- DOUBLE BOND MIGRATION OVER SOLID KOH SUSPENDED IN APROTIC SOLVENTS
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KOH suspended in DME is a good reagent to effect olefin double bond migration, especially deconjugation of α-enones.
- D'Incan, E.,Viout, P.
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Read Online
- Method of preparing L-menthone from R-citronellal
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The invention discloses a method of preparing L-menthone from R-citronellal. Under the action of a Pd-Co-MOF-MMT catalyst, R-citronellal carries out heterogeneous catalytic reactions to generate L-menthone, the conversion rate of R-citronellal can reach 90-99.9%, the yield of L-menthone can reach 85-98%, and the ee value of menthone can reach 95-99.99%.
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Paragraph 0093-0094
(2020/04/06)
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- Copper Nanoparticles Immobilized on Nanocellulose: A Novel and Efficient Heterogeneous Catalyst for Controlled and Selective Oxidation of Sulfides and Alcohols
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In this work, we have described the versatility of low metal loading copper nanoparticles immobilized on nanocellulose for the controlled and selective oxidation of sulfides to sulfoxides and primary alcohols to aldehydes using green oxidant at room temperature. Aromatic, aliphatic and heterocyclic sulfides were oxidized to their corresponding sulfoxides with high yields without formation of over oxidized sulfones. Similarly, benzylic, allylic and aliphatic alcohols were selectively oxidized to aldehydes without traces of carboxylic acids in good to excellent yields.
- Dutta, Apurba,Chetia, Mitali,Ali, Abdul A.,Bordoloi, Ankur,Gehlot, Praveen S.,Kumar, Arvind,Sarma, Diganta
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p. 141 - 150
(2018/12/13)
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- Chemoenzymatic Synthesis of the Intermediates in the Peppermint Monoterpenoid Biosynthetic Pathway
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A chemoenzymatic approach providing access to all four intermediates in the peppermint biosynthetic pathway between limonene and menthone/isomenthone, including noncommercially available intermediates (-)-trans-isopiperitenol (2), (-)-isopiperitenone (3), and (+)-cis-isopulegone (4), is described. Oxidation of (+)-isopulegol (13) followed by enolate selenation and oxidative elimination steps provides (-)-isopiperitenone (3). A chemical reduction and separation route from (3) provides both native (-)-trans-isopiperitenol (2) and isomer (-)-cis-isopiperitenol (18), while enzymatic conjugate reduction of (-)-isopiperitenone (3) with IPR [(-)-isopiperitenone reductase)] provides (+)-cis-isopulegone (4). This undergoes facile base-mediated chemical epimerization to (+)-pulegone (5), which is subsequently shown to be a substrate for NtDBR (Nicotiana tabacum double-bond reductase) to afford (-)-menthone (7) and (+)-isomenthone (8).
- Cheallaigh, Aisling Ní,Mansell, David J.,Toogood, Helen S.,Tait, Shirley,Lygidakis, Antonios,Scrutton, Nigel S.,Gardiner, John M.
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p. 1546 - 1552
(2018/08/04)
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- METHOD FOR PREPARING MENTHONE FROM ISOPULEGOL
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The present invention relates to a method for preparing menthone, starting from isopulegol, using specific homogeneous catalysts.
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Paragraph 0094
(2014/03/25)
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- Gold nanoparticles supported on magnesium oxide as catalysts for the aerobic oxidation of alcohols under alkali-free conditions
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Gold nanoparticles supported on magnesium oxide were shown to be efficient heterogeneous catalysts for the liquid-phase oxidation of a wide range of alcohols using molecular oxygen as a sole oxidant in the absence of co-catalysts or additives. The Au/MgO material was prepared through the deposition- precipitation method and characterized by XRD, XPS, XAS, HRTEM, UV-Vis spectroscopy, and N2 adsorption techniques. The formation of gold nanoparticles on the MgO surface under temperature programmed reduction was monitored by in situ UV-Vis-Mass spectroscopy. Various carbonylic monoterpenoids important for fragrance and pharmaceutical industries were obtained in good to excellent yields starting from biomass-based monoterpenic alcohols, such as isoborneol, perillyl alcohol, and carveol. The Au/MgO catalyst also performs a selective one-pot oxidative esterification of benzyl alcohol in alkali-free methanol solutions in the absence of any additive to give methyl benzoate in a virtually quantitative yield.
- Costa, Vinicius V.,Estrada, Miguel,Demidova, Yulia,Prosvirin, Igor,Kriventsov, Vladimir,Cotta, Rafaela F.,Fuentes, Sergio,Simakov, Andrey,Gusevskaya, Elena V.
