30407-41-1Relevant academic research and scientific papers
Catalytic oxidation of primary c-h bonds in alkanes with bioinspired catalysts
Dantignana, Valeria,Company, Anna,Costas, Miquel
, p. 470 - 477 (2020)
Catalytic oxidation of primary C-H bonds of alkanes with a series of iron and manganese catalysts is investigated. Products resulting from oxidation of methylenic sites are observed when hexane (S1) is used as model substrate, while corresponding primary C-H bonds remain unreactive. However, by using 2,2,3,3-tetra-methylbutane (S2) as model substrate, which only contains primary alkyl C-H bonds, oxidation takes place catalytically using a combination of hydrogen peroxide, a manganese catalyst and acetic acid as co-catalyst, albeit with modest yields (up to 4.4 TON). Complexes bearing tetradentate aminopyridine ligands provide the best yields, while a related pentadentate ligand provides smaller product yields. The chemoselectivity of the reaction is solvent dependent. Carboxylic acid 2b is observed as major product when the reaction takes place in acetonitrile, because of the facile overoxidation of the first formed alcohol product 2a. Instead the corresponding primary alcohol 2a becomes dominant in reactions performed in 2,2,2-trifluoroethanol (TFE). Polarity reversal of the hydroxyl moiety arising from the strong hydrogen bond donor ability of the latter solvent accounts for the unusual product chemoselectivity of the reaction. The significance of the current results in the context of light alkane oxidation is discussed.
Understanding reactivity and stereoselectivity in palladium-catalyzed diastereoselective sp3 C-H Bond activation: Intermediate characterization and computational studies
Giri, Ramesh,Lan, Yu,Liu, Peng,Houk,Yu, Jin-Quan
, p. 14118 - 14126 (2012)
The origin of the high levels of reactivity and diastereoselectivity (>99:1 dr) observed in the oxazoline-directed, Pd(II)-catalyzed sp 3 C-H bond iodination and acetoxylation reactions as reported in previous publications has been studied and explained on the basis of experimental and computational investigations. The characterization of a trinuclear chiral C-H insertion intermediate by X-ray paved the way for further investigations into C-H insertion step through the lens of stereochemistry. Computational investigations on reactivities and diastereoselectivities of C-H activation of t-Bu- and i-Pr-substituted oxazolines provided good agreement with the experimental results. Theoretical predictions with DFT calculations revealed that C-H activation occurs at the monomeric Pd center and that the most preferred transition state for C-H activation contains two sterically bulky t-Bu substituents in anti-positions due to steric repulsion and that this transition state leads to the major diastereomer, which is consistent with the structure of the newly characterized C-H insertion intermediate. The structural information about the transition state also suggests that a minimum dihedral angle between C-H bonds and Pd-OAc bonds is crucial for C-H bond cleavage. We have also utilized density functional theory (DFT) to calculate the energies of various potential intermediates and transition states with t-Bu- and i-Pr-substituted oxazolines and suggested a possible explanation for the substantial difference in reactivity between the t-Bu- and i-Pr-substituted oxazolines.
CATALYTICS ASYMMETRIC ACTIVATION OF UNACTIVATED C-H BONDS, AND COMPOUNDS RELATED THERETO
-
Page/Page column 76-77; 89-90, (2010/10/20)
One aspect of the present invention is directed in part to catalytic and stereoselective functionalization of unactivated C-H bonds of simple organic substrates. The compounds and methods provided herein allow one to control the stereochemistry in a C-H activation step, activate substrates containing α-hydrogens next to the directing group, and remove a directing group under mild conditions. One aspect of the present invention relates to a transition-metal-catalyzed method for selective and asymmetric oxidation of carbons located in a β- or γ-position relative to an auxiliary. Another aspect of the invention relates to the enantiomerically-enriched substrates and the enantiomerically-enriched products formed via said method. In certain embodiments, oxazoline and oxazinone directing groups are used. In addition, the Boc protecting group has been identified as a directing group which does not necessitate removal.
Analogs of isovaleramide, a pharmaceutical composition including the same, and a method of treating central nervous system conditions or diseases
-
Page/Page column 9, (2010/02/15)
An isovaleramide analog having at least one of an increased potency, an increased half-life, and an increased stability compared to isovaleramide. The isovaleramide analog is a cyclic analog or a noncyclic analog. The isovaleramide analog is formulated into a pharmaceutical composition. A method of treating a central nervous system condition or disease is also disclosed. The method comprises administering an isovaleramide analog to a patient suffering from the central nervous system condition or disease.
Conformational Analysis and Stereodynamics of Primary Acyclic Alkyl Radicals by EPR Spectroscopy
Ingold, K. U.,Nonhebel, D. C.,Walton, J. C.
, p. 2859 - 2869 (2007/10/02)
The EPR spectra of n-alkyl, 2-methylalkyl, 2,2-dimethylalkyl, 2,2,3-trimethylbutyl, and 2,2,3,3-tetramethylbutyl radicals indicate that at 90 K they exist in "rigid" conformations with respect to rotation about the Cβ-Cγ bonds.The preferred conformations about the Cα-Cβ and Cβ-Cγ bonds were deduced by analysis of the β- and γ-H hyperfine splittings (hfs). 2,2,3,3-Tetramethylbutyl radicals