 1-OTf-PdNP as the hydrogenation catalyst. The selective and precise transformation of 1 into 1-OTf-PdNP was characterized step by step using powder X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, inductively coupled plasma mass spectrometry, infrared spectroscopy, and X-ray absorption spectroscopy. The hierarchical incorporation of orthogonal Lewis acid and Pd NP active sites endowed 1-OTf-PdNP with outstanding catalytic performance in apparent hydrogenolysis of etheric, alcoholic, and esteric C-O bonds to generate saturated alkanes via a tandem dehydroalkoxylation-hydrogenation process under relatively mild conditions. The reactivity of C-O bonds followed the trend of tertiary carbon > secondary carbon > primary carbon. Control experiments demonstrated the heterogeneous nature and recyclability of 1-OTf-PdNP and its superior catalytic activity over the homogeneous counterparts. Sequential engineering of multiple catalytic sites in MOFs thus presents a unique opportunity to address outstanding challenges in sustainable catalysis.
Brzezinski, Carter,Chen, Justin S.,Feng, Xuanyu,Lin, Wenbin,Song, Yang,Xu, Ziwan
supporting information
p. 4872 - 4882
(2020/04/01)

Requirements for Terpene Cyclizations inside the Supramolecular Resorcinarene Capsule: Bound Water and Its Protonation Determine the Catalytic Activity
The elucidation of the requirements for efficient catalysis within supramolecular host systems is an important prerequisite for developing novel supramolecular catalysts. The resorcinarene hexamer has recently been shown to be the first supramolecular catalyst to promote the tail-to-head terpene cyclization in a biomimetic fashion. We herein present the synthesis of a number of resorcinarene-based macrocycles composed of different ratios of resorcinol and pyrogallol units capable of self-assembly and compare the corresponding assemblies regarding their catalytic activity in the cyclization of monoterpenes. The assemblies were investigated in detail with respect to a number of properties including the encapsulation of substrate and ion pairs, the structural incorporation of water, and the response to externally added acid (HCl). The results obtained strongly indicate that water incorporated into the hydrogen-bond network of the self-assembled structure plays an integral role for catalysis, effectively acting as a proton shuttle to activate the encapsulated substrate. These findings are also supported by molecular dynamics simulations, providing further insight into the protonation pathway and the relative energies of the intermediates involved.
Merget, Severin,Catti, Lorenzo,Piccini, Giovannimaria,Tiefenbacher, Konrad
supporting information
p. 4400 - 4410
(2020/03/04)

Enantioselective Tail-to-Head Cyclizations Catalyzed by Dual-Hydrogen-Bond Donors
Chiral urea derivatives are shown to catalyze enantioselective tail-to-head cyclization reactions of neryl chloride analogues. Experimental data are consistent with a mechanism in which ?-participation by the nucleophilic olefin facilitates chloride ionization and thereby circumvents simple elimination pathways. Kinetic and computational studies support a cooperative mode of catalysis wherein two molecules of the urea catalyst engage the substrate and induce enantioselectivity through selective transition state stabilization.
Kutateladze, Dennis A.,Strassfeld, Daniel A.,Jacobsen, Eric N.
p. 6951 - 6956
(2020/05/19)

Controllable Isomerization of Alkenes by Dual Visible-Light-Cobalt Catalysis
We report herein that thermodynamic and kinetic isomerization of alkenes can be accomplished by the combination of visible light with Co catalysis. Utilizing Xantphos as the ligand, the most stable isomers are obtained, while isomerizing terminal alkenes over one position can be selectively controlled by using DPEphos as the ligand. The presence of the donor–acceptor dye 4CzIPN accelerates the reaction further. Transformation of exocyclic alkenes into the corresponding endocyclic products could be efficiently realized by using 4CzIPN and Co(acac)2 in the absence of any additional ligands. Spectroscopic and spectroelectrochemical investigations indicate CoI being involved in the generation of a Co hydride, which subsequently adds to alkenes initiating the isomerization.
Meng, Qing-Yuan,Schirmer, Tobias E.,Katou, Kousuke,K?nig, Burkhard
supporting information
p. 5723 - 5728
(2019/04/03)

Discovering Monoterpene Catalysis Inside Nanocapsules with Multiscale Modeling and Experiments
Large-scale production of natural products, such as terpenes, presents a significant scientific and technological challenge. One promising approach to tackle this problem is chemical synthesis inside nanocapsules, although enzyme-like control of such chemistry has not yet been achieved. In order to better understand the complex chemistry inside nanocapsules, we design a multiscale nanoreactor simulation approach. The nanoreactor simulation protocol consists of hybrid quantum mechanics-molecular mechanics-based high temperature Langevin molecular dynamics simulations. Using this approach we model the tail-to-head formation of monoterpenes inside a resorcin[4]arene-based capsule (capsule I). We provide a rationale for the experimentally observed kinetics of monoterpene product formation and product distribution using capsule I, and we explain why additional stable monoterpenes, like camphene, are not observed. On the basis of the in-capsule I simulations, and mechanistic insights, we propose that feeding the capsule with pinene can yield camphene, and this proposal is verified experimentally. This suggests that the capsule may direct the dynamic reaction cascades by virtue of π-cation interactions.
Pahima, Efrat,Zhang, Qi,Tiefenbacher, Konrad,Major, Dan T.
p. 6234 - 6246
(2019/04/25)

