- 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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- STRONGLY LEWIS ACIDIC METAL-ORGANIC FRAMEWORKS FOR CONTINUOUS FLOW CATALYSIS
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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; 0170
(2021/02/26)
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- Synthesis of isobenzofuran derivatives from renewable 2-carene over halloysite nanotubes
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Condensation of a terpene 2-carene with 4-methoxybenzaldehyde over a range of acid aluminosilicates including halloysite nanotubes (HNT) was studied for as a model for preparation of isobenzofuran derivatives with a pharmaceutical potential. The catalysts were characterized by FTIR with pyridine, UV by adsorption of 2-phenylethylamine from the aqueous phase, SEM, TEM and N2 physisorption. The largest selectivity to the desired product (ca. 70%) over halloysite nanotubes is associated with weak acidity of these catalysts (45 μmol/g), allowing avoiding side isomerization and condensation reactions. Moreover, the highest yield on air-dry HNT clearly indicates that weak Br?nsted sites favored the reaction. On the contrary, over strong Br?nsted and Lewis acids (Amberlyst-15, scandium triflate), the yield of isobenzofurans did not exceed 16% with formation of mainly 2-carene isomerization products. DFT calculations showed that interactions of the aldehyde with cyclopropane moiety of 2-carene giving isobenzofurans are more beneficial than an alternative direct attack of a proton, leading to side reactions. A possibility to reuse of HNT catalyst was confirmed. Overall, halloysite is a highly effective catalyst for production of isobenzofuran compounds based on 2-carene.
- Agabekov, V. E.,Aho, A.,Il'ina, I. V.,Korchagina, D. V.,Kravtsova, A. V.,Li-Zhulanov, N. S.,M?ki-Arvela, P.,Murzin, D. Yu.,Salakhutdinov, N. F.,Sandberg, T.,Sidorenko, A. Yu.,Volcho, K. P.
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- Heterogeneously Catalysed Oxidative Dehydrogenation of Menthol in a Fixed-Bed Reactor in the Gas Phase
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For the first time, the oxidative dehydrogenation of (?)-menthol to (?)-menthone and (+)-isomenthone in a marketable quality was carried out in a continuous gas phase reactor as a sustainable process using molecular oxygen as green oxidant and solid catalysts which do not contaminate the product mixture and which are easily to remove. The diastereomeric purity remained largely unchanged. Three types of catalysts were found to be very active and selective in the formation of menthone and isomenthone: AgSr/SiO2, CuO distributed on a basic support and RuMnCe/CeO2, where Ru, Mn and Ce exist in an oxidized state. The best overall yield of menthon/isomenthone obtained with an Ag-based catalyst was 58 % at 64 % selectivity, with a Cu-based catalyst 41 % at 51 % selectivity and with a Ru-based catalyst 68 % at 73 % selectivity. Reaction conditions were widely optimized.
- Kulik, Anna,Neubauer, Katja,Eckelt, Reinhard,Bartling, Stephan,Panten, Johannes,K?ckritz, Angela
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p. 1066 - 1075
(2019/06/24)
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- Metal vapor synthesis of ultrasmall Pd nanoparticles functionalized with N-heterocyclic carbenes
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The synthesis of N-heterocyclic carbene (NHC)-stabilized palladium nanoparticles (PdNPs) by an entirely new strategy comprising the NHC functionalization of ligand-free PdNPs obtained by metal vapor synthesis is described. Detailed characterization confirms the formation of very small monodisperse PdNPs (2.3 nm) and the presence of the NHC ligand on the Pd surface. The stable NHC-functionalized PdNPs dispersed onto a carbon support showed high activity in the hydrogenation of limonene with enhanced regioselectivity in comparison to bare PdNPs on carbon.
