- Effective, selective hydroalkoxylation/cyclization of alkynyl and allenyl alcohols mediated by lanthanide catalysts
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Catalytic hydroalkoxylation/cyclization reactions of alkynyl and allenyl alcohols are efficiently mediated by homoleptic lanthanide amides Ln[N(SiMe3)2]3 (Ln = La, Nd, Sm, Y, and Lu). Conversions are found to be highly selective with products distinctly different from those produced by conventional transition metal catalysts. Turnover frequencies as high as 18.0 h-1 at 60 °C are observed. Kinetic studies indicate that these transformations are zero-order in [substrate] and first-order in [catalyst]. Catalytic cycles are proposed in which insertion of C-C unsaturation into a Ln-O bond is turnover-limiting. Copyright
- Yu, Xianghua,Seo, SungYong,Marks, Tobin J.
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- Formation and atmospheric reactions of 4,5-dihydro-2-methylfuran
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In the troposphere, the dominant loss process for alkanes is by reaction with the hydroxyl (OH) radical. 4,5-Dihydro-2-methylfuran (DHMF) can be formed from cyclization of 5-hydroxy-2-pentanone, an important gas-phase photooxidation product of n-pentane and a representative 1,4-hydroxycarbonyl. Rate constants and products of the gas-phase reactions of DHMF with OH radicals, NO3 radicals, and ozone in situ FTIR were determined at 298 K and 1 atm. Photolysis of DHMF in dry air showed ～ 1% loss of DHMF after 30 min irradiation, indicating that photolysis of DHMF during the OH radical reactions was negligible (-4/min. The presence of water vapor DHMF decayed to form 5-hydroxy-2-pentanone with a measured lifetime at 5% relative humidity of 3.5 hr. The set of prominent bands at 1769, 1236, and 1057/cm indicated the presence of an ester as a major product.
- Martin, Pilar,Tuazon, Ernesto C.,Aschmann, Sara M.,Arey, Janet,Atkinson, Roger
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- REACTION OF 2-METHYL-4,5-DIHYDROFURAN WITH HYDROGEN CHLORIDE
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Reaction of 2-methyl-4,5-dihydrofuran with HCl at 0 deg C yields 5'-chloro-2'-pentanone (13percent) and 1'-(2-methyltetrahydrofuryl-2)-5'-chloro-2'-pentanone (27percent) and at 200 deg 5'-chloro-2'-pentanone exclusively. Keywords: 2-methyl-4,5-dihydrofuran, 5'-chloro-2'-pentanone, 1'-(2-methyltetrahydrofuryl-2)-5'-chloro-2'-pentanone.
- Polivin, Yu. N.,Karakhanov, R. A.,Sheveleva, T. S.,Ugrak, B. I.,Kelarev, V. I.
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- Direct Observation of Acyl Anion Equivalents by Carbon-13 Fourier Transform Nuclear Magnetic Resonance
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The vinyl anions derived from 2,3-dihydrofuran, 2,3-dihydro-4H-pyran, and ethoxyethene have been examined by carbon-13 FT NMR.The vinyl C-H coupling constants (1J13C-1H) have been measured for the ethers and the anions.Observation of vinyl anions derived from vinyl ethers is readily accomplished with carbon-13 NMR.While all carbon resonances are shifted upon formation of the anion the most obvious effect is the large (56-61 ppm) downfield shift of the vinyl carbon bonded to lithium.In no case was allylic deprotonation observed under the reactions conditions.
- Oakes, Fred T.,Sebastian, John F.
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- Preparation method of 4-(BOC-amino)-1-butanol
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The invention discloses a preparation method of 4-(BOC-amino)-1-butanol. The method comprises the following steps: reacting a proper amount of 2, 3-dihydrofuran with an acidic solution to obtain 2, 3-dihydro-5-methyl furan; mixing the obtained 2, 3-dihydro-5-methyl furan with hydrochloride, and then adding the mixture into an alkaline solution for reaction to obtain isobutyl nitrite; reacting isobutyl nitrite under the action of a reducing agent to generate 4-amino-1-butyl alcohol; and reacting 4-amino-1-butyl alcohol with di-tert-butyl dicarbonate in tetrahydrofuran to generate 4-(BOC-amino)-1-butyl alcohol; according to the preparation method of the 4-(BOC-amino)-1-butanol, the total yield of the product is as high as 70%, the reaction temperature is low, and the safety coefficient is high), the reducing agent is cheaper than that in the prior art, the experimental operation method is simple, the steps are short, and the method is suitable for large-scale production.