Highly efficient rhodium-phosphite catalyzed hydroformylation of camphene and other terpenes
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Pagar, Nitin S.,Deshpande, Raj M.
p. 213 - 219
(2018/12/11)

Exploring the Keggin-Type Heteropolyacid-Catalyzed Reaction Pathways of the Β-Pinene with Alkyl Alcohols
Abstract: In this work, we investigated the activity of Keggin heteropolyacid catalysts (i.e., H3PW12O40, H3PMo12O40 and H4SiW12O40) in β-pinene reactions with alkyl alcohols (i.e. methyl, ethyl, propyl, sec-propyl, butyl and sec-butyl alcohols), and exploring the different aspects that drive the selectivity of this process. We have found that carbon skeletal rearrangements and isomerization providing intermediate carbocations that controlling the reaction selectivity. β-pinene was preferentially converted to α-terpinyl ion which undergoes a nucleophilic attack of alcohol providing alkyl alcohol. Bornyl ion was converted to bornyl and fenchyl ethers. The other secondary products were β-pinene isomers obtained from bornyl and α-terpinyl carbocations. Phosphotungstic acid (i.e., H3PW12O40) was the most active catalyst and selective toward the main product (α-terpinyl alkyl ether); the highest conversion (ca. 96%) and ether selectivity (ca. 61%) was achieved in the reactions with β-pinene. Although having also been alkoxylate, α-pinene was less reactive (ca. 40%), while camphene and limonene remained unreactive under reaction conditions studied. An increase of temperature resulted in an improvement on conversion of β-pinene and selectivity toward α-terpinyl methyl ether. Similarly, the H3PW12O40 concentration played a crucial role on reaction selectivity. This work presents positive features such as a short reaction time, high atom economy, mild reaction conditions (i.e., low temperature and room pressure). Even though soluble the catalyst was easily recovered by liquid -liquid extraction and efficiently reused. Graphical Abstract: [Figure not available: see fulltext.].
Polo, Henrique Priori,Lopes, Neide Paloma Goncalves,da Silva, Márcio José
p. 2844 - 2853
(2019/05/28)

SnCl2-catalyzed synthesis of carbamates from renewable origin alcohols
Effects of structure and reactivity of renewable origin alcohols in the conversion and selectivity of the SnCl2-catalyzed reactions in the presence and absence of urea were assessed. Convenient simple and suitable method for the synthesis of carbamates from renewable origin alcohols and urea in one-step are provided. We have assessed the activity of SnCl2 catalyst, a commercially affordable Lewis acid, in reactions of urea alcoholysis with different natural origin alcohols (geranyl, neryl, bornyl, cinnamyl, α-terpinyl and benzyl alcohols), aiming to synthesize carbamates, which are biologically active compounds, building blocks in organic synthesis and raw material to synthesize polyurethanes. The low cost of urea, the water tolerant catalyst and phosgene free reaction are positive aspects of this carbamates synthesis process. The different reaction pathways were assessed. A mechanism was proposed based on FT-IR experiments and experimental data.
da Silva, Márcio José,Chaves, Diego Morais
p. 1169 - 1180
(2019/01/28)

Transition metal triflate catalyzed conversion of alcohols, ethers and esters to olefins
Herein, we report an efficient transition metal triflate catalyzed approach to convert biomass-based compounds, such as monoterpene alcohols, sugar alcohols, octyl acetate and tea tree oil, to their corresponding olefins in high yields. The reaction proceeds through C-O bond cleavage under solvent-free conditions, where the catalytic activity is determined by the oxophilicity and the Lewis acidity of the metal catalyst. In addition, we demonstrate how the oxygen containing functionality affects the formation of the olefins. Furthermore, the robustness of the used metal triflate catalysts, Fe(OTf)3 and Hf(OTf)4, is highlighted by their ability to convert an over 2400-fold excess of 2-octanol to octenes in high isolated yields.
Keskiv?li,Parviainen,Lagerblom,Repo
p. 15111 - 15118
(2018/05/04)

Terpene Cyclizations inside a Supramolecular Catalyst: Leaving-Group-Controlled Product Selectivity and Mechanistic Studies
The tail-to-head terpene cyclization is arguably one of the most complex reactions found in nature. The hydrogen-bond-based resorcinarene capsule represents the first man-made enzyme-like catalyst that is capable of catalyzing this reaction. Based on noncovalent interactions between the capsule and the substrate, the product selectivity can be tuned by using different leaving groups. A detailed mechanistic investigation was performed to elucidate the reaction mechanism. For the cyclization of geranyl acetate, it was found that the cleavage of the leaving group is the rate-determining step. Furthermore, the studies revealed that trace amounts of acid are required as cocatalyst. A series of control experiments demonstrate that a synergistic interplay between the supramolecular capsule and the acid traces is required for catalytic activity.
Zhang, Qi,Catti, Lorenzo,Pleiss, Jürgen,Tiefenbacher, Konrad
p. 11482 - 11492
(2017/08/30)