- Tegeder, Patricia,Marelli, Marcello,Freitag, Matthias,Polito, Laura,Lamping, Sebastian,Psaro, Rinaldo,Glorius, Frank,Ravoo, Bart Jan,Evangelisti, Claudio
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supporting information
p. 12647 - 12651
(2018/09/27)
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- Structural, electronic and catalytic properties of palladium nanoparticles supported on poly(ionic liquid)
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The structural, electronic and support effect on palladium nanoparticles (Pd NPs) prepared by sputtering deposition and chemical reduction of a Pd(II) precursor in/on a poly(ionic liquid) (PIL) was investigated in the selective hydrogenation of α,β-unsaturated carbonyl compounds and dienes. Sputtering deposition generates naked NPs with a narrow size distribution (3.2–3.8 nm) that are predominantly composed of Pd(0) (85–100%). Conversely, chemical reduction produces PIL-covered NPs with almost twice the average size (6.6 nm) and only 15% Pd(0). Regard the catalytic performance, support composition (by ionic liquid (IL) addition or not) and NP location are decisive. The best activity and selectivity was obtained with imprinted Pd NPs on a PIL/IL mixture (D-MPIL.NTf2/IL-Pd catalyst). A kinetic investigation was conducted using 2-cyclohexen-1-one (CHN) and D-MPIL.NTf2/IL-Pd catalyst revealing that this reaction follows the Langmuir-Hinshelwood mechanism. Enthalpies obtaining from a Van't Hoff plot show that the adsorption of the CHN substrate on the surface of the PIL-Pd catalyst is an exothermic process (-9 kJ mol?1), whereas H2 adsorption occurs by an endothermic process (12 kJ mol?1). This distinct behavior is consistent with the rate determining step proposed, in which the independent adsorption of reagents is followed by the hydrogenation of a π-allyl intermediate on the catalyst surface.
- Simon, Nathália M.,Abarca, Gabriel,Scholten, Jackson D.,Domingos, Josiel B.,Mecerreyes, David,Dupont, Jairton
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- Revealing Hydrogenation Reaction Pathways on Naked Gold Nanoparticles
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Gold nanoparticles (AuNPs) display distinct characteristics as hydrogenation catalysts, with higher selectivity and lower catalytic activity than group 8-10 metals. The ability of AuNPs to chemisorb/activate simple molecules is limited by the low coordination number of the surface sites. Understanding the distinct pathways involved in the hydrogenation reactions promoted by supported AuNPs is crucial for broadening their potential catalytic applications. In this study, we demonstrate that the mechanism of the hydrogenation reactions catalyzed by AuNPs with "clean" surfaces may proceed via homolytic or heterolytic hydrogen activation depending on the nature of the support. The synthesis of naked AuNPs employing γ-Al2O3 and ionic liquid (IL)-hybrid γ-Al2O3 supports was accomplished by sputtering deposition using ultrapure gold foils. This highly reproducible and straightforward procedure furnishes small (~6.6 nm) and well-distributed metallic gold nanoparticles (Au(0)NPs) that are found to be active catalysts for the partial and selective hydrogenation of substituted conjugated dienes, alkynes, and α,β-unsaturated carbonyl compounds (aldehydes and ketones). Kinetic and deuterium labeling studies indicate that heterolytic hydrogen activation is the primary pathway occurring on the AuNPs imprinted directly on γ-Al2O3. In contrast, AuNPs supported on IL-hybrid γ-Al2O3 materials cause the reaction to proceed via a homolytic hydrogen activation pathway. The IL layer surrounds the AuNPs and acts as a cage, influencing the frequency of the interaction of the catalytically active species and the metal surface and, consequently, the catalytic performance of the AuNPs. The IL layer is shown to improve the product selectivity by the enhancement of the substrate/product discrimination, and to decrease the catalytic activity by shifting the rate-determining step to the H2 and substrate competitive adsorption/activation on the same active sites. A series of kinetic experiments suggest that AuNPs imprinted on an IL-hybrid γ-Al2O3 support are more efficient (lower activation energy, Ea) than group 8-10 metal based catalysts for hydrogenation reactions at moderate to high temperatures (75-150 °C).
- Luza, Leandro,Rambor, Camila P.,Gual, Aitor,Alves Fernandes, Jesum,Eberhardt, Dario,Dupont, Jairton
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p. 2791 - 2799
(2017/05/31)
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- Hybrid catalysts based on platinum and palladium nanoparticles for the hydrogenation of terpenes under slurry conditions
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Catalysts based on platinum and palladium nanoparticles immobilized in mesoporous phenolformaldehyde polymers modified with sulfo groups have been used for the hydrogenation of a number of terpenes, such as (S)-(–)-limonene, α-terpinene, γ-terpinene, and terpinolene. It has been found that Pd-containing catalysts exhibit higher activity in the exhaustive hydrogenation of terpenes, whereas Pt-containing catalysts have high selectivity for p-menthene.
- Karakhanov,Boronoev,Subbotina,Zolotukhina,Maximov,Filippova, T. Yu.
