- 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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- Continuous flow synthesis of menthol: Via tandem cyclisation-hydrogenation of citronellal catalysed by scrap catalytic converters
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A continuous flow synthesis of menthol starting from citronellal catalysed by scrap catalytic converters is reported. The reaction was conducted in a tandem system connecting in series two catalytic systems, with the first having Lewis acid properties (favouring the cyclisation of citronellal to isopulegols) and the second having hydrogenation catalytic activity (catalysing the hydrogenation of isopulegols to menthols). A Lewis acid catalyst was prepared by supporting iron oxide nanoparticles over a waste material, i.e. the ceramic core of scrap catalytic converters (SCATs) via a microwave assisted method. Most importantly, SCATs, containing a low residual noble metal content, could be directly employed in the second step as hydrogenation catalysts. The reaction was performed studying the influence on the yield and selectivity to (-)-menthol of various reaction parameters (T, p and flow rate). Under the best reaction conditions (at a flow rate of 0.1 mL min-1 and at 373 K and 413 K for cyclisation and hydrogenation steps respectively) a conversion of >99% of (+)-citronellal to (-)-menthol with 77% final yield was achieved.
- Zuliani, Alessio,Cova, Camilla Maria,Manno, Roberta,Sebastian, Victor,Romero, Antonio A.,Luque, Rafael
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p. 379 - 387
(2020/02/13)
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- A synthetic process of L-menthol
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The invention relates to the field of spice synthesis and particularly relates to a synthetic process of L-menthol. The process includes steps of d,l-menthol synthesizing, d,l-menthol rectification, d,l-menthol esterification, d,l-menthyl benzoate rectification, d,l-menthyl benzoate resolution, D-menthol synthesizing, menthol isomerization and L-menthol synthesizing. The process adopts thymol that is a simple, easily available and cheap chemical product as a raw material. Esterification conditions are optimized and the esterification and rectification are performed at the same time so as to allow the esterification to be converted into a way beneficial to d,l-menthyl benzoate production, thus increasing the esterification yield. Crystallization and resolution are optimized by utilization of the d,l-menthyl benzoate. Preparation of the L-menthol by the process is characterized by being high in yield, low in cost, simple and convenient in operation, suitable for continuous and large-scale production, and the like. According to the process, operation of the process is cyclic with a whole system being sealed, and the process is free of waste water, energy-saving and environmental friendly.
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Paragraph 0076; 0077; 0078
(2017/02/24)
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- Facile Protocol for Catalytic Frustrated Lewis Pair Hydrogenation and Reductive Deoxygenation of Ketones and Aldehydes
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A series of ketones and aldehydes are reduced in toluene under H2 in the presence of 5 mol % B(C6F5)3 and either cyclodextrin or molecular sieves affording a facile metal-free protocol for reduction to alcohols. Similar treatment of aryl ketones resulted in metal-free deoxygenation yielding aromatic hydrocarbons.
- Mahdi, Tayseer,Stephan, Douglas W.
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supporting information
p. 8511 - 8514
(2015/11/27)
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- P450-catalyzed regio- and stereoselective oxidative hydroxylation of disubstituted cyclohexanes: Creation of three centers of chirality in a single CH-activation event This paper is dedicated to the memory of Harry H. Wasserman
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Wild-type P450-BM3 is able to catalyze in a highly regio- and diastereoselective manner the oxidative hydroxylation of non-activated disubstituted cyclohexane derivatives lacking any functional groups, including cis- and trans-1,2-dimethylcyclohexane, cis- and trans-1,4-dimethylcyclohexane, and trans-1,4-methylisopropylcyclohexane. In all cases except chiral trans-1,2-dimethylcyclohexane as substrate, the single hydroxylation event at a methylene group induces desymmetrization with simultaneous creation of three centers of chirality. Certain mutants increase selectivity, setting the stage for future directed evolution work.
- Ilie, Adriana,Agudo, Rubén,Roiban, Gheorghe-Doru,Reetz, Manfred T.
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p. 470 - 475
(2015/02/02)
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- PROCESS FOR THE PREPARATION OF MENTHOL
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The invention relates to a process for the preparation of 2-isopropyl-5-methylcyclohexanol (D,L-menthol) via the hydrogenation of thymol to menthone and subsequent further hydrogenation to give D,L-menthol.
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Paragraph 0085-0086
(2014/03/25)
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- PROCESS FOR THE PREPARATION OF MENTHOL
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The invention relates to a process for the preparation of 2-isopropyl-5-methylcyclohexanol (menthol) via the hydrogenation of thymol to neomenthol and the subsequent isomerization to give D/L (+/?)-menthol.