High density fuels from oxygenated terpenoids
A method for the efficient synthesis of useful deoxygenated terpenoids from an abundant renewable source, using catalytic conversion of oxygenated terpenoids. Oxygenated terpenoids such as 1,4-cineole and 1,8-cineole are, for example, major components of turpentine and essential oils. These oxygenated terpenoids can also be produced from sugars via a biosynthetic approach. Catalytic deoxygenation of these substrates can be used to efficiently generate commercially important chemicals and high density fuels for turbine or diesel propulsion.
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(2017/07/06)

Mechanisms into dehydroaromatization of bio-derived limonene to: P -cymene over Pd/HZSM-5 in the presence and absence of H2
The mechanisms of dehydroaromatization of limonene to p-cymene are intrinsically investigated over Pd/HZSM-5 under different N2/H2 atmospheres using the mathematical tool of Matlab. It is found that the dehydroaromatization reaction network starts with the isomerization step, and is followed by the sequential dehydrogenation in the presence of N2 or H2 at the selected system. The addition of hydrogen in the atmosphere would not change this reaction pathway, but leads to lower selectivity of p-cymene due to the accelerated hydrogenation rates on the double bonds. Besides, the additional hydrogen speeds up the overall reaction by facilitating the isomerization step on limonene while impeding its reverse reaction, as isomerization of limonene is proved to be the determining step of the whole dehydroaromatization reaction. Furthermore, the presence of hydrogen dramatically decreases the apparent and true activity energy of the target dehydroaromatization reaction and reduces the impact of temperatures to such processes compared to that with a N2 gas carrier.
Cui, Huimei,Zhang, Jingjing,Luo, Zhicheng,Zhao, Chen
p. 66695 - 66704
(2016/08/02)

Acidic functionalized ionic liquids as catalyst for the isomerization of α-pinene to camphene
An acidic functionalized ionic liquids (ILs) [HSO3-(CH2)3-NEt3]Cl-ZnCl2 was synthesized and used to catalyze the isomerization of α-pinene in a homogeneous system. The optimum conditions for isomerization were obtained as follows: n(α-pinene):n(ILs) = 9:1, reaction temperature 140 °C, and reaction time 4 h, α-pinene 0.04 mol. Under the optimal conditions, the conversion of α-pinene was 97.6 % and the selectivity for camphene could reach 64.8 %. In addition, the catalyst could be easily separated by centrifugation after the isomerization completely finished. When the ILs were repeatedly used for four times, the conversion of α-pinene and the selectivity for camphene were still excellent, indicating the superb recycle ability of the acidic functionalized ILs catalyst.
Liu, Yue,Li, Lu,Xie, Cong Xia
p. 559 - 569
(2016/04/26)

Support Functionalization with a Phosphine-Containing Hyperbranched Polymer: A Strategy to Enhance Phosphine Grafting and Metal Loading in a Hydroformylation Catalyst
We present the design of a hydroformylation catalyst through the immobilization of air-stable Rh nanoparticles (NPs) on a magnetic support functionalized with a hyperbranched polymer that bears terminal phosphine groups. The catalyst modification with the hyperbranched polymer improved the metal–support interaction, the metal loading, and the catalytic activity. The catalyst was active for the hydroformylation of natural products, such as estragole, and could be used in successive reactions with negligible metal leaching. The phosphine grafting played a key role in the recyclability of Rh NPs under hydroformylation conditions. The catalytic activity was maintained in successive reactions, even if the catalyst was exposed to air during each recovery procedure. The modification of the support with hyperbranched polyester allowed us either to increase the number of Rh active species or to obtain more active Rh species on the catalyst surface.
Garcia, Marco A. S.,Heyder, Rodrigo S.,Oliveira, Kelley C. B.,Costa, Jean C. S.,Corio, Paola,Gusevskaya, Elena V.,dos Santos, Eduardo N.,Bazito, Reinaldo C.,Rossi, Liane M.
p. 1951 - 1960
(2016/07/06)

Unravelling transition metal-catalyzed terpenic alcohol esterification: A straightforward process for the synthesis of fragrances
Iron nitrate is a simple and commercially available Lewis acid and is demonstrated to be able to catalyze β-citronellol esterification with acetic acid, achieving high conversion and ester selectivity (ca. 80 and 70%, respectively), within shorter reaction times than those reported in the literature. To the best of our knowledge, this is the first report of a terpenic alcohol esterification reaction catalyzed by Fe(NO3)3. This process is an attractive alternative to the slow and expensive enzymatic processes commonly used in terpenic alcohol esterification. Moreover, it avoids the undesirable steps of neutralizing the products, which are always required in mineral acid-catalyzed reactions. We have performed a study of the activity of different metal Lewis acid catalysts, and found that their efficiency is directly linked to the ability of the metal cation to generate H+ ions from acetic acid ionization. The measurement of pH as well as the conversions achieved in the reactions allowed us to obtain the following trend: Fe(NO3)3 > Al(NO3)3 > Cu(NO3)2 > Ni(NO3)2 > Zn(NO3)2 > Mn(NO3)2 > Co(NO3)2 > LiNO3. The first three are recognized as stronger Lewis acids and they generate more acidic solutions. When we carried out reactions with different iron salts, it was possible to conclude that the type of anion affects the solubility of the catalyst, as well as the conversion and selectivity of the process. Fe2(SO4)3 and FeSO4 were insoluble and less active. Conversely, though they were equally soluble, Fe(NO3)3 was more selective for the formation of β-citronellyl acetate than FeCl3. We assessed the effects of the main reaction variables such as reactant stoichiometry, temperature, and catalyst concentration. In addition to citronellol, we investigated the efficiency of the iron(iii) catalyst in the solvent free esterification of several terpenic alcohols (geraniol, nerol, linalool, α-terpineol) as well as other carboxylic acids.
Da Silva,Ayala
p. 3197 - 3207
(2016/05/24)

