- BIS(BROMOMAGNESIO)TRIMETHYLSILYLMETHANE
-
The reaction of Me3SiCH(MgBr)2 with magnesium amalgam in diisopropyl ether furnished the di-Grignard reagent Me3SiCH(MgBr)2 in 70 percent yield.Derivatization with Me3SnCl gave Me3SiCH(SnMe3)2 (6,94percent).Witting type reaction occured readily with benzophenone (80percent), but the yield was low with cyclohexanone (13percent).
- Heisteeg, B. J. J. van de,Schat, G.,Tinga, M. A. G. M.,Akkerman, O. S.,Bickelhaupt, F.
-
-
Read Online
- Hydrogen-Catalyzed Acid Transformation for the Hydration of Alkenes and Epoxy Alkanes over Co-N Frustrated Lewis Pair Surfaces
-
Hydrogen (H2) is widely used as a reductant for many hydrogenation reactions; however, it has not been recognized as a catalyst for the acid transformation of active sites on solid surface. Here, we report the H2-promoted hydration of alkenes (such as styrenes and cyclic alkenes) and epoxy alkanes over single-atom Co-dispersed nitrogen-doped carbon (Co-NC) via a transformation mechanism of acid-base sites. Specifically, the specific catalytic activity and selectivity of Co-NC are superior to those of classical solid acids (acidic zeolites and resins) per micromole of acid, whereas the hydration catalysis does not take place under a nitrogen atmosphere. Detailed investigations indicate that H2 can be heterolyzed on the Co-N bond to form Hδ-Co-N-Hδ+ and then be converted into OHδ-Co-N-Hδ+ accompanied by H2 generation via a H2O-mediated path, which significantly reduces the activation energy for hydration reactions. This work not only provides a novel catalytic method for hydration reactions but also removes the conceptual barriers between hydrogenation and acid catalysis.
- Deng, Qiang,Deng, Shuguang,Gao, Ruijie,Li, Xiang,Tsang, Shik Chi Edman,Wang, Jun,Zeng, Zheling,Zou, Ji-Jun
-
p. 21294 - 21301
(2021/12/17)
-
- Reactivity of Lithium β-Ketocarboxylates: The Role of Lithium Salts
-
Lithium β-ketocarboxylates 1(COOLi), prepared by the reaction of lithium enolates 2(Li+) with carbon dioxide, readily undergo decarboxylative disproportionation in THF solution unless in the presence of lithium salts, in which case they are indefinitely stable at room temperature in inert atmosphere. The availability of stable THF solutions of lithium β-ketocarboxylates 1(COOLi) in the absence of carbon dioxide allowed reactions to take place with nitrogen bases and alkyl halides 3 to give α-alkyl ketones 1(R) after acidic hydrolysis. The sequence thus represents the use of carbon dioxide as a removable directing group for the selective monoalkylation of lithium enolates 2(Li+). The roles of lithium salts in preventing the disproportionation of lithium β-ketocarboxylates 1(COOLi) and in determining the course of the reaction with bases and alkyl halides 3 are discussed.
- Berton, Mateo,Mello, Rossella,Williard, Paul G.,González-Nú?ez, María Elena
-
supporting information
p. 17414 - 17420
(2017/12/15)
-
- Synthesis of sulphur-modified bifunctional hydrotalcites and study of their surface characteristics by inverse gas chromatography
-
In this study, various sulphur-modified hydrotalcite catalysts were prepared, and the influence of calcination temperature on their acid-base properties was investigated. Structural characterization of the catalysts was studied using X-ray powder diffraction, scanning electron microscopy, N2 physisorption, elemental analysis and Fourier transform infrared spectroscopy. The structural characterization indicated that the layer structure of all catalysts was retained but the specific surface areas were enlarged. Inverse gas chromatography was carried out to quantitatively determine the catalysts' acid-base properties by calculating the thermodynamic parameters, including dispersive surface free energy, adsorption free energy, adsorption enthalpy, and acid-base interaction constants. The results showed that the strength and content of acidic and alkaline sites were enhanced with increasing calcination temperature. Moreover, several typical aldol condensation reactions were selected to study the catalytic activity of the developed catalysts. The results showed that the sulphur-modified hydrotalcite catalysts possess high activity and good regenerability for typical aldol condensation reactions.