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Paragraph 0051-0052; 0058-0059; 0065-0066
(2021/01/28)
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- S-Block cooperative catalysis: Alkali metal magnesiate-catalysed cyclisation of alkynols
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Mixed s-block metal organometallic reagents have been successfully utilised in the catalytic intramolecular hydroalkoxylation of alkynols. This success has been attributed to the unique manner in which these reagents can overcome the challenges of the reaction: namely OH activation and coordination to and then addition across a CC bond. In order to optimise the reaction conditions and to garner vital catalytic system requirements, a series of alkali metal magnesiates were enlisted for the catalytic intramolecular hydroalkoxylation of 4-pentynol. In a prelude to the main investigation, the homometallic magnesium dialkyl reagent MgR2 (where R = CH2SiMe3) was utilised. This reagent was unsuccessful in cyclising the alcohol into 2-methylenetetrahydrofuran 2a or 5-methyl-2,3-dihydrofuran 2b, even in the presence of multidentate Lewis donor molecules such as N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA). Alkali metal magnesiates MIMgR3 (when MI = Li, Na or K) performed the cyclisation unsatisfactorily both in the absence/presence of N,N,N′,N′-tetramethylethylenediamine (TMEDA) or PMDETA. When higher-order magnesiates (i.e., MI2MgR4) were employed, in general a marked increase in yield was observed for MI = Na or K; however, the reactions were still sluggish with long reaction times (22-36 h). A major improvement in the catalytic activity of the magnesiates was observed when the crown ether molecule 15-crown-5 was combined with sodium magnesiate Na2MgR4(TMEDA)2 furnishing yields of 87% with 2a:2b ratios of 95:5 after 5 h. Similar high yields of 88% with 2a:2b ratios of 90:10 after 3 h were obtained combining 18-crown-6 with potassium magnesiate K2MgR4(PMDETA)2. Having optimised these systems, substrate scope was examined to probe the range and robustness of 18-crown-6/K2MgR4(PMDETA)2 as a catalyst. A wide series of alkynols, including terminal and internal alkynes which contain a variety of potentially reactive functional groups, were cyclised. In comparison to previously reported monometallic systems, bimetallic 18-crown-6/K2MgR4(PMDETA)2 displays enhanced reactivity towards internal alkynol-cyclisation. Kinetic studies revealed an inhibition effect of substrate on the catalysts via adduct formation and requiring dissociation prior to the rate limiting cyclisation step.
- Fairley, Michael,Davin, Laia,Hernán-Gómez, Alberto,García-álvarez, Joaquín,O'Hara, Charles T.,Hevia, Eva
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p. 5821 - 5831
(2019/06/18)
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- Preparation method and application of 2-methyl tetrahydrofuran-3-thiol
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The invention discloses a preparation method of 2-methyl tetrahydrofuran-3-thiol. According to the preparation method, 5-hydroxy-2-pentanone is used as a raw material, and the 2-methyl tetrahydrofuran-3-thiol is prepared by carrying out a dispersion reaction. The preparation method has the advantages that when the 5-hydroxy-2-pentanone (I) and phosphoric acid are taken as raw materials for preparing 4,5-dihydro-2-methylfuran (II), less isomer is produced, so that the generation of by-products in a reaction process can be effectively reduced, and the product quality is greatly improved; an intermediate 2-methyltetrahydrofuran-3-thiol acetate (III) is obtained by enabling the 4,5-dihydro-2-methylfuran (II) to react with thioacetic acid, and 2-methyltetrahydrofuran-3-thiol is then prepared, so that the preparation route is short in reaction time.
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Paragraph 0018; 0040-0045
(2018/09/12)
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- Pharmaceutical intermediate 5-chloro-2-pentanone synthesis method
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The invention discloses a pharmaceutical intermediate 5-chloro-2-pentanone synthesis method, which comprises: placing 2-methylfuran in a reaction kettle, introducing nitrogen gas, adding a Cu-Mn-Mo composite oxide, controlling the temperature at 20-30 DEG C, introducing hydrogen, controlling the pressure at 0.25-0.3 MPa, carrying out a reaction for 30-45 min, stopping the reaction, filtering the prepared mixture, collecting the filtrate, and preparing 2-methyl-4,5-dihydrofuran; and mixing the prepared 2-methyl-4,5-dihydrofuran and diethyl ether, adding the mixture to a reaction kettle, controlling the temperature at 70-80 DEG C, adding FeCl3, uniformly stirring, controlling the pressure at 0.05-0.08 Mpa, carrying out microwave treatment for 30-45 min, carrying out a stirring reflux reaction for 2-3 h, adding water after completing the reaction, uniformly mixing, carrying out a stirring reaction for 1-2 h, restoring to a room pressure and a room temperature, collecting the organic layer, and carrying out pressure reducing distillation to prepare 5-chloro-2-pentanone. According to the present invention, the synthesis method has characteristics of simple operation, mild condition, less by-product, high product purity and high product yield.