A new approach for bio-jet fuel generation from palm oil and limonene in the absence of hydrogen
The traditional methodology includes a carbon-chain shortening strategy to produce bio-jet fuel from lipids via a two-stage process with hydrogen. Here, we propose a new solution using a carbon-chain filling strategy to convert C10 terpene and lipids to jet fuel ranged hydrocarbons with aromatic hydrocarbon ingredients in the absence of hydrogen.
Zhang, Jingjing,Zhao, Chen
p. 17249 - 17252
(2015/12/08)

Selective methoxylation of α-pinene to α-terpinyl methyl ether over Al3+ ion-exchanged clays
In this study, we report the use of clay-based catalysts in the methoxylation of α-pinene, for the selective synthesis of α-terpinyl methyl ether, TME. The main reaction products and intermediates were identified by GC-MS. The reaction conditions (stirring rate and catalyst load) that afford a kinetic regime were established. SAz-1 (Cheto, Arizona, USA) source clay and a montmorillonite (SD) from Porto Santo, Madeira Archipelago, Portugal, were modified by ion-exchange with Al3+ to produce catalysts with markedly different acidities and textural properties. The catalysts based on the high layer-charge SAz-1 montmorillonite proved to be the most active. Ion-exchange with Al3+, followed by thermal activation at 150°C, afforded the highest number of Br?nsted acid sites - a significant proportion of which were located in the clay gallery - and this coincided with the maximum catalytic activity. The influence of various reaction conditions, to maximize α-pinene conversion and selectivity, was studied over AlSAz-1. When the reaction was performed for 1 h at 60°C, the conversion reached 65% with 65% selectivity towards the mono-ether, TME. Similar conversions and selectivities required up to 50 h over zeolites and other solid acid catalysts. The kinetic dependencies of this reaction on temperature and reagent concentration, over the selected clays were also investigated. It was established that, in the temperature and reagent concentration regime studied, the reaction was first order with respect to α-pinene. The apparent activation energies over the two catalysts, calculated from Arrhenius plots, were almost identical at 72 kJ mol-1.
Catrinescu,Fernandes,Castilho,Breen
p. 171 - 179
(2015/05/05)

Terpene cyclization catalysed inside a self-assembled cavity
In nature, complex terpene natural products are formed by the so-called tail-to-head terpene (THT) cyclization. The cationic reaction cascade is promoted efficiently in complex enzyme pockets, in which cationic intermediates and transition states are stabilized. In solution, the reaction is hard to control and man-made catalysts able to perform selective THT cyclizations are lacking. We herein report the first example of a successful THT cyclization inside a supramolecular structure. The basic mode of operation in cyclase enzymes was mimicked successfully and a catalytic non-stop THT was achieved with geranyl acetate as the substrate. The results presented have implications for the postulated reaction mechanism in cyclase enzymes. Evidence indicates that the direct isomerization of a geranyl cation to the cisoid isomer, which so far was considered unlikely, is feasible.
Zhang, Q.,Tiefenbacher, K.
p. 197 - 202
(2015/04/21)

Selective carvone hydrogenation to dihydrocarvone over titania supported gold catalyst
Selective hydrogenation of natural carvone to industrially valuable dihydrocarvone was carried out at 100°C under hydrogen pressure over a 1.9wt.% Au/TiO2 catalyst. The gold catalyst has demonstrated high activity as well as stereo- and chemoselectivity in conjugated C=C double bond hydrogenation with predominant formation of trans-dihydrocarvone. The catalytic activity and trans-to cis-isomers ratio were shown to strongly depend on the solvent. In a range of C1 - C3 alcohol solvents both catalytic activity and trans-to cis-dihydrocarvone ratio increased following the order: 2-propanol a nearly complete carvone conversion (90%) after 13h in the case of methanol, with the trans-to cis-dihydrocarvone ratio being about 1.8. Based on the transition state theory a quantitative description of trans-to cis-dihydrocarvone ratio variations in different solvents was made.
Demidova,Suslov,Simakova,Simakova,Volcho,Salakhutdinov,Murzin
p. 189 - 194
(2015/03/14)

Radical titanocene promoted coupling of epoxides and vinyl sulfones
A radical coupling reaction of diverse vinyl sulfones and epoxides was mediated by Cp2TiCl (Cp = cyclopentadienyl) to provide a straightforward synthetic pathway to hydroxy sulfones. The reaction was successfully achieved by using either an excess or a catalytic amount of the TiIII reagent. The scope of the reaction was studied for several different functionalized and substituted epoxides and vinyl sulfones.
Fernndez-Mateos, Alfonso,Encinas-Madrazo, Soledad,Herrero-Teijn, Pablo,Gonzlez, Rosa Rubio
p. 548 - 555
(2015/01/30)