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p. 1114 - 1122
(2017/02/15)
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- Supercritical fluid deposition of Ru nanoparticles onto SiO2 SBA-15 as a sustainable method to prepare selective hydrogenation catalysts
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Ru nanoparticles were successfully deposited onto mesoporous SiO2 SBA-15 using supercritical CO2 (scCO2). The use of scCO2 favoured the metal dispersion and Ru nanoparticles uniformly distributed throughout the support were obtained. Different precursors and methodologies were employed: impregnation with Ru(tmhd)2(COD) in scCO2 at 80°C and 13.5 and 19.3 MPa and further reduction in H2/N2 at 400°C at low pressure, reactive deposition of Ru(tmhd)2(COD) with H2 in scCO2 at 150°C and reactive deposition of RuCl3·xH2O with ethanol in scCO2 at 150 and 200°C. The size of the particles was limited in one dimension by the pore size of the support. The metal loading varied with the methodology and experimental conditions from 0.9 to 7.4% Ru mol. These materials exhibited remarkable catalytic activity. The Ru/SiO2 SBA-15 materials prepared by reactive deposition with H2 in scCO2 were selective catalysts for the hydrogenation reactions of benzene and limonene, allowing the production of partly hydrogenated hydrocarbons that may serve as building blocks for more complex chemicals. scCO2 is shown to be a green solvent that allows the preparation of efficient heterogeneous catalysts to design sustainable processes. Furthermore, in the hydrogenation of limonene, scCO2 was also used as the solvent.
- Morère,Torralvo,Pando,Renuncio,Caba?as
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p. 38880 - 38891
(2015/05/20)
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- Selective carvone hydrogenation to dihydrocarvone over titania supported gold catalyst
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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
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p. 189 - 194
(2015/03/14)
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- Heteroatom-free arene-cobalt and arene-iron catalysts for hydrogenations
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75 years after the discovery of hydroformylation, cobalt catalysts are now undergoing a renaissance in hydrogenation reactions. We have evaluated arene metalates in which the low-valent metal species is - conceptually different from heteroatom-based ligands - stabilized by π coordination to hydrocarbons. Potassium bis(anthracene)cobaltate 1 and -ferrate 2 can be viewed as synthetic precursors of quasi-"naked" anionic metal species; their aggregation is effectively impeded by (labile) coordination to the various π acceptors present in the hydrogenation reactions of unsaturated molecules (alkenes, arenes, carbonyl compounds). Kinetic studies, NMR spectroscopy, and poisoning studies of alkene hydrogenations support the formation of a homogeneous catalyst derived from 1 which is stabilized by the coordination of alkenes. This catalyst concept complements the use of complexes with heteroatom donor ligands for reductive processes. Especially high selectivities were observed in the hydrogenation of various alkenes, ketones, and imines with bis(anthracene) cobaltate(-I) [K(dme)2{Co(C14H10)2}] under mild conditions (1-5 mol% cat., 1-10 bar H2, 20-60°C). Mechanistic studies indicate the operation in alkene hydrogenations of a homogeneous catalyst formed by initial ligand exchange and stabilized by the coordination of π-acidic alkenes or arenes.
- Gaertner, Dominik,Welther, Alice,Rad, Babak Rezaei,Wolf, Robert,Von Wangelin, Axel Jacobi
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supporting information
p. 3722 - 3726
(2014/04/17)
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- NOVEL ALICYCLIC ALCOHOL
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Provided is an alicyclic alcohol compound which can be used as a raw material for a compound perfume, and which has excellent floral-green like aromas which are crisp and fresh; also provided are a manufacturing method for the same, and a perfume composition which contains the alicyclic alcohol compound. An alicyclic alcohol compound having a specified structure represented by chemical formula (1) has excellent floral-green-like aromas which are crisp and fresh; and a method for manufacturing the alicyclic alcohol compound represented by chemical formula (1) by reacting, in the presence of hydrogen fluoride, 1-isopropyl-4-methylcyclohexene and carbon monoxide, reacting the resulting 4-isopropyl-1-methylcyclohexane carboxylic acid fluoride with alcohol, and, after having acquired a cyclohexane carbonyl compound, reducing the cyclohexane carbonyl compound.
- -
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Paragraph 0052-0053
(2013/11/19)
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- Cyclization of citronellal in a supercritical solvent in a flow reactor in the presence of Al2O3
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The reactivity of citronellal under supercritical solvent conditions in a flow reactor in the presence of Al2O3 is examined. It is shown that at 160°C, the main transformation product of citronellal is isopulegol, and when the temperature is increased to 190°C, they are monoterpenes with a para-menthane framework and myrcene. Pleiades Publishing, Ltd., 2012.
- Anikeev,Il'Ina,Volcho,Salakhutdinov
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p. 1917 - 1919
(2013/01/15)
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- Reaction of menthol and phenol in the presence of aluminium alkoxides
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Phenol was alkylated with menthol in the presence of organoaluminium catalysts such as aluminium phenoxide and aluminium isopropoxide. Reaction products were isolated and characterized. Certain features of the process were determined.