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experimental part
p. 148 - 156
(2012/10/07)
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- Applications of a high performance platinum nanocatalyst for the oxidation of alcohols in water
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Nanoparticles of platinum (NP-Pt), have been synthesized by supporting high nuclearity anionic carbonyl cluster (Chini cluster) on a water soluble anion exchanger, and the performance of this material, 1, as an oxidation catalyst for alcohols in water has been studied. The E-factor for the synthesis of NP-Pt by this method has been calculated and compared with that of other NP-Pt recently reported in the literature. With 1 as a catalyst, oxidations of a variety of primary and secondary alcohols by dioxygen are achieved and high turnover numbers and selectivities are obtained. The performances of 1 in the oxidation of benzyl alcohol and 1-phenylethanol are compared with those of three other platinum catalysts. These are platinum nanoparticles 2 prepared by the hydrogen reduction of [PtCl6]2- supported on the same water soluble polymer, 5% Pt on carbon, and 5% Pt on alumina, designated as 3 and 4, respectively. 1 has been found to be considerably more active than 2-4 and also other reported water soluble platinum nanocatalysts. After many turnovers (~1000 and ~165 for benzyl alcohol and 1-phenyl ethanol, respectively) partial deactivation (~ 40%) is observed, but the deactivated catalyst can be fully regenerated by treatment with dihydrogen. The TEM data of fresh, deactivated and regenerated 1 show a correlation between the particle size and activity. A mechanism consistent with this and other experimental observations including XPS data is proposed.
- Maity, Prasenjit,Gopinath, Chinnakonda S.,Bhaduri, Sumit,Lahiri, Goutam Kumar
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experimental part
p. 554 - 561
(2010/04/23)
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- 3-Alkyl-p-menthan-3-ol derivatives: synthesis and evaluation of their physiological cooling activity
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Different 3-alkyl-p-methan-3-ol derivatives provide a strong physiological cooling effect with potential application as food and cosmetic additives. In order to investigate the influence of the chemical structure on the cooling sensation, the stereoselective syntheses of 29 different 3-alkyl-p-methan-3-ol derivatives were accomplished. All the compounds obtained are odorless and were evaluated by taste, considering two sensations: a cooling effect and bitterness. The results of this structure-activity relationship study highlight that compounds with a (1R,4S)-configuration are the isomers with the more intense cooling effect and lower bitterness. In addition, the structure of the 3-alkyl chain affected the latter properties. Increasing the chain length over two carbon atoms does not change the cooling power, but enhances the bitterness with the additional feature that the branched isomers are considerably more bitter than the linear ones. Overall, the 3-alkyl-p-menthan-3-ol isomers with the best quality in terms of high cooling power and low bitterness are (1R,4S)-3-(hydroxymethyl)-p-menthan-3-ol diastereoisomers (-)-38 and (-)-42.
- Fuganti, Claudio,Joulain, Daniel,Maggioni, Francesco,Malpezzi, Luciana,Serra, Stefano,Vecchione, Andrea
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body text
p. 2425 - 2437
(2009/04/06)
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- Oxidation of alcohols to carbonyl compounds with CrO3· SiO2 in supercritical carbon dioxide
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Supercritical carbon dioxide (scCO2) is an effective reaction medium to perform the oxidation of primary and secondary aliphatic alcohols to the corresponding carbonyl compounds with chromium trioxide supported on silica. These reactions were performed by flowing a solution of the alcohol in scCO2 through a column containing the supported reagent and recovering the product by depressurization. This method avoids the use of organic solvents and the contamination of the products with chromium species.
- Gonzalez-Nunez, Maria Elena,Mello, Rossella,Olmos, Andrea,Accrete, Rafael,Asensio, Gregorio
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p. 1039 - 1042
(2007/10/03)
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- Cyclization of citronellal to menthone and isomenthone catalyzed by Al/Fe-Pillared Clays
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The cyclization of citronellal to a mixture of menthone and isomenthone (2:1) is catalyzed by Al/Fe-Pillared Clay (Al/Fe-PILC) at 80 °C in 1,2-dichloroethane in good yield. At room temperature the products are isopulegol and neo-isopulegol, the isomer ratio depending on the reaction conditions.