Isotope sensitive branching and kinetic isotope effects to analyse multiproduct terpenoid synthases from Zea mays
Multiproduct terpene synthases TPS4-B73 and TPS5-Delprim from Zea mays exhibit isotopically sensitive branching in the formation of mono- and sesquiterpene volatiles. The impact of the kinetic isotope effects and the stabilization of the reactive intermediates by hyperconjugation along with the shift of products from alkenes to alcohols are discussed.
Gatto, Nathalie,Vattekkatte, Abith,K?llner, Tobias,Degenhardt, J?rg,Gershenzon, Jonathan,Boland, Wilhelm
supporting information
p. 3797 - 3800
(2015/03/30)

The selective conversion of D-limonene to p,α-dimethylstyrene
Reaction conditions to facilitate the conversion of D-limonene selectively to p,α-dimethylstyrene (DMS) are described, in order to subsequently produce polymeric materials from biomass sourced from food waste. Limonene was dehydrogenated with several palladium catalysts and different solvents and bases, with copper chloride as oxidant at temperatures of 70-120 °C. Reaction conditions were identified using Pd(OAc)2 for the selective formation of only DMS from limonene in 2-5 hours, enabling the facile separation of DMS from unreacted starting material by vacuum distillation.
Sanchez-Vazquez,Sheppard,Evans,Hailes
p. 61652 - 61655
(2015/02/19)

Hydrothermal synthesis of single-crystalline mesoporous beta zeolite assisted by N-methyl-2-pyrrolidone
Highly crystalline beta zeolite with large intracrystalline mesopores has been facilely synthesized via the introduction of low-cost N-methyl-2- pyrrolidone (NMP) into common TEAOH-based zeolite synthesis mixtures, which exhibited remarkably higher catalytic activity contrast than conventional porous catalysts (ZSM-5, beta and Al-MCM-41) in acid-catalyzed reactions involving large molecules.
Liu, Lijia,Wang, Hongbin,Wang, Runwei,Zeng, Shangjing,Ni, Ling,Zhang, Daliang,Zhu, Liangkui,Zou, Houbing,Qiu, Shilun,Zhang, Zongtao
p. 39297 - 39300
(2014/11/08)

Superacidity in sulfated metal-organic framework-808
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.
supporting information
p. 12844 - 12847
(2015/12/26)

Synthesis of mesoporous Beta and Sn-Beta zeolites and their catalytic performances
Mesoporous Beta zeolite has been successfully prepared through hydrothermal synthesis in the presence of cationic ammonium-modified chitosan as the meso-template. Through a subsequent solid-gas reaction between highly dealuminated mesoporous Beta zeolite and SnCl4 steam at an elevated temperature, mesoporous Sn-Beta has been facilely obtained. It was revealed that the addition of cationic chitosan induced the nanocrystal aggregation to particle sizes of ～300 nm, giving rise to the intercrystalline/interparticle mesoporosity. In the Sn-implanting procedure, Sn species were demonstrated to be doped into the framework of the resulting mesoporous Beta zeolite in a tetrahedral environment without structural collapse. Due to the micro/mesoporous structures, both mesoporous Beta and Sn-Beta exhibited superior performances in α-pinene isomerization, Baeyer-Villiger oxidation of 2-adamantanone by hydrogen peroxide and the isomerization of glucose in water, respectively. the Partner Organisations 2014.
Jin, Junjiang,Ye, Xinxin,Li, Yongsheng,Wang, Yanqin,Li, Liang,Gu, Jinlou,Zhao, Wenru,Shi, Jianlin
p. 8196 - 8204
(2014/06/09)

Effect of high-temperature calcination on the generation of Bronsted acid sites on WO3/Al2O3
The acid properties of a series of alumina-supported tungsten oxide (WO3/Al2O3) catalysts with loadings of 5-50 wt% WO3 calcined at various temperatures were investigated by acid-catalyzed reactions (benzylation of anisole and isomerization of α-pinene) and FTIR spectroscopy. The relationships between acid properties, structures, and catalytic performances were evaluated. Both the catalytic activity and amount of Bronsted acid sites depend on the calcination temperature and WO3 loading. High-temperature calcination (1123 K) generated Bronsted acid properties, and 20 wt% WO 3/Al2O3 calcined at 1123 K exhibited the highest activity among the catalysts tested. The activities for the benzylation of anisole and α-pinene isomerization over WO3/Al 2O3 calcined at 1123 K were proportional to the Bronsted acidity, which indicates that these reactions occurred on the Bronsted acid sites. Tungsten oxide, which has distorted octahedral symmetry, was loaded as 2D monolayer domains below 20 wt%, and these domains covered most of the alumina surface at 20 wt%. If the WO3 loading was sufficient to form 2D tungsten oxide monolayer sheets (>20 wt%), some of the Bronsted acid sites on WO3/Al2O3 were obscured by monoclinic WO3 that has no Bronsted acid sites, which resulted in a decrease of the catalytic activity. This suggests that Bronsted acid sites are generated at the boundaries between tungsten oxide monolayer domains.
Kitano, Tomoyuki,Hayashi, Tomohiro,Uesaka, Toshio,Shishido, Tetsuya,Teramura, Kentaro,Tanaka, Tsunehiro
p. 2011 - 2020
(2014/08/05)