- Chukicheva,Fedorova,Koroleva,Kuchin
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experimental part
p. 450 - 454
(2009/04/11)
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- Fragmentation of menthyl- and neomenthyloxychlorocarbenes: Elimination and substitution reactions of alicyclic oxychlorocarbenes
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Fragmentations of menthyloxychlorocarbene (5) and neomenthyloxychlorocarbene (6) follow distinct pathways to (largely) stereochemically retained substitution products from 5 and elimination products from 6, closely resembling the product distributions from deaminations of the corresponding menthyl- and neomenthylamines.
- Moss, Robert A.,Johnson, Lauren A.,Kacprzynski, Monica,Sauers, Ronald R.
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p. 5114 - 5118
(2007/10/03)
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- Chemoselective reductive deoxygenation of α,β-unsaturated ketones and allyl alcohols
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A simple and convenient procedure for a highly chemoselective reductive deoxygenation of α,β-unsaturated ketones and allyl alcohols to olefins by sodium cyanoborohydride and boron trifluoride etherate in dry THF is described.
- Srikrishna, Adusumilli,Viswajanani, Ranganathan,Sattigeri, Jitendra A.,Yelamaggad, Channabasaveshwar V.
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p. 2347 - 2350
(2007/10/02)
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- Dehydration of secondary alcohols via thermolysis of in situ generated alkyl diphenyl phosphates: An inexpensive and environmentally compatible method for the preparation of alkenes
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Secondary alcohols are converted into diphenyl phosphate esters by the action of triphenyl phosphate or diphenyl phosphorochloridate in high-boiling, water-miscible solvents in the presence of base. The alkyl diphenyl phosphates undergo thermolysis to afford high yields of alkenes which distill from the reaction mixtures. Purification of the products is achieved by extraction with dilute sulfuric acid which removes traces of solvent and base that may have codistilled. The ratios of 2- (14) and 3-menthene (15), obtained from menthol (13) and neomenthol (16), and the formation of rearranged alkenes by 1,2-shifts from 3, 6, and 3,3-dimethylbutan-2-ol are consistent with ionic intermediates of the elimination reaction. The novel dehydration method offers distinct and important advantages over the existing methods.
- Quast,Dietz
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p. 1300 - 1304
(2007/10/02)
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- Composition of Mixtures of Hydrocarbons after BIRCH-Reduction of Substituted Benzenes and Acid Catalyzed Addition of Alcohols to Alkylsubstituted Cyclohexenes and Carbohexa-1,4-dienes
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10 different benzene hydrocarbons 1, indane, tetraline, anisol and phenol are reduced by sodium in liquid ammonia in the presence of methanol to the BIRCH products 2.The product mixture compositions are determined through capillary GLC.On storage at +6 deg C some rearomatization of the 1,4-cyclohexadienes 2 occurs.Data of the 1H- and 13C-.n.m.r. spectra and also mass spectra of the BIRCH 1,4-dienes 2 are given.For comparison 4-alkoxycyclohexenes 4 and 1-alkoxy-1-methylcyclohexanes 8 are prepared and spectroscopically characterized.Acid-catalyzed addition of alcohols to the 1,4-cyclohexadienes systems is a slow process and gives the 4-alkoxy-4-alkylcyclohex-1-enes (4) only in moderate yields up to 30percent.Most of the products are dimers 5 and also oligomers 6 of the parent hydrocarbons 2.
- Beger, J.,Thomas, B.,Vogel, T.,Kirmse, K.,Lang, R.
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p. 481 - 488
(2007/10/02)
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- HYDROGENATION OF PINENES AND m- AND p-MENTHENES UNDER CONJUGATED HYDROGENATION-DEHYDROGENATION REACTION CONDITIONS
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Hydrogenation of pinenes and m- and p-menthenes under conjugated hydrogenation-dehydrogenation reaction conditions proceeds with the formation of cis- and trans-isomers with the predominance of the thermodynamically more stable isomer.The conjugated hydrogenatio-dehydrogenation of (-)-β-pinene can be used for obtaining (-)-α-pinene on a preparative scale, and of dipentene - for obtaining 1-p-menthene.
- Kalechits, G. V.
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p. 1311 - 1314
(2007/10/02)
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- Nucleophilic Reactions of Acetals, Alkyl Sulfonates, and Oxiranes with Diisobutylaluminum Benzenetellurolate
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Diisobutylaluminum benzenetellurolate was proved to be an effective nucleophilic reagent toward acetals, alkyl sulfonates, and oxiranes to give the corresponding tellurides.These reactions showed the characteristics of an SN2 type.When the substitution reactions were sterically hindered, olefins and allylic alcohols were obtained from alkyl sulfonates and oxiranes, respectively.