- Ren, Xiaoqian,Hu, Xi,Zhang, Feng,Wang, Junge,Liang, Jinhua,Wu, Wenliang,Jiang, Min,Wang, Jun
-
p. 4813 - 4820
(2015/10/05)
-
- Mass spectrometric studies of self-condensation products of cyclohexanone under alkaline conditions and synthesis of dodecahydrotriphenylene and triphenylene from easily available reactants
-
LC-MS was used to study products of cyclohexanone self-condensation under alkaline conditions. Improved methods (as compared to those described in the literature) for the preparation of dodecahydrotriphenylene and highly pure sublimed triphenylene were suggested based on the easily available and cheap reactants. Possible reasons of the low yield of the target dodecahydrotriphenylene in the step of oligomerization of cyclohexanone were identified.
- Kovalev,Kopchuk,Zyryanov,Khasanov,Rusinov,Chupakhin
-
p. 1539 - 1542
(2015/03/14)
-
- A selective solvent-free self-condensation of carbonyl compounds utilizing microwave irradiation
-
An environmentally benign microwave-assisted solvent-free self-condensation of carbonyl compounds was developed using catalytic amounts of triethylamine and lithium perchlorate. Changing the amount of lithium perchlorate helps in controlling the ratio of the single-condensation and double-condensation products. The effect of other additives and microwave activation was also investigated. The optimized conditions were then applied to various cyclic/acyclic ketones and aldehydes, with selectivity observed in many cases.
- Sharma, Lalit Kumar,Kim, Kyung Bo,Elliott, Gregory I.
-
supporting information; experimental part
p. 1546 - 1549
(2011/07/31)
-
- Thermodynamic properties for 2-(1′-hydroxycyclohexyl)cyclohexanone and equilibrium of dimerization of cyclohexanone
-
Thermodynamic properties of 2-(1′-hydroxycyclohexyl)cyclohexanone (ketol) are reported. The investigated compound is a byproduct from the caprolactam manufacture. The heat capacity of ketol was measured by vacuum adiabatic calorimetry (T = 5 K to T = 310 K) and by differential scanning calorimetry (T = 294 K to T = 370 K). The fusion temperature Tfus = 306.75 K and the mole fraction of the ketol sample (x = 0.9982) were found by fractional melting analysis. The molar enthalpy of fusion Δ fusHmo = (20.81 ± 0.02) kJ·mol-1 was determined in the adiabatic calorimeter. The standard molar thermodynamic functions of ketol in the condensed state were obtained with the use of these calorimetric measurements. The standard molar enthalpy of combustion of ketol ΔcHmo(cr, 298.15 K) = -(6963.0 ± 1.8) kJ·mol-1 was found by bomb calorimetry, and the standard molar enthalpy of formation Δ fHmo(cr, 298.15 K) = -(597.6 ± 2.4) kJ·mol-1 was derived. The equilibrium of dimerization of cyclohexanone with ketol formation was investigated in the temperature range 294 K to 367 K. The equilibrium constants (Ka) were obtained at five temperatures, and the enthalpy of the reaction at the average temperature ΔrHm(330.5 K) = -(34.4 ± 3.3) kJ·mol-1 was derived.
- Shevelyova, Marina P.,Kabo, Gennady J.,Blokhin, Andrey V.,Kabo, Audrey G.,Jursha, Joseph A.,Rajko, Anna A.