Synthesis of terpinyl acetate using octadecylamine ethoxylate ionic liquids as catalysts
Terpinyl acetate, an important natural flavor, can be synthesized by esterification of α-pinene with acetic acid under acidic conditions. In this work, seven acidic ionic liquids were first synthesized, using octadecylamine ethoxylates (AC 1810, AC 1815, AC 1820, and AC 1830) as the cations, and characterized by FT-IR, 1H NMR, and 13C NMR spectroscopy. The ionic liquids were then used as catalysts in the synthesis of terpinyl acetate. The effect of preparation conditions on catalyst performance was examined. It was found that the acidic ionic liquid 1-(3-sulfonic acid)propyl-3-poly(ethylene glycol) octadecylamine polyoxyethylene ether tetrafluoroborate ([PAC1815]+[BF4]-) was an excellent catalyst for synthesis of terpinyl acetate. The effects of the conditions used for preparation of terpinyl acetate were examined in detail, and the optimum preparation conditions were obtained. Under the optimum conditions, the yield of terpinyl acetate reached 35.70 %. When the catalyst was reused for the 5th time, the yield of terpinyl acetate was still 32.00 %. The results showed that effective separation and recycling of catalyst could contribute to developing a new strategy for synthesis of terpinyl acetate.
Li, Lu,Liu, Shiwei,Shi, Yanjing,Yu, Shitao,Xie, Congxia,Qi, Chunjie
p. 2095 - 2105
(2013/06/05)

Mechanistic insights into the rhenium-catalyzed alcohol-to-olefin dehydration reaction
Rhenium-based complexes are powerful catalysts for the dehydration of various alcohols to the corresponding olefins. Here, we report on both experimental and theoretical (DFT) studies into the mechanism of the rhenium-catalyzed dehydration of alcohols to olefins in general, and the methyltrioxorhenium-catalyzed dehydration of 1-phenylethanol to styrene in particular. The experimental and theoretical studies are in good agreement, both showing the involvement of several proton transfers, and of a carbenium ion intermediate in the catalytic cycle. Ionic or concerted? Rhenium-based complexes are powerful catalysts for the dehydration of various alcohols to the corresponding olefins. Experimental and DFT studies into the mechanism of the rhenium-catalyzed dehydration of alcohols to olefins are reported. The experimental and theoretical studies are in good agreement, both showing the involvement of a carbenium ion intermediate in the catalytic cycle (see figure). Copyright
Korstanje, Ties J.,Jastrzebski, Johann T. B. H.,Kleingebbink, Robertus J. M.
p. 13224 - 13234
(2013/10/01)

Microwave-assisted α-pinene acidic catalytic isomerisation
A comparative study of microwave assisted α-pinene acidic catalytic isomerisation reactions with near-critical water procedure under microwave irradiation is presented. This study can be performed because in both cases the mechanism is similar, namely an acidiccatalyzed rearrangement. The non-critical method technique is milder using a lower temperature and pressure and a shorter reaction time than near-critical water conditions. The general aspect of the selectivity of the reaction products is changed, being higher for α-terpinolene and γ-terpinolene and lower for limonene and camphene compared to the non-critical conditions.
Szuecs-Balazs, Jozsef Zsolt,Coros, Maria,Molnar, Diana,Vlassa, Mircea
p. 209 - 213
(2013/03/13)

Supported H4SiW12O40 catalysts for α-pinene isomerization
The heterogeneous isomerization of α-pinene was studied at 100, 130 and 160°C using 10% supported H4SiW12O40 (SiW) on SiO2, TiO2 and HZSM-5. The effect of the reaction temperature and the concentratio
Szuecs-Balazs, Jozsef-Zsolt,Coros, Maria,Woiczechowski-Pop, Adrian,Blanita, Gabriela,Vlassa, Mircea
p. 1208 - 1217
(2012/11/13)

Organic reactivity of alcohols in superheated aqueous salt solutions: An overview
The low dielectric constant and high self-dissociation constant of water in a temperature range between 150 and 250 °C make it a very appealing solvent for synthesis. Surprisingly, while organic chemistry in water at low temperature or around its critical point has been investigated in detail, very little seems to be known about the behaviour of organic molecules under hydrothermal conditions. The present work thus aims at shading some light on this field. As a start, we decided to investigate the reactions in which alcohols can undergo in water in the above-mentioned temperature range. Knowing that very strong salt effects on organic reactions have already been observed in super critical water, the impact of salt on the outcome of our tests was also investigated in detail.
Avola, Sabine,Goettmann, Frederic,Antonietti, Markus,Kunz, Werner
scheme or table
p. 1568 - 1573
(2012/10/07)

Amberlyst-15: A reusable heterogeneous catalyst for the dehydration of tertiary alcohols
Tertiary alcohols react under mild conditions in the presence of Amberlyst-15 (dry) (solid-supported sulfonic acid) to give predominantly the most stable alkene in very good yield. The dehydration of tertiary alcohol functionality occurs without observation of rearrangement and polymerization products, and with outstanding substrate tolerance, which include the NHCBz, NHBoc, OSEM, OTBDMS, OBOM and ethylene ketal functional groups. Amberlyst-15 (dry) can be easily recovered from the reaction medium and reused for five cycles, maintaining the catalytic efficiency. In addition, the dehydration can occur under continuous operation.
Frija, Luís M.T.,Afonso, Carlos A.M.
scheme or table
p. 7414 - 7421
(2012/09/22)