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Paragraph 0022; 0031; 0040; 0046; 0049; 0058
(2018/10/11)
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- Preparing method of cyclopropyl methyl ketone
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The invention provides a preparing method of cyclopropyl methyl ketone. The method includes the steps that 2-methyl furan generates a hydrogenation under the condition that a hydrogenation catalyst and hydrogen exist to prepare 2-methyl-4,5-dihydrofuran, and after a hydrogenation catalyst in a reaction mass is removed, the 2-methyl-4,5-dihydrofuran is subject to a isomerization reaction under the condition that an isomerization catalyst exists and the temperature ranges from 10 DEG C to 100 DEG C to obtain the cyclopropyl methyl ketone. According to the preparing method, the production period of a product is short, reactions are free of process waste water, the catalysts can be recycled and reused, and the preparing method is particularly suitable for replacing the process that the cyclopropyl methyl ketone is generated through the 2-methyl furan after multi-step reactions.
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Paragraph 0009; 0030
(2017/08/28)
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- The mechanism of gold(I)-catalyzed hydroalkoxylation of alkynes: An extensive experimental study
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An extensive experimental study of the mechanism of gold(I)-catalyzed hydroalkoxylation of internal alkynes has been conducted by using NMR spectroscopy. This study was focused on the organogold intermediates, observations of actual catalytic intermediates in situ, and the reaction kinetics that are involved in this reaction. Based on the experimental results, a complete mechanistic picture was established, including on- and off-cycle processes that explain the role of diaurated species. We have shown that gold-catalyzed hydroalkoxylation of internal alkynes is a reaction that requires only one gold atom for the catalytic cycle, disproving a recent hypothesis regarding the involvement of cooperative gold catalysis.
- Zhdanko, Alexander,Maier, Martin E.
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supporting information
p. 1918 - 1930
(2014/03/21)
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- Quantitative evaluation of the stability of gem -diaurated species in reactions with nucleophiles
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The reactivity of diaurated species toward nucleophiles was investigated. The reaction yields vinyl gold species and is described as simple SN2 ligand exchange at gold. Using suitably strong nucleophiles, equilibrium constants were determined to measure the stability of various diaurated species. On the basis of these equilibrium constants the influence of ligand and the nature of vinyl cores on the stability were analyzed. These results have direct implication for gold catalysis: it was demonstrated that vinyl gold intermediates bind the catalytic LAu+ species generally stronger than an alkyne (the substrate) by a factor of 106-109. This demonstrates that the formation of diaurated species from vinyl gold intermediates is thermodynamically favored in a catalytic reaction.
- Zhdanko, Alexander,Maier, Martin E.
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supporting information
p. 2000 - 2006
(2013/05/08)
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- Synthesis of gem-diaurated species from alkynols
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A number of enol ether-derived diaurated species were synthesized directly from different alkynols and cationic gold complexes in the presence of a non-nucleophilic base (proton sponge). The reaction can be easily applied for in situ generation of diaurated species from all common types of hydroalkoxylation substrates: 5-endo, 5-exo/6-endo, 6-exo/7-endo and intermolecular types. Six examples were also synthesized in individual state as stable hexafluoroantimonate salts. Whereas diaurated species are obtained reliably from all conventional mononuclear gold catalysts, application of binuclear ones often gave diaurated species with unusual properties. The preliminary results point to complexities of behavior of binuclear gold catalysts and would require more research in future for this subclass. The formation of diaurated species from various gold-oxo compounds (LAu)2OH+, (LAu) 3O+, and LAuOH (L=phosphine ligand) was also studied. Of these three types, only (LAu)2OH+ is reactive, whereas (LAu)3O+ and LAuOH are not reactive alone but require acidic promoters to enable the reaction. These differences in reactivity were explained by ability of these compounds to generate the necessary acetylene π-complex intermediate. Catch the gold fish: A number of enol ether derived diaurated species were synthesized directly from different alkynols and cationic gold complexes in the presence of a non-nucleophilic base (proton sponge; see scheme). The reaction can be easily applied for the in situ generation of diaurated species from all common types of hydroalkoxylation substrates: 5-endo, 5-exo/6-endo, 6-exo/7-endo and even intermolecular types. The reactivity of various gold oxo compounds (LAu)2OH+, (LAu) 3O+, and LAuOH (L=phosphine ligand) towards alkynols was also examined. Copyright
- Zhdanko, Alexander,Maier, Martin E.