- Sasaki, Kazuaki,Mori, Toshiharu,Doi, Yoshitaka,Kawachi, Akinori,Aso, Yoshio,et al.
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p. 415 - 418
(2007/10/02)
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- Photochemical Transformations VI: Organic Iodides (Part 5) - Templet Effect of Transition Metal Ions on Photocyclization of Some Olefinic Acyclic Terpene Iodides
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Photocyclization of citronellyl iodide in the presence of certain transition metal salts especially CuCl, results in a significant increase (from 16percent to 35percent) in the yield of the cyclization products.Similar results have been obtained with geranyl and neryl iodides (11, 17).This enhancement of cyclization/elimination ratio is sought to be explained in terms of a templet effect of the transition metal ion.
- Subbarao, Kanury V.,Damodaran, N. P.,Dev, Sukh
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p. 1008 - 1011
(2007/10/02)
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- REACTIONS OF p-TOLUENESULFONIC ACID TERPENE DERIVATIVES WITH LITHIUM IN ETHYLAMINE
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Reactions of terpene p-toluenesulfonamides and p-toluenesulfonates with lithium in ethylamine were stated to afford, exclusively or mainly, respective amines and alcohols as the result of N-S or O-S bond cleavage.Presence of hydroxyl groups is not a hindrance. 2α-Hydroxy-3α-tosyloxypinane undergoes, partially, a rearrangement.The mechanism of that reaction is discussed.
- Rykowski, Zbigniew,Gubrynowicz, Olaf,Wrzesien, Justyna
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p. 1237 - 1244
(2007/10/02)
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- INVESTIGATION OF COMPOUNDS OF THE MENTHANE SERIES. XVI. REDUCTION OF o- AND p-ISOPROPENYLTOLUENES WITH CALCIUM HEXAAMMONIATE
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In the reduction of o- and p-isopropenyltoluenes with calcium hexaammoniate in the presence of protic and aprotic solvents 1,2-addition of hydrogen mostly occurs with the formation of o- and p-cymenes and o- and p-menthatrienes, which under the reaction conditions give the products from 1,2- and 1,4-addition of hydrogen.
- Bazyl'chik, V. V.
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p. 1847 - 1851
(2007/10/02)
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- PHOTOCHEMICAL TRANSFORMATIONS-II ORGANIC IODIDES-II: CITRONELLYL IODIDE, 2,3-DIHYDRO-6(Z)-FARNESYL AND 2,3-DIHYDRO-6(E)-FARNESYL IODIDES
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Experimental parameters governing ?-electrons participation during photolysis of citronellyl iodide have been investigated.Photoproducts resulting from irradiation of 2,3-dihydro-6(Z)- and 2,3-dihydo-6(E)-farnesyl iodides have been characterised.
- Saplay, K. M.,Sahni, Ranjana,Damodaran, N. P.,Dev, Sukh
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p. 1455 - 1461
(2007/10/02)
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- Hydrogen Participation vs. Elimination. The Role and Fate of Neighboring Hydrogen in Solvolysis of Neomenthyl Tosylate
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Product composition and α-d1 and β-d3 isotope effects in the solvolysis of neomenthyl tosylate (8-OTs) were determined in 70 percent aqueous trifluoroethanol and 70 percent aqueous ethanol.Both trifluoroethanolysis and ethanolysis gave 1-2 percent neomenthol (97percent d3), 12-13percent cis-4-menthanol (100percent d3), 2-3percent trans-4-menthanol (100percent d3), 66-70percent 3-p-menthene (83percent d3 and 17percent d2), and 5-9percent 4,8-p-menthene (97percent d3), respectively.These results and the high value of the β-d3 isotope effect (kH/kD=2.45) were interpreted in terms of rate-determining hydride shift followed by elimination which accounts for 75percent of all products.In 85percent of the elimination productsthe migrating hydrogen (deuterium) is not the one being eliminated.
- Hirsl-Starcevic, Sanja,Majerski, Zdenko,Sunko, Dionis E.
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p. 3388 - 3393
(2007/10/02)
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- Hydrogenation process for the selective preparation of 3-menthene
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Non-conjugated para-menthadienes having one site of unsaturation at the 4(8)- or 8-position are hydrogenated to selectively form 3-menthene in the presence of a homogeneous ruthenium catalyst complex.
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- Terpene hydroxysulfonic acids and corresponding hydroxysulfonate salts
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Optically active terpene hydroxysulfonate salts are made by sulfonating an optically active terpene epoxide of the p-menthane family, with a sulfonating agent selected from a sulfite, a bisulfite, or a thiosulfate.
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