Transformations of monoterpene hydrocarbons on ferrierite type zeolites
Transformations of α-pinene and limonene over hydrogen forms of commercial ferrierite type zeolites of different origin (Tosoh Corp. and Zeolyst Intern.) have been studied in the liquid phase at 313-363 K. The catalysts were characterized by XRD, sorption
Rachwalik,Hunger,Sulikowski
scheme or table
p. 98 - 105
(2012/07/14)

A 1,6-ring closure mechanism for (+)-δ-cadinene synthase?
Recombinant (+)-δ-cadinene synthase (DCS) from Gossypium arboreum catalyzes the metal-dependent cyclization of (E,E)-farnesyl diphosphate (FDP) to the cadinane sesquiterpene δ-cadinene, the parent hydrocarbon of cotton phytoalexins such as gossypol. In contrast to some other sesquiterpene cyclases, DCS carries out this transformation with >98% fidelity but, as a consequence, leaves no mechanistic traces of its mode of action. The formation of (+)-δ-cadinene has been shown to occur via the enzyme-bound intermediate (3R)-nerolidyl diphosphate (NDP), which in turn has been postulated to be converted to cis-germacradienyl cation after a 1,10-cyclization. A subsequent 1,3-hydride shift would then relocate the carbocation within the transient macrocycle to expedite a second cyclization that yields the cadinenyl cation with the correct cis stereochemistry found in (+)-δ-cadinene. An elegant 1,10-mechanistic pathway that avoids the formation of (3R)-NDP has also been suggested. In this alternative scenario, the final cadinenyl cation is proposed to be formed through the intermediacy of trans, trans-germacradienyl cation and germacrene D. In addition, an alternative 1,6-ring closure mechanism via the bisabolyl cation has previously been envisioned. We report here a detailed investigation of the catalytic mechanism of DCS using a variety of mechanistic probes including, among others, deuterated and fluorinated FDPs. Farnesyl diphosphate analogues with fluorine at C2 and C10 acted as inhibitors of DCS, but intriguingly, after prolonged overnight incubations, they yielded 2F-germacrene(s) and a 10F-humulene, respectively. The observed 1,10-, and to a lesser extent, 1,11-cyclization activity of DCS with these fluorinated substrates is consistent with the postulated macrocyclization mechanism(s) en route to (+)-δ-cadinene. On the other hand, mechanistic results from incubations of DCS with 6F-FPP, (2Z,6E)-FDP, neryl diphosphate, 6,7-dihydro-FDP, and NDP seem to be in better agreement with the potential involvement of the alternative biosynthetic 1,6-ring closure pathway. In particular, the strong inhibition of DCS by 6F-FDP, coupled to the exclusive bisabolyl- and terpinyl-derived product profiles observed for the DCS-catalyzed turnover of (2Z,6E)-farnesyl and neryl diphosphates, suggested the intermediacy of α-bisabolyl cation. DCS incubations with enantiomerically pure [1- 2H1](1R)-FDP revealed that the putative bisabolyl-derived 1,6-pathway proceeds through (3R)-nerolidyl diphosphate (NDP), is consistent with previous deuterium-labeling studies, and accounts for the cis stereochemistry characteristic of cadinenyl-derived sesquiterpenes. While the results reported here do not unambiguously rule in favor of 1,6- or 1,10-cyclization, they demonstrate the mechanistic versatility inherent to DCS and highlight the possible existence of multiple mechanistic pathways.
Faraldos, Juan A.,Miller, David J.,Gonzalez, Veronica,Yoosuf-Aly, Zulfa,Cascon, Oscar,Li, Amang,Allemann, Rudolf K.
supporting information; experimental part
p. 5900 - 5908
(2012/05/07)

Isomerization of α-Pinene over Immobilized AlCl3 Catalysts
Immobilized AlCl3 catalysts supported on γ-Al2O3 and SiO2 were prepared by a two-step vapor method and their catalytic activities were evaluated by the liquid phase isomerization of α-pinene for the first time. The results showed that the immobilized AlCl3 catalyst gave excellent catalytic performance for the isomerization of α-pinene. The AlCl3/SiO2 catalyst gave 98.4% conversion of α-pinene and 93.7% selectivity for the main products such as camphene, limonene, and terpinolene at a reaction temperature of 40 °C. The AlCl3/γ-Al2O3 catalyst gave much higher activity, 95.5% conversion of α-pinene and 94.4% selectivity for the main products even at temperatures as low as 30 °C. The excellent catalytic performance of the immobilized AlCl3 catalysts is due to their strong acidity.
Wu, Yihui,Tian, Fuping,He, Min,Cai, Tianxi
p. 1138 - 1142
(2016/04/19)