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supporting information
p. 3932 - 3942
(2013/04/24)
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- Alkaline earth catalysis of alkynyl alcohol hydroalkoxylation/cyclization
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Heavier alkaline earth bis(trimethylsilyl)amides [Ae{N(SiMe 3)2}2]2 (Ae = Ca, Sr, Ba) are shown to act as effective precatalysts for the regioselective intramolecular hydroalkoxylation/cyclization of a wide range of alkynyl and allenyl alcohols. In the majority of cases, cyclization of alkynyl alcohols produces mixtures of the possible endo- and exocyclic enol ether products, rationalized as a consequence of alkynylalkoxide isomerization to the corresponding allene derivatives. Cyclization rates for terminal alkynyl alcohols were found to be significantly higher than for substrates bearing internal alkynyl substituents, while the efficacy of cyclization was in general found to be determined by a combination of stereoelectronic influences and the thermochemical viability of the specific alkaline earth metal catalysis, which we suggest is determined by the individual M-O bond strengths. Kinetic studies have provided a rate law pertaining to a pronounced catalyst inhibition with increasing [substrate], indicating that turnover-limiting insertion of C-C unsaturation into the M-O bond requires the dissociation of substrate molecules away from the Lewis acidic alkaline earth center.
- Brinkmann, Christine,Barrett, Anthony G. M.,Reid, Stephanie,Hill, Michael S.,Procopiou, Panayiotis A.
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p. 7287 - 7297,11
(2020/09/02)
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- Oxidant-free lactonization of diols using a hydrotalcite-supported copper catalyst
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We newly synthesized well-crystallized hydrotalcite-supported copper nanoparticles, denoted as Cu/HT(c), which acted as a highly efficient heterogeneous catalyst for oxidant-free lactonization of various diols under liquid-phase conditions. The Cu/HT(c) catalyst could be recovered by simple filtration and reused without the significant loss of its activity and selectivity.
- Mikami, Yusuke,Ebata, Kaori,Mitsudome, Takato,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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experimental part
p. 855 - 861
(2010/09/16)
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- Determination of the isomerization rate constant HOCH2CH2CH2CH(OO·)CH3→HOC·HCH2 CH2CH(OOH)CH3. Importance of intramolecular hydroperoxy isomerization in tropospheric chemistry
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The rate constant of the title reaction is determined during thermal decomposition of di-n-pentyl peroxide C5H11O-OC5H11 in oxygen over the temperature range 463-523 K. The pyrolysis of di-n-pentyl peroxide in O2/N2 mixtures is studied at atmospheric pressure in passivated quartz vessels. The reaction products are sampled through a micro-probe, collected on a liquid-nitrogen trap and solubilized in liquid acetonitrile. Analysis of the main compound, peroxide C5H10O3, was carried out by GC/MS, GC/MS/MS [electron impact El and NH3 chemical ionization Cl conditions]. After micro-preparative GC separation of this peroxide, the structure of two cyclic isomers (3S*,6S*)3α-hydroxy-6-methyl-1,2-dioxane and (3R*,6S*)3α-hydroxy-6-methyl-1,2-dioxane was determined from 1H NMR spectra. The hydroperoxy-pentanal OHC-(CH2)2-CH(OOH)-CH3 is formed in the gas phase and is in equilibrium with these two cyclic epimers, which are predominant in the liquid phase at room temperature. This peroxide is produced by successive reactions of the n-pentoxy radical: a first one generates the CH3C·H(CH2)3OH radical which reacts with O2 to form CH3CH(OO·)(CH2)3OH; this hydroxy-peroxy radical isomerizes and forms the hydroperoxy HOC·H(CH2)2CH(OOH)CH3 radical. This last species leads to the pentanal-hydroperoxide (also called oxo-hydroperoxide, or carbonyl-hydroperoxide, or hydroperoxypentanal). By adding small amounts of NO (0-1.6×1015 molecules cm-3) to the di-n-pentyl peroxide/O2/N2 mixtures, the pentanal-hydroperoxide concentration was decreased, due to the consumption of RO2 radicals by reaction (7). The pentanal-hyroperoxide concentration was measured vs. NO concentration at ten temperatures (463-523 K). The isomerization rate constant involving the H atoms of the CH2-OH group was deduced. The comparison of this rate constant to thermokinetics estimations leads to the conclusion that the strain energy barrier of a seven-member ring transition state is low and near that of a six-member ring. Intramolecular hydroperoxy isomerization reactions produce carbonyl-hydroperoxides which (through atmospheric decomposition) increase concentration of radicals and consequently increase atmospheric pollution, especially tropospheric ozone, during summer anticyclonic periods. Therefore hydrocarbons used in summer should contain only short chains (4) hydrocarbons or totally branched hydrocarbons, for which isomerization reactions unlikely.