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Paragraph 0049-0053
(2014/03/25)
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- Highly practical iron-catalyzed C-O cleavage reactions
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Facile iron-catalyzed cleavage of various allyl, cinnamyl and benzyl C-O linkages has been effected in the presence of ethylmagnesium chloride. The protocol is operationally simple (xylene-THF, r.t., 1 h), requires low catalyst loading (1 mol% FeCl2) and tolerates halides, esters, amines, ethers and olefins. The allyl moiety is converted to volatile hydrocarbons which renders laborious product separation unnecessary.
- Gaertner, Dominik,Konnerth, Hannelore,Von Wangelin, Axel Jacobi
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p. 2541 - 2545
(2013/09/24)
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- MOFs as multifunctional catalysts: One-pot synthesis of menthol from citronellal over a bifunctional MIL-101 catalyst
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A bifunctional MOF catalyst containing coordinatively unsaturated Cr 3+ sites and palladium nanoparticles (Pd@MIL-101) has been used for the cyclization of citronellal to isopulegol and for the one-pot tandem isomerization/hydrogenation of citronellal to menthol. The MOF was found to be stable under the reaction conditions used, and the results obtained indicate that the performance of this bifunctional solid catalyst is comparable with other state-of-the-art materials for the tandem reaction: Full citronellal conversion was attained over Pd@MIL-101 in 18 h, with 86% selectivity to menthols and a diastereoselectivity of 81% to the desired (-)-menthol, while up to 30 h were necessary for attaining similar values over Ir/H-beta under analogous reaction conditions. The Royal Society of Chemistry 2012.
- Cirujano,Llabres I Xamena,Corma
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scheme or table
p. 4249 - 4254
(2012/05/07)
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- One-pot synthesis of menthol catalyzed by a highly diastereoselective Au/MgF2 catalyst
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No toxic compounds such as KCN and no thermal activation is required for the preparation of Au/MgF2 complexes by a simple and facile incipient wetness impregnation method in which hydrogen tetrachloroaurate (HAuCl 4) is the gold precursor. One of the complexes prepared exhibits unique catalytic properties and serves as a heterogeneous catalyst for the highly diastereoselective one-pot synthesis of (±)-menthol from citronellal (see picture).
- Negoi, Alina,Wuttke, Stefan,Kemnitz, Erhard,MacOvei, Dan,Parvulescu, Vasile I.,Teodorescu,Coman, Simona M.
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supporting information; experimental part
p. 8134 - 8138
(2011/02/24)
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- One-step microwave-assisted asymmetric cyclisation/hydrogenation of citronellal to menthols using supported nanoparticles on mesoporous materials
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The selective conversion of citronellal to menthols, with good diastereoselectivities to (-)-menthol for the case of (+)-citronellal as starting material, can effectively be carried out in a one-step reaction under microwave irradiation catalysed by supported nanoparticles on mesoporous materials. 2% Pt/Ga-MCM-41 was found to be the optimum catalyst for the reaction, with a quantitative conversion of starting material and selectivities above 85% to menthols obtained in short reaction times (typically 15 min). These results constitute the first report of a simple microwave-assisted one-step cyclisation/hydrogenation process for the production of menthols.
- Balu, Alina Mariana,Campelo, Juan Manuel,Luque, Rafael,Romero, Antonio Angel
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experimental part
p. 2845 - 2849
(2010/08/21)
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- Hydrogen-transfer reduction of carbonyl compounds promoted by nickel nanoparticles
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Nickel(0) nanoparticles, generated from nickel(II) chloride, lithium powder and a catalytic amount of 4,4-di-tert-butylbiphenyl (DTBB) in THF at room temperature, have been found to promote the reduction of a variety of ketones and aldehydes by transfer hydrogenation using isopropanol as the hydrogen donor. The nickel nanoparticles were characterised and could be re-utilised with a good performance in the absence of a base. A mechanistic study demonstrates that the reaction proceeds through a dihydride-type mechanism.