An efficient microwave technique for exo- to endo-double bond migration in natural products
A few sesquiterpene lactones and monoterpenes when subjected to microwave irradiation on solid surface undergo facile carbon-carbon double bond migration from from exo- to endo-position.
Kaur, Damandeep,Setia,Chahal,Chhabra
experimental part
p. 611 - 614
(2011/06/21)

α-Pinene isomerisation over heteropoly acid catalysts in the gas-phase
The isomerisation of α-pinene was studied in the gas phase over solid heteropoly acid (HPA) catalysts in a fixed-bed continuous flow reactor at 200 °C and ambient pressure. The catalysts included bulk and SiO 2-supported H3PW12O40 and bulk Cs2.5H0.5PW12O40 possessing strong Br?nsted acid sites, as well as composites prepared by supporting 15 wt% H3PW12O40 on Nb2O5, ZrO2 and TiO2 possessing both Br?nsted and Lewis acid sites of moderate strength. The reaction yielded camphene as the main product in a mixture with monoterpene by-products such as limonene, terpinolenes, terpinenes, β-pinene, p-cymene and others. The HPA catalysts with strong Br?nsted acid sites exhibited high initial activities, but suffered from catalyst deactivation, resulting in low camphene yields. Conversely, the HPA catalysts supported on Nb2O5, ZrO 2 and TiO2, although weaker acids, showed more stable performance in α-pinene isomerisation. The HPA catalyst supported on TiO2 gave a camphene yield of 51% and a total camphene and limonene yield of 58%.
Alsalme, Ali,Kozhevnikova, Elena F.,Kozhevnikov, Ivan V.
experimental part
p. 219 - 224
(2011/12/15)

Methoxylation of α-pinene over heteropolyacids immobilized in silica
The methoxylation of α-pinene was studied using heteropolyacids immobilized on silica as catalysts, at 60 °C, being the α-terpinyl methyl ether the main product. Tungstophosphoric acid (PW), molybdophosphoric acid (PMo), tungstosilicic acid (SiW) and molybdosilicic acid (SiMo) were immobilized on silica by sol-gel method. It was observed that the catalytic activity of the silica-supported heteropolyacids decreases in the series: PW2_S > SiW_S > PMo_S > SiMo_S. A series of PW immobilized on silica with different PW loading were prepared. It was observed that the catalytic activity increases with the amount of PW immobilized on silica. However, at high amount of PW on silica, a decrease of the catalytic activity was observed. Good values of selectivity to α-terpinyl methyl ether (about 60% near complete conversion) were obtained with all catalysts. Catalytic stability of the PW2_S was evaluated by performing consecutive batch runs with the same catalyst sample. After the third batch it was observed a stabilisation of the initial activity. A kinetic model was developed assuming that the α-pinene is consumed according to the parallel reaction network. It was observed that the kinetic model fits the experimental concentration data quite well.
Pito,Matos,Fonseca,Ramos,Vital,Castanheiro
body text
p. 140 - 146
(2010/10/01)

Microporous acidic cesium salt of 12-tungstosilicic acid Cs 3HSiW12O40 as a size-selective solid acid catalyst
An acidic Cs salt of H4SiW12O4O 40 (Cs3HSiW12O40), which was prepared by titrating an aqueous solution of H4SiW12O 40 with an aqueous solution of Cs2CO3, possessed only micropores and exhibited size-selective catalysis for acid-catalyzed reactions in liquid phase.
Kamiya, Yuichi,Sano, Shogo,Miura, Yu-Ki,Uchida, Yohei,Ogawa, Yuki,Iwase, Yukari,Okuhara, Toshio,Degnan Jr.
supporting information; scheme or table
p. 881 - 883
(2011/01/08)

Desilication of ZSM-5 and ZSM-12 zeolites: Impact on textural, acidic and catalytic properties
Two zeolites of different topology: ZSM-5 and ZSM-12 were subjected to desilication in the NaOH solutions of increasing concentrations. Changes in the properties of modified zeolites were investigated by several methods ( 29Si and 27
Gil, Barbara,Mokrzycki, ?ukasz,Sulikowski, Bogdan,Olejniczak, Zbigniew,Walas, Stanis?aw
experimental part
p. 24 - 32
(2010/10/19)

Fate of monoterpenes in near-critical water and supercritical alcohols assisted by microwave irradiation
The rearrangement of α- and β-pinene was studied under microwave irradiation in near-critical water and supercritical lower aliphatic alcohols, with the aim of identifying the pathway of α- and β-pinene isomerization. Generally, two pathways occur, pyroly
Szuppa, Tony,Stolle, Achim,Ondruschka, Bernd
experimental part
p. 1560 - 1567
(2010/07/04)

On the isolation of neat allylic fluorides
Neat cinnamyl fluoride, geranyl fluoride, 5-carbomethoxy-3-fluorocyclohexene and parent 3-fluorocyclohexene undergo spontaneous decomposition on contact with borosilicate glass or catalytic quantities of moderately strong acids that consists in polycondensation with elimination of HF initiated by electrophilic abstraction of F-. Acid sensitivity of these allylic fluorides correlates with stability of respective allylic cations, exceeds that of parent benzyl fluoride, yet can be mitigated by the use of Teflon and PFA containers that permit their isolation and handling in the neat state.
Lee, Eunsung,Yandulov, Dmitry V.
experimental part
p. 474 - 483
(2009/12/06)