-
-
- Thermodynamics of 2-(1′-hydroxycyclohexyl)cyclohexanone: Vaporization, sublimation, and the ideal gas state thermodynamic properties
-
The thermodynamics of one of the byproducts of caprolactam production, 2-(1′-hydroxycyclohexyl)cyclohexanone (ketol), have been studied in this work. Saturated vapor pressure for liquid and crystalline ketol was measured by the Knudsen method in the temperature ranges from (308.2 to 330.4) K and from (289.6 to 300.8) K, respectively. Additionally, the saturated vapor pressures over ketol in the undercooled state and in the liquid were measured by the transpiration method in the temperature range from (287.9 to 303.0) K and from (308.0 to 351.5) K, respectively. The enthalpy of vaporization and the enthalpy of sublimation of ketol at the average temperatures studied were obtained indirectly from the temperature dependence of the vapor pressure measured by the Knudsen method as well as by the transpiration method. Furthermore, the standard molar enthalpy of sublimation was measured directly at 303.1 K using calorimetry. The entropy of ketol in the vapor state at (320.8 and 298.2) K was derived. The thermodynamic properties for 2-(1′-hydroxycyclohexyl) cyclohexanone in the ideal gas state were calculated from statistical mechanic calculations in the broad temperature range from (50 to 1000) K. The gaseous thermodynamic equilibrium constant K° (at 332.1 K) for cyclohexanone auto-condensation (side reaction of the caprolactam production) leading to 2-(1′-hydroxycyclohexyl)cyclohexanone was assessed.
- Shevelyova, Marina P.,Zaitsau, Dzmitry H.,Paulechka, Yauheni U.,Kabo, Gennady J.,Verevkin, Sergey P.
-
p. 1946 - 1952
(2007/10/03)
-
- The boron-mediated ketone-ketone aldol reaction
-
The first examples of the directed, boron-mediated aldol reaction between different ketones are presented. Transformation of a variety of ketones to their corresponding boron enolates with Chx2BCl/Et3N, followed by reaction with acceptor ketones in diethyl ether, and oxidation of the resultant boron aldolate (H2O2, MeOH/pH 7 buffer), provided the aldol addition products. The reaction was most facile when cyclic ketones were used, with the highest yields obtained for the reaction of boron enolates with cyclohexanone as the acceptor.
- Cergol, Katie M.,Turner, Peter,Coster, Mark J.
-
p. 1505 - 1509
(2007/10/03)
-
- Chemoselective aldol condensation in 5 mol dm 3 lithium perchlorate-nitromethane. A comparison with lithium perchloratediethyl ether medium
-
Aldol reactions of silyl enol ethers with aldehydes proceed in 5 mol dm 3 lithium perchlorate-nitromethane medium at ambient temperature. The reaction is highly chemoselective such that only aldehydes and cyclic ketones reacted while acyclic and aromatic ketones failed to react. The same reaction is not promoted in 5 mol dm"3 lithium perchlorate-diethyl ether medium. The difference between these two media is explained by the increased Lewis acidity of the lithium ion in nitromethane compared to that in ether.
- Sudha,Sankararaman
-
p. 383 - 386
(2007/10/03)
-
- Bis(amido)magnesium mediated aldol additions: First structural characterisation of an amidomagnesium aldolate intermediate
-
Bis(hexamethyldisilazido)magnesium has successfully been used to mediate aldol additions of selected ketones and aldehydes in hydrocarbon media, and the structure of an intermediate amido(aldolate), [{(Me3Si)2NMg[μ-OC(Me)-Bu(t)CHsub
- Allan, John F.,Henderson, Kenneth W.,Kennedy, Alan R.
