617-50-5Relevant academic research and scientific papers
Supercritical Carbon Dioxide. 5. Carboxyinversion Reactions of Diacyl Peroxides. Alkyl Group Rearrangement and CO2 Exchange
Sigman, Michael E.,Barbas, John T.,Leffler, John E.
, p. 1754 - 1757 (1987)
The decomposition of bis(isobutyryl) peroxide in supercritical Co2, CCl4, and CHCl3 gives both radical and ion pair-derived products in all three media.The rate constant in supercritical CO2 at 40 deg C, ?* -0.05, and density 0.93 is 3.6 * 10E-5 s-1.The rate constants in CCl4 and in CHCl3 at the same temperature are 7.72 * 10E-5 and 42.5 * 10E-5, respectively.The rate constant in CO2 fits a relationship with ?* observed for aromatic solvents.The products in CO2 include isopropyl isobutyryl carbonate (the carboxyinversion compound), 17percent yield, isopropyl isobutyrate, 5percent or less, and isobutyric acid, 17percent yield.There is no exchange of the inverted CO2 moiety of isopropyl isobutyryl carbonate for CO2 from the medium.The decomposition of cyclobutanecarbonyl m-chlorobenzoyl peroxide in CO2 is compared with the results reported by Taylor et al. (Taylor, K.G.; Govindan, C.K.; Kaelin, M.S.J.Am.Chem.Soc. 1979, 101, 2091) in conventional solvents.The rate constant for the decomposition of this peroxide in CO2 at 55 deg C at a density of 0.81 is 2.2 * 10E-5 s-1, in CCl4 it is 2.93 * 10E-5 s-1, and in CHCl3 it is 27.2 * 10E-5 s-1.The alkyl groups in the alkyl m-chlorobenzoate esters and alkyl m-chlorobenzoyl carbonates (carboxyinversion products) from this peroxide are rearranged in part to cyclopropylmethyl and 3-butenyl groups.The 13C of the carbonate carbonyl in the cyclopropylmethyl m-chlorobenzyl carbonate is about 12percent exchanged, but that from the carboxyinversion product with the unrearranged alkyl group is not exchanged.The effects of medium changes on the product are as follows: the change from CO2 to CCl4 increased the total yield of carboxyinversion compounds, but did not change the relative yields of the isomers appreciably.The further change in medium to CHCl3 drastically lowered the total yield of carboxyinversion compounds, again without changing the ratios of the isomers very much, and at the same time caused a large increase in the total yield of the esters.Both the ester yields and the rate appear to depend more on the hydrogen-bond-donor properties of the medium than on ?*.
Functionalization of saturated hydrocarbons by aprotic superacids 5. Regioselective carbonylation of propane in an organic solvent initiated by aprotic organic superacids CX4·nAlBr3 (X = Br, Cl; n = 1 or 2)
Akhrem,Orlinkov,Afanas'eva,Vol'pin
, p. 1154 - 1156 (1996)
Aprotic organic superacids CX4 · nAlBr3 (X = Br, Cl; n = 1 or 2) are effective initiators of carbonylation of propane with CO in an organic solvent at -10 to -20°C.
Ru-Catalyzed Transfer Hydrogenation of Nitriles, Aromatics, Olefins, Alkynes and Esters
Alshakova, Iryna D.,Gabidullin, Bulat,Nikonov, Georgii I.
, p. 4860 - 4869 (2018/10/02)
This paper reports the preparation of new ruthenium(II) complexes supported by a pyrazole-phosphine ligand and their application to transfer hydrogenation of various substrates. These Ru complexes were found to be efficient catalysts for the reduction of nitriles and olefins. Heterocyclic compounds undergo transfer hydrogenation with good to moderate yields, affording examples of unusual hydrogenation of all-carbon-rings. Internal alkynes with bulky substituents show selective reduction to olefins with the unusual E–selectivity. Esters with strong electron-withdrawing groups can be reduced to the corresponding alcohols, if ethanol is used as the solvent. Possible mechanisms of hydrogenation and olefin isomerization are suggested on the basis of kinetic studies and labelling experiments.
Transfer Hydrogenation of Nitriles, Olefins, and N-Heterocycles Catalyzed by an N-Heterocyclic Carbene-Supported Half-Sandwich Complex of Ruthenium
Mai, Van Hung,Nikonov, Georgii I.
, p. 943 - 949 (2016/05/09)
In the presence of KOBut, N-heterocyclic carbene-supported half-sandwich complex [Cp(IPr)Ru(pyr)2][PF6] (3) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) catalyzes transfer hydrogenation (TH) of nitriles, activated N-heterocycles, olefins, and conjugated olefins in isopropanol at the catalyst loading of 0.5%. The TH of nitriles leads to imines, produced as a result of coupling of the initially formed amines with acetone (produced from isopropanol), and showed good chemoselectivity. Reduction of N-heterocycles occurs for activated polycyclic substrates (e.g., quinoline) and takes place exclusively in the heterocycle. The TH also works well for linear and cyclic olefins but fails for trisubstituted substrates. However, the C = C bond of α,β-unsaturated esters, amides, and acids is easily reduced even for trisubstituted species, such as isovaleriates. Mechanistic studies suggest that the active species in these catalytic reactions is the trihydride Cp(IPr)RuH3 (5), which can catalyze these reactions in the absence of any base. Kinetic studies are consistent with a classical inner sphere hydride-based mechanism of TH.
Reactions of alkyl radicals with substituted toluenes and the effect of substituents on dissociation energies of benzyl C-H bonds
Arafat, Abdelfattah M.,Mathew, Samuel K.,Akintobi, Solademi O.,Zavitsas, Andreas A.