- Perrin,Heiss,Sahetchian,Kerhoas,Einhorn
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p. 875 - 887
(2007/10/03)
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- A Synthesis of 4-Oxo Carboxylic Acids, 4-Oxo Aldehydes, and 1,4-Diketones from γ-Lactones
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The α-methyldiphenylsilyl derivatives of γ-butyrolactone, γ-valerolactone, and the cis lactone of 2-hydroxycyclohexaneacetic acid have been reacted with Grignard reagents.The α-silylated lactones of γ-butyrolactone and γ-valerolactone react with a single equivalent of Grignard reagent to give a 2-substituted 4,5-dihydrofuran, which can be hydrolyzed and oxidized to 4-oxo carboxylic acids, 1,4-diketones, or 4-oxo aldehydes.The α-silylated fused lactone failed to react with ethylmagnesium bromide in refluxing tetrahydrofuran.An X-ray crystal structure of this silylated lactone indicated that this lack of reactivity is due to steric factors.
- Betancourt de Perez, Rosa M.,Fuentes, Lelia M.,Larson, Gerald L.,Barnes, Charles L.,Heeg, Mary Jane
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p. 2039 - 2043
(2007/10/02)
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- A FACILE SYNTHESIS OF 4-OXO CARBOXYLIC ACIDS FROM γ-BUTYROLACTONE
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An efficient, high-yield, three-step preparation of 4-oxo carboxylic acids from γ-butyrolactone via silylation and reaction with a Grignard reagent is presented.
- Fuentes, Lelia M.,Larson, Gerald L.
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p. 271 - 274
(2007/10/02)
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- The photolysis of tetrahydrofuran and of some of its methyl derivatives at 185 nm
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The uv photolysis of tetrahydrofuran, 1, 2-methyltetrahydrofuran, 2, cis-2,5-dimethylterahydrofuran, 3, trans-2,5-dimethyltetrahydrofuran, 4, and 2,2,5,5-tetramethyltetrahydrofuran, 5, has been investigated by product analysis in the liquid phase, and quantum yields have been determined.The photolysis of tetrahydrofuran itself was also studied in the gas phase at pressures ranging from 1 to 120 atm (pressurizing gas N2); and very little difference was found between the photolytic behaviour of the vapour at 120 atm and that of the liquid.The major products are in all cases the cyclopropanes and the corresponding carbonyl compounds, as well as the olefinic alcohols and the carbonyl compounds that are isomeric with the starting material.These products are considered to be formed by the two primary processes and . The cyclopropanes formed in reaction retain some excess energy (apparently more then is needed to realize the trimethylene form), and in the photolysis of tetrahydrofuran vaapour the hot cyclopropane rearranges to a considerable extent into propene.The propene to cyclopropane yield ratio falls strongly with increasing pressure, to a value of 0.065 at 120 atm.A similar value is observed in the liquid phase photolysis.The five-membered oxyl alkyl diradical from reaction is the likely intermediate in the cis-trans photoisomerization that is observable with the 2,5-dimethyltetrahydrofurans (Φ(cis -> trans) ca. Φ(trans -> cis) ca. 0.2).The photolysis of these compounds also demonstrates that steric factors have a strong bearing on the course of the reaction, e. g. the quantum yield of methylcyclopropane from the cis compound is 0.22, vs. 0.08 from the trans compound.Molecular hydrogen is produced if the tetrahydrofurans carry hydrogen in α-position.Its production is enhanced if the α-position is shared with a methyl group (1 gives a hydrogen quantum yield of 0.07, 2 of 0.17, 3 of 0.27, 4 of 0.29, and 5 of zero).
- Kizilkilic, Nuray,Schuchmann, Heinz-Peter,Sonntag, Clemens Von
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p. 2819 - 2826
(2007/10/02)
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