- 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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- M -C2B10H11HgCl/AgOTf-Catalyzed Reaction for Reductive Deoxygenation
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A m -C2B10H11HgCl/AgOTf-catalyzed reaction of allyl silyl ethers with N -Boc- N ′-tosylhydrazine has been developed. Under mild conditions, the resulting allyl hydrazine products were transformed into naked alkenes in good yield. Furthermore, the used m -C2B10H11HgCl could be recovered quantitatively.
- Yamasaki, Naoto,Kanno, Marina,Sakamoto, Kyohei,Kasai, Yusuke,Imagawa, Hiroshi,Yamamoto, Hirofumi
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p. 169 - 175
(2018/03/26)
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- Radical chain reduction of alkylboron compounds with catechols
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The conversion of alkylboranes to the corresponding alkanes is classically per-formed via protonolysis of alkylboranes. This simple reaction requires the use of severe reaction conditions, that is, treatment with a carboxylic acid at high temperature (>150 °C). We report here a mild radical procedure for the transformation of organoboranes to alkanes. 4-tert-Butylcatechol, a well-established radical inhibitor and antioxidant, is acting as a source of hydrogen atoms. An efficient chain reaction is observed due to the exceptional reactivity of phenoxyl radicals toward alkylboranes. The reaction has been applied to a wide range of organoboron derivatives such as B- alkylcatecholboranes, trialkylboranes, pinacolboronates, and alkylboronic acids. Furthermore, the so far elusive rate constants for the hydrogen transfer between secondary alkyl radical and catechol derivatives have been experimentally determined. Interestingly, they are less than 1 order of magnitude slower than that of tin hydride at 80 °C, making catechols particularly attractive for a wide range of transformations involving C-C bond formation.
- Villa, Giorgio,Povie, Guillaume,Renaud, Philippe
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p. 5913 - 5920
(2011/06/16)
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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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- O-DPPB-directed copper-mediated and -Catalyzed allylic substitution with grignard reagents
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The ortho-diphenylphosphanylbenzoyl (o-DPPB) group was explored as a directing leaving group in copper-mediated and copper-catalyzed allylic substitution with Grignard reagents. Complete control of chemo-, regio- and stereoselectivity with complete syn-1,3-chirality transfer was observed as a result of the directed nature of the reaction. No excess of or ganometallic reagent is required and the directing group can be recovered quantitatively. Coordination studies in the solid state and in solution have shown that two substrates are bound via the phosphine function of the directing group at copper. Dynamic NMR experiments in solution are in agreement with a ligand-exchange process at copper, a prerequisite for the development of a substoichiometric process.
- Demel, Peter,Keller, Manfred,Breit, Bernhard
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p. 6669 - 6683
(2008/09/16)
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- Copper-Mediated and -Catalyzed o-DPPB-Directed Allylic Substitution
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Complete control of chemo-, regio- and stereoselectivity in the course of copper-catalyzed and -mediated allylic substitution could be obtained with me ortho-diphenylphosphanyl (o-DPPB) function as a reagent-directing leaving group. Complete chirality transfer by way of a syn-addition process has been achieved for cyclic and acyclic systems. Readily available Grignard reagents may be employed as nucleophiles and the directing o-DPPB group can be recovered quantitatively. The reaction requires neither cooling nor an excess of organometallic reagent.
- Breit, Bernhard,Demel, Peter
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p. 429 - 432
(2007/10/03)
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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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- ALYLATION OF ALLYLIC CYCLOHEXENYL ESTERS WITH TRIALKYLALUMINIUM REAGENTS. A REGIO AND STEREOCHEMICAL STUDY
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Regio and stereochemistry of the title reaction appear to be strongly influenced by the nature of both organometallic and allylic reagents.The results are discussed in view of the intervention of ion-pair intermediates.
- Gallina, C.
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p. 519 - 522
(2007/10/02)
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- REGIO AND STEREOSPECIFIC SYNTHESIS OF CIS AND TRANS 3-METHYL-6-METHYLETHYL CYCLOHEXENES AND 3-METHYL-4-METHYLETHYLCYCLOHEXENES. REACTIONS OF ALLYLIC ACETATES AND CARBAMATES WITH Li2Cu3Me5 AND LiCuMe2
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The isomeric alkenes 1-4 have been obtained by syn, γ substitution of the appropriate allylic carbamates with Li2Cu3Me5.The behaviour of carbamates is deeply affected by the nature of the copper reagent.
- Gallina, C.
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p. 3093 - 3096
(2007/10/02)
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- A TRICYCLIC TERPENE HYDROCARBON - CYCLOPINENE
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The reduction of the tosylate of filipendulol (2,7,7-trimethylbicyclohept-2-en-6-ol) with lithium tetrahydroaluminate in ether has given a hydrocarbon (I), C10H16 (bp 66.5 deg C/50 mm, n20D 1.4565, d2020 0.8599, 19D -104.5 deg.NMR: 0.69 ppm (CH3); 0.95 ppm, (CH3); 1.17 ppm (CH3); no signals of olefinic protons.IR: 3054 cm-1 (three-membered ring with gem-protons); 1363 and 1387 cm-1 (gem-CH3), absorption bands of multiple bonds absent.Heating (70 deg C) (I) with a sulfonated cation-exchange resin in hexane gave α-pinene.The hydrogenation of (I) over PtO2 in acetic acid gave pinane.The most probable structure of (I) is 2,7,7-trimethyltricyclo2,4>heptane.The substance has been called cyclopinene.
- Dembitskii, A. D.,Yurina, R. A.,Goryaev, M. I.
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p. 671 - 673
(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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