- Cramarossa,Forti,Pagnoni,Vidali
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- Biosynthesis of menthofuran in Mentha x piperita: Stereoselective and mechanistic studies
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Mentha x piperita shoot tips and first leaf pair were fed with aqueous solutions of [2H2]- and [2H2]/[18O]-labeled pulegone. The essential oil was analyzed by solid phase microextraction and enantioselective multidimensional gas chromatography/mass spectrometry. After feeding experiments with labeled pulegone racemate, both labeled (S)-menthofuran and (R)-menthofuran were detectable simultaneously together with genuine (R)- menthofuran. It could be shown that both labeled pulegone enantiomers are converted by Mentha x piperita to the corresponding labeled menthofuran enantiomers, favoring the labeled analogue of the nongenuine (S)-pulegone. The oxygen in menthofuran is introduced by enzymatic oxidation of pulegone, as concluded from feeding experiments with mixed labeled [2H2]/[18O]pulegone.
- Fuchs, Sabine,Zinn, Silvia,Beck, Thomas,Mosandl, Armin
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p. 4100 - 4105
(2007/10/03)
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- Regio- and enantio-selective enolisations of cyclic ketones using chiral lithium amide bases
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Enolisations of 3-methylcyclohexanone 16, and of a trans-fused perhydroisoquinolone derivative 8, using several chiral lithium amide bases have been examined.In reactions involving a single enantiomer of the ketone 8, the use of a chiral base can result in enhancement or reversal of the normal regioselectivity of enolisation to give the enol silane derivatives 9 and 10, depending on the configuration of the base used.Similar matched and mismatched results are observed when (R)-3-methylcyclohexanone, (R)-16, is treated with either enantiomer of the chiral base 3.A new type of kinetic resolution, termed regiodivergent resolution, is observed when enolisation of the racemic ketones 8 or 16 is carried out using the chiral base 3.
- Bambridge, Kimberley,Clark, Barry P.,Simpkins, Nigel S.
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p. 2535 - 2542
(2007/10/02)
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- Reaction of isopulegol and similar alcohols with sulfuryl chloride
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The reaction of isopulegol with sulfuryl chloride (or chlorine) gives two types of products: on one hand 8-chlorocitronellal and 6-chloroisocitronellal both issued from a fragmentation pathway and, on the other hand 10-chloroisopulegol resulting from an allylic chlorination.The first process, the radical nature of which is demonstrated, is clearly favored by elevated temperatures while the second one is exclusive at 0 deg C.Homologous compounds such as p-mentha-1,8-dien-5-ols, 3-phenylisopulegol and isopulegone dioxolane give rise to one or both of these processes. --- Key Words: allylic chlorination / radical fragmentation
- Bulliard, M.,Balme, G.,Monteiro, N.,Gore, J.
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p. 222 - 231
(2007/10/02)
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- Tetramethyl-1-oxaspiro[2.5]octane
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New 4,4,5,8-tetramethyl-1-oxaspiro[2.5]octane. A process for its preparation starting from 2,2,3,6-tetramethyl-1-cyclohexanone is described. 4,4,5,8-Tetramethyl-1-oxaspiro[2.5]octane is a useful raw material for the preparation of 2,2,3,6-tetramethyl-cyclohexane-carbaldehyde, a key intermediate for the synthetis of valuable fragrance ingredients.
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- Large-Scale Preparation of Pure (+)-(1S,2R,5S)-5-Methyl-2-(1-methyl-1-phenylethyl)cyclohexanol
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A procedure is described for the preparation of (S)-(-)pulegone, (-)-1, starting from (S)-(-)citronellol, (-)-6, in a preparative scale.Compound (-)-1 can easily be converted into (+)-(1S,2R,5S)-5-methyl-2-(1-methyl-1-phenylethyl)cyclohexanol: (+)-2 by a procedure described in literature, which was simplified essentially.Now (+)-2 is accessible in larger amounts and thus is available as an efficient chiral auxiliary in stoichiometric asymmetric syntheses.
- Buschmann, Helmut,Scharf, Hans-Dieter
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p. 827 - 830
(2007/10/02)
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- TOTAL SYNTHESIS OF VARIOUS ELEMANOLIDES
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Starting with a suitable substituted divinyl cyclohexanone, eleven naturally occurring 12.8-elemanolides bearing exo-methylene or methyl groups at C-11 and differing in substitution as well as in relative configuration, have been synthesized in racemic form.An approach to elemanolides with additional oxygen functionalities is principally possible by modification of the basic concept.Methods for the oxidative generation of terpenoid exo-methylene lactone and furan units are exemplified by synthesis of menthofuran and the p-menthenolides from isopulegols.