- Alonso, Francisco,Riente, Paola,Yus, Miguel
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p. 1847 - 1852
(2008/09/18)
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- Design of catalyst systems for the one-pot synthesis of menthols from citral
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Stable, active, and highly selective bifunctional Ni/Al-MCM-41 catalysts were developed for the one-pot synthesis of menthols from citral. The liquid-phase hydrogenation of citral to citronellal was studied on silica-supported noble (Pt, Pd, Ir) and nonnoble (Ni, Co, Cu) metals. It was found that citronellal is selectively formed at the beginning of the reaction only on Pd and Ni catalysts. The consecutive ene-cyclization of citronellal to isopulegols was investigated on solid acids containing exclusively Lewis (ZnO/SiO2) or strong Broensted (CsHPA) acid sites, and also on catalysts containing both Lewis and Broensted acid sites of either strong (zeolites, SiO2-Al2O3) or moderate (Al-MCM-41) strength. The isopulegol formation rate was higher on samples exhibiting dual Lewis/Broensted acidity, such as SiO2-Al2O3, Al-MCM-41, and zeolite HBEA. Based on these previous results, bifunctional catalysts containing Pd or Ni supported on SiO2-Al2O3, Al-MCM-41, or zeolite HBEA were prepared and tested for citral conversion to menthols. The catalyst stability and the effect of hydrogen pressure and metal loading on menthol productivity were also investigated. The best catalyst was Ni(8%)/Al-MCM-41, which yielded more than 90% menthols at 2026.0 kPa and showed no significant deactivation after two consecutive catalytic tests.
- Trasarti,Marchi,Apesteguia
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p. 155 - 165
(2008/02/03)
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- Carbonyl reduction with CaH2 and R3SiCl catalyzed by ZnCl2
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Ketones and aldehydes were effectively reduced to the corresponding alcohols (or their silyl ethers) by the reaction with CaH2 and R3SiCl in the presence of a catalytic amount of ZnCl2. In the absence of the carbonyl substrate, the reagent reduced R3SiCl to the corresponding hydrosilane under mild reaction conditions.
- Tsuhako, Akiko,He, Jing-Qian,Mihara, Mariko,Saino, Naoko,Okamoto, Sentaro
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p. 9120 - 9123
(2008/09/17)
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- Domino-cyclisation and hydrogenation of citronellal to menthol over bifunctional Ni/Zr-Beta and Zr-beta/Ni-MCM-41 catalysts
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The one-pot conversion of (±)-citronellal to menthol can be selectively catalysed by either a bifunctional Ni/Zr-zeolite beta catalyst or a dual catalyst system of Zr-beta and Ni/MCM-41, giving a high diastereoselectivity to (±)-menthol of 90-94%. The Royal Society of Chemistry 2006.
- Nie, Yuntong,Chuah, Gaik-Khuan,Jaenicke, Stephan
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p. 790 - 792
(2008/02/03)
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- METHOD FOR PRODUCING MENTHOL
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To the invention relates to a method for producing menthol by catalytically hydrogenating compounds, which comprise the carbon skeleton of methane having at least one double bond and which are substituted at the 3-position by oxygen, and/or by catalytically rearranging stereoisomers of methanol in the presence of hydrogen and doped nickel catalysts.
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Page/Page column 8-10
(2008/06/13)
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- Chiral aminoalcohols with a menthane skeleton as catalysts for the enantioselective addition of diethylzinc to benzaldehyde
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Novel chiral aminoalcohols were synthesized by highly diastereoselective addition of Me3SiCN and LiCH2CN to (-)-menthone followed by LiAlH4 reduction. The addition of CH2=CH-MgBr and PhCH=CH-MgBr to menthone and the following epoxidation, provided useful hydroxy epoxides, one of which could be aminolyzed to afford an aminodiol. In one case, the configuration of the newly formed epoxidic stereogenic center was determined by X-ray crystallography. When applied as catalysts in the enantioselective addition of Et2Zn to benzaldehyde, the aminoalcohols induced enantiomeric excesses (e.e.s) of up to 77%.
- Panev, Stefan,Linden, Anthony,Dimitrov, Vladimir
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p. 1313 - 1321
(2007/10/03)
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- Highly regio- and stereoselective reductions of carbonyl compounds in aqueous glycosidic media
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Highly regioselective reductions of α,β-unsaturated ketones to the corresponding allylic alcohols were performed in essentially quantitative yields in aqueous media containing either glycosidic surfactants or amphiphilic carbohydrates. Reductions of cyclohexanones and cyclohexenones lead under the same conditions, stereoselectively to reduced compounds bearing an equatorial alcohol function. Hydrophobic interactions between amphiphilic carbohydrates and lipophilic substrates were modelized and should account for the observed stereodifferentiation.
