28746-99-8Relevant academic research and scientific papers
BIS(BROMOMAGNESIO)TRIMETHYLSILYLMETHANE
Heisteeg, B. J. J. van de,Schat, G.,Tinga, M. A. G. M.,Akkerman, O. S.,Bickelhaupt, F.
, p. 6123 - 6124 (1986)
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).
Hydrogen-Catalyzed Acid Transformation for the Hydration of Alkenes and Epoxy Alkanes over Co-N Frustrated Lewis Pair Surfaces
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)
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.
Reactivity of Lithium β-Ketocarboxylates: The Role of Lithium Salts
Berton, Mateo,Mello, Rossella,Williard, Paul G.,González-Nú?ez, María Elena
supporting information, p. 17414 - 17420 (2017/12/15)
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.
Synthesis of sulphur-modified bifunctional hydrotalcites and study of their surface characteristics by inverse gas chromatography
Ren, Xiaoqian,Hu, Xi,Zhang, Feng,Wang, Junge,Liang, Jinhua,Wu, Wenliang,Jiang, Min,Wang, Jun
, p. 4813 - 4820 (2015/10/05)
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.
Mass spectrometric studies of self-condensation products of cyclohexanone under alkaline conditions and synthesis of dodecahydrotriphenylene and triphenylene from easily available reactants
Kovalev,Kopchuk,Zyryanov,Khasanov,Rusinov,Chupakhin
, p. 1539 - 1542 (2015/03/14)
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.
A selective solvent-free self-condensation of carbonyl compounds utilizing microwave irradiation
Sharma, Lalit Kumar,Kim, Kyung Bo,Elliott, Gregory I.
supporting information; experimental part, p. 1546 - 1549 (2011/07/31)
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.
Thermodynamic properties for 2-(1′-hydroxycyclohexyl)cyclohexanone and equilibrium of dimerization of cyclohexanone
Shevelyova, Marina P.,Kabo, Gennady J.,Blokhin, Andrey V.,Kabo, Audrey G.,Jursha, Joseph A.,Rajko, Anna A.
, p. 40 - 45 (2007/10/03)
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.
Thermodynamics of 2-(1′-hydroxycyclohexyl)cyclohexanone: Vaporization, sublimation, and the ideal gas state thermodynamic properties
Shevelyova, Marina P.,Zaitsau, Dzmitry H.,Paulechka, Yauheni U.,Kabo, Gennady J.,Verevkin, Sergey P.
, p. 1946 - 1952 (2007/10/03)
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.
The boron-mediated ketone-ketone aldol reaction
Cergol, Katie M.,Turner, Peter,Coster, Mark J.
, p. 1505 - 1509 (2007/10/03)
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.
Chemoselective aldol condensation in 5 mol dm 3 lithium perchlorate-nitromethane. A comparison with lithium perchloratediethyl ether medium
Sudha,Sankararaman
, p. 383 - 386 (2007/10/03)
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.