- Friedrich, Dirk,Bohlmann, Ferdinand
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p. 1369 - 1392
(2007/10/02)
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- Oxidation of Alcohols with Potassium Chlorochromate
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Potassium chlorochromate, KCrClO3, (KCC) is a versatile and inexpensive oxidation reagent.It converts secondary saturated, as well as allylic and benzylic alcohols to the corresponding carbonyl compounds in high yields in a variety of solvents, preferentially acetone.The reagent is highly selective.Thus, oxidation of primary alcohols gives aldehydes as the exclusive products.KCC is less useful for the transformation of primary saturated and homoallylic alcohols.Double bonds are susceptible to isomerization under the reaction conditions employed; for example, oxidati on of pure nerol yields citral, and pulegol is converted to a mixture of pulegone and isopulegone.Oxidation of tertiary allylic alcohols may give the transposed aldehyde.Thus, linalool is converted to citral in high yield.
- Carlsen, Per H.J.,Braenden, Jon Eric
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p. 313 - 317
(2007/10/02)
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- DIRECT MEASUREMENT OF THE RATES OF REKETONIZATION OF DIENOLATES PRODUCED BY PHOTOCHEMICAL ENOLIZATION OF Β-ALKYL Α,Β-UNSATURATED KETONES IN AQUEOUS BASIC SOLUTION
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The transient dienols produced by irradiation of five α,β-unsaturated ketones possessing γ-hydrogen atoms were observed as the corresponding dienolates in aqueous basic solution by using the technique of flash photolysis.The transients reketonize by protonation of the dienolate at carbon or via a 1,5-hydrogen shift in the dienol.The rates of both processes were measured; protonation by water at carbon of the dienolates occurs at room temperature at pseudo-first-order rates at ambient temperature in the range 375-1400 s-1, depending upon the structure of the dienolate.The temperature dependencies of these rates for two of the ketones were measured and indicate that the activation enthalpy, ΔH*, for the protonation step is ca. 50 kJ mol-1 and the activation entropy, ΔS*, is ca. -26 Jmol-1K-1.Reketonization of the dienols via the 1,5-shift mechanism occurs at room temperature at a rate in water of ca. 50 s-1 or slower, depending upon the structure of the dienol.The pKa for the dienol-dienolate equilibrium was measured for each ketone and was in the range 10.42-12.01 for the five systems examined.
- Duhaime, Randy M.,Weedon, Alan C.
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p. 2479 - 2483
(2007/10/02)
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- ETHYLIDYNE ALKYNES FROM ISOPROPYLIDENE OLEFINS
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A number of isopropylidene olefins was reacted with sodium nitrite in AcOH-H2O to give the corresponding ethylidyne alkynes with net loss of a CH4 unit.
- Abidi, S. L.
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p. 267 - 270
(2007/10/02)
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- Oxidation of Primary and Secondary Alcohols by the Catalysis of Palladium
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Saturated and unsaturated alcohols are oxidized to the corresponding ketones in good or excellent yields by using an aryl halide (phenyl bromide or mesityl bromide) as an oxidant and palladium(0) or -(II) as a catalyst (0.6-3 mol percent relative to the alcohol) in the presence of a base (NaH or K2CO3).The similar oxidation of primary alcohols provides the corresponding aldehydes and/or esters.The aldehyde/ester selectivity is correlated to the steric and electronic features of substrates.The procedure is applied to the oxidation of 1-primary,ω-primary diols to lactones.
- Tamaru, Yoshinao,Yamada, Yoshimi,Inoue, Kenji,Yamamoto, Youichi,Yoshida, Zen-ichi
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p. 1286 - 1292
(2007/10/02)
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- TOTAL SYNTHESIS OF p-MENTHENOLIDES
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A general approach to both cis- and trans-fused α-methylene γ-butyrolactones has been developed.This includes a new, mild method for the oxidation of α,β-unsaturated aldehydes.In addition, a new method to couple trans-α-methylene hydroxy acids into trans-lactones or, alternatively, cis-lactones has been developed.This strategy has been applied to the total synthesis of both cis- and trans-p-menthenolide, prepared in 35percent (trans) and 21percent (cis) overall yields from isopulegol.
- Bal, Balkrishna S.,Pinnick, Harold W.
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p. 2091 - 2104
(2007/10/02)
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- α-Isopropenylation of Ketones. Use of an Enol Ether-Iron Complex as an Isopropenyl Cation Equivalent
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The complex C5H5Fe(CO)2(ethyl isopropenyl ether)+BF4- functions as an isopropenyl cation equivalent in the isopropenylation of cyclohexanone enolates.
- Chang, Tony C. T.,Rosenblum, Myron
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p. 4103 - 4105
(2007/10/02)
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