-
p. 1325 - 1326
(2007/10/03)
-
- Highly controlled chemoselectivity of tin enolate by its hybridization state. Anionic complex of tin enolate coordinated by tetrabutylammonium bromide as halo selective reagent
-
The control of reactivity and/or selectivity of organotin(IV) enolates has been studied by means of a high coordination method in which the hybridization state of tin was effectively changed. An anionic tin complex, five-coordinated tin enolate 1(h), was formed by the coordination of bromide anion from tetrabutylammonium bromide (Bu4NBr) to neutral four-coordinated tin(IV) enolates 1(e). The highly coordinated enolates which attained a marked change in chemoselectivity have higher nucleophilicity to organic halides. In addition, they showed low nucleophilicity toward carbonyl moieties by the coordination of the bromide anion, whereas carbonyl addition readily proceeds using the usual four-coordinated tin enolate. NMR studies revealed the generation of HMPA- or bromide-anion-coordinated tin enolates in equilibrium between four-coordinated enolate 1c(e) and five-coordinated enolate 1c(h), showing a considerable upfield shift δ(119Sn) and increasing values of the coupling constants 1J(119Sn-13C). In detailed NMR analyses of highly coordinated tin enolate, it was shown that the contribution of highly coordinated species 1(h) to the equilibrium between 1(e) and 1(h) became more significant as the added amount of ligands such as Bu4NBr or HMPA was increased. Considering these results, it was assumed that the bromide-anion-coordinated tin enolate was generated, which showed a unique reactivity and selectivity. The effective control of chemoselectivity in the intermolecularly competitive reaction between organic halides and carbonyl compounds was demonstrated using two types of tin enolates, four-coordinated enolate and highly coordinated anionic enolate; halide displacement reaction exclusively took place using the bromide-anion-coordinated enolate, and the usual four-coordinated enolates reacted with only carbonyl compounds.
- Yasuda, Makoto,Hayashi, Keiko,Katoh, Yasuhiro,Shibata, Ikuya,Baba, Akio
-
p. 715 - 721
(2007/10/03)
-
- AUTOCONDENSATION OF CYCLOHEXANONE
-
Depending on the selected temperature and reaction conditions, the autocondensation of cyclohexanone can either be limited by the aldol condensation stage or can lead to the formation of a mixture of 2-(1-hydroxycyclohexyl)cyclohexanol, 2-cyclohexenylcyclohexanone, and 2-cyclohexylidenecyclohexanone.The aldol condensation takes place at a high rate and is reversible.The nature of the solvent does not affect the 2-cyclohexanone = 2-(1-hydroxycyclohexyl)cyclohexanone equilibrium.The addition of water to the reaction system inhibits the crotonization of 2-(1-hydroxycyclohexyl)cyclohexanone but does not affect the aldol condensation stage.
- Efimova, G. A.,Shutova, I. V.,Shapiro, Yu. E.,Efimov, V. A.,Turov, B. S.,Makarov, V. M.
-
p. 1081 - 1084
(2007/10/02)
-
- Reactions of Carbonyl Compounds with Grignard Reagents in the Presence of Cerium Chloride
-
The addition of Grignard reagents to ketones is significantly enhanced by cerium chloride with remarkable supression of side reactions, particularly enolization.Some esters, which are prone to side reactions, also react readily with Grignard reagents in the presence of cerium chloride to give normal reaction products in reasonable to high yields.
- Imamoto, Tsuneo,Takiyama, Noboyuki,Nakamura, Kimikazu,Hatajima, Toshihiko,Kamiya, Yasuo
-
p. 4392 - 4398
(2007/10/02)
-
- Deoxygenation and Desulfurization of Organic Compounds via Transition Metal Atom Cocondensation
-
Reactions resulting from the cocondensation of transition metal atoms with a variety of oxygen- and sulfur-containing organic compounds are surveyed.Alkenes are the major or exclusive volatile products when epoxides are reacted with Ti, V, Cr, Co, and Ni atoms. 2,6-Dimethylpyridine-N-oxide and dimethyl sulfoxide undergo deoxygenation upon cocondensation with chromium, but diisopropyl ether and decyl methyl ether do not.Dibenzyl ether yields bis(η6-dibenzyl ether)chromium(0) with Cr atoms, but dibenzyl sulfide undergoes desulfurization.Cyclohexanone and cycloheptanone afford low yields of reductive coupling and aldol products when cocondensed with Cr, Co, and Ni atoms.Nitro- and nitrosoarenes are deoxygenated to coupled azo and azoxy products with Cr atoms.Carbazole (3) is obtained from 2-nitrosobiphenyl, implicating nitrene or nitrenoid intermediates.Whereas isocyanides are not formed from isocyanates and metal atoms, they are produced when isothiocyanates are cocondensed with Cr and V atoms.
- Togashi, Shigeo,Fulcher, John G.,Cho, Bong Rae,Hasegawa, Minoru,Gladysz, J.A.
-
p. 3044 - 3053
(2007/10/02)
-