, p. 2226 - 2242 (2007/10/03)
Reactions of isopropyl and of undecyl radicals with meta- and para-substituted toluenes are reported. The results demonstrate that the reactivities of toluenes are due to both benzyl-H abstraction and addition of the alkyl radicals to the aromatic ring. Relative reactivities yield curved Hammett plots, consistent with kinetic data reported by Dutsch and Fischer. Abstractions and ring additions occur with comparable rates, but opposite Hammett slopes. Addition is favored by electron-withdrawing and abstraction by electron-donating substituents. The effects of substituents on the dissociation energies of benzyl C-H bonds are shown to be the major factor influencing reaction rates for benzyl-H abstraction by alkyl radicals.
Single-site anionic polymerization. Monomeric ester enolaluminate propagator synthesis, molecular structure, and polymerization mechanism
Rodriguez-Delgado, Antonio,Chen, Eugene Y.-X.
, p. 961 - 974 (2007/10/03)
The synthesis and molecular structure of the first examples of monomeric lithium ester enolaluminates that serve as structural models for single-site anionic propagating centers, as well as the mechanism of their polymerization of methacrylates catalyzed by conjugate organoaluminum Lewis acids, are reported. Reactions of isopropyl α-lithiolsobutyrate (2) with suitable deaggregating and stabilizing organoaluminum compounds such as MeAl(BHT)2 (BHT = 2,6-di-tert-butyl-4-methylphenolate) in hydrocarbons cleanly generate lithium ester enolaluminate complexes such as Li+[Me2C=C(O iPr)OAIMe(BHT)2]- (3). Remarkably, complex 3 is isolable and exists as a monomer in both solid and solution states. Unlike the uncontrolled polymerization of methacrylates by the aggregating enolate 2, the methacrylate polymerization by the monomeric 3 is controlled but exhibits low activity. However, the well controlled and highly active polymerization can be achieved by using the 3/MeAl(BHT)2 propagator/catalyst pair, which is conveniently generated by in situ mixing of 2 with 2 equiv of MeAl(BHT) 2. The structure of the added organoaluminum compounds has marked effects on the degree of monomer activation, enolaluminate formation and reactivity, and polymerization control. Kinetics of the polymerization by the 3/MeAl(BHT)2 pair suggest a bimolecular, activated-monomer anionic polymerization mechanism via single-site ester enolaluminate propagating centers. The molecular structures of activated monomer 1, aggregated initiator 2, and monomeric propagator 3 have been determined by X-ray diffraction studies.
Structure-function correlation in lipase catalysed esterification reactions of short and medium carbon chain length alcohols and acids
Divakar, Soundar
, p. 1919 - 1922 (2007/10/03)
An attempt has been made to correlate the carbon chain lengths of acids and alcohols to the extent of esterification in the Rhizomucor miehei lipase catalyzed esterification reactions involving acids of carbon chain length C2-C5 and alcohols of carbon chain length C1-C8.
Thermal Decomposition of Dialkoxyaluminum Carboxylates and Halocarboxylates
Stepovik,Zaburdaeva,Razuvaeva
, p. 1204 - 1209 (2007/10/03)
Thermal decomposition of diisopropoxyaluminum carboxylates (i-PrO)2AlOCOR (R = Pr, i-Pr, CH2Cl, CH2Br, CH2I, and CCl3) and i-PrOAl(OCOR)(OCOR') (R, R' = Me, Pr, i-Pr, i-Bu, and t-Bu) was studied. Diisopropoxyaluminum carboxylates derived from unsubstituted acids decompose to form mainly esters, whose yields decrease with increasing branching in the acid moiety. Thermolysis of diisopropoxyaluminum halocarboxylates yields esters and acetone as the product of oxidation of the alkoxy group.
The Esterification of Carboxylic Acid with Alcohol over Hydrous Zirconium Oxide
Takahashi, Kyoko,Shibagaki, Makoto,Matsushita, Hajime
, p. 2353 - 2361 (2007/10/02)
The esterification of carboxylic acids with alcohols proceeded efficienly with hydrous zirconium oxide to give the corresponding esters in the vapor phase, in the liquid phase, and in an autoclave.The steric hindrance of carboxylic acids and alcohols affected the esterification by lowering the reactivity.With a rise in the reaction temperature, the conversion of the carboxylic acid increased.The dehydration of alcohols was prevented by using hydrous zirconium oxide in spite of the high reaction temperature.The reaction rate is first-order with respect to the concentration of the catalyst and an alcohol and is inversely proportional to thta of the carboxylic acid.Transesterification also proceeded efficiently.
Selective activation of olefinic C-H bonds. Reaction of a hydridomolybdenum complex with methacrylic esters to form hydrido-alkenyl complexes
Ito, Takashi,Tosaka, Hisao,Yoshida, Shun-Ji,Mita, Katsuhisa,Yamamoto, Akio
, p. 735 - 739 (2008/10/08)
MoH4(dppe)2 (dppe = Ph2PCH2CH2PPh2) (1) reacted thermally or photochemically with an excess of alkyl methacrylates to give red complexes which analyzed as MoH[CH=C(CH3)C(O)OR] (dppe)2 (2, R = C2H5, i-C3H7, n-C4H9, and c-C6H11) together with H2 and alkyl isobutyrates. Seven-coordinate complexes 2 were spectroscopically characterized and were found to be stereochemically nonrigid on the basis of temperature-dependent 31P{1H} NMR spectra. The mechanism of the formation of 2 and its intramolecular exchange process are discussed.