- Denis, Cecile,Laignel, Benoit,Plusquellec, Daniel,Le Marouille, Jean-Yves,Botrel, Alain
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- ENZYMATIC RECOGNITION OF DIASTEREOMERIC ESTERS
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Aiming to improve the enantioselectivity of enzymatic resolution of esters, lipase catalyzed hydrolysis of (D)- and (L)-2-chloropropanoates of four racemic alcohols and transesterification of ethyl (DL)-2-chloropropanoate with optically pure alcohols was investigated.Thus, (rac)-endo-2-norbornyl (L)-2-chloropropanoate was hydrolized by lipase P about 5 times more selectively than its corresponding (D)-counterpart and optically pure (1R,2S,5R)-menthol was obtained by transesterification of its racemate with ethyl (D)-2-chloropropanoate using Candida cylindracea (CC)lipase.From the results obtained it seems obvious that lipases CC and P mainly can recognize the chirality of an alcohol moiety rather than that of an acid
- Rabiller, C. G.,Koenigsberger, .,Faber, K.,Griengl, H.
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p. 4231 - 4240
(2007/10/02)
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- STEREOSELECTIVE HYDROGENATION OF A MENTHONE-ISOMENTHONE MIXTURE ON HETEROGENEOUS NICKEL, NICKEL-COBALT, AND COBALT CATALYSTS
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A study was carried out on the effect of the nature of the catalysts, additives, and solvents on the stereoselectivity of the liquid-phase hydrogenation of an equilibrium menthone-isomenthone mixture to give menthols.Neoisomenthol, which is the least stable of all the menthol isomers, was predominantly formed on a cobalt catalyst modified by (+)-tartaric acid in ethyl acetate at 130 deg C and 10 MPa.
- Zubareva, N. D.,Klabunovskii, E. I.,Kheifits, L. A.
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p. 1765 - 1768
(2007/10/02)
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- STEREOCHEMICAL EVIDENCE FOR SINGLE ELECTRON TRANSFER MECHANISM IN THE REDUCTION OF CYCLIC KETONES WITH ALKOXYALUMINIUM DICHLORIDES
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The stereochemical results of the reduction of cyclic ketones with alkoxyaluminium dichlorides do not conform to the conventional polar cyclic mechanism and may be explained by a single electron transfer mechanism.
- Nasipuri, Dhanonjoy,Gupta, Mita Datta,Banerjee, Satinath
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p. 5551 - 5554
(2007/10/02)
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- Enzymic Resolution of (+/-)-axial-Alcohols via Asymmetric Hydrolysis of Corresponding Chloroacetates by Microorganisms
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Asymmetric hydrolysis of chloroacetates of (+/-)-axial-alcohols (+/-)-neomenthol (2), (1RS,4aRS,8aSR)-decahydro-1-naphthol (6) by Trichoderma koningi gave (-)-(1S,3R,4R)-neomenthol (2) (54percent optical purity, o.p.) and (-)-(1R,4aR,8aS)-decahydro-1-naphthol (6) (66percent o.p.) with their enantiomeric chloroacetates.However, the chloroacetate of (2RS,4aRS,8aSR)-decahydro-2-naphthol (10) was hydrolyzed by T. koningi to give the (-)-alcohol (10) (12percent o.p.) with low enantioselectivity.
- Oritani, Takayuki,Ichimura, Michio,Hanyu, Yoshifumi,Yamashita, Kyohei
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p. 2613 - 2618
(2007/10/02)
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- Novel chiral ethers and their use in resolution of alcohols and phenols
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Novel ethers of organic compounds containing chiral atoms of the formula STR1 wherein A is a hydrocarbonated chain of 1 to 10 groups, the said chain containing one or more heteroatoms, one or more unsaturations, the assembly of the groups constituting the chain may represent a mono- or polycyclic system, including a system of the spiro or endo type, the chain A can contain one or more chiral atoms or the lactone moiety can present a chirality due to the dissymetric spatial configuration of the whole of the molecule and Z is selected from the group consisting of primary, secondary or tertiary alcohol moiety containing at least an asymetric carbon atom, a phenol moiety substituted comprising at least one asymetric carbon atom and an substituted alcohol or phenol moiety with a chirality due to the dissymetric spatial configuration of the whole of the molecule, with the proviso Z is not (R) or (S) α-cyano-3-phenoxy-benzyl when A is STR2 which are useful for the resolution of compounds of the formulae STR3 wherein A and Z have the above definitions and X is selected from the group consisting of hydrogen and alkyl of 1 to 4 carbon atoms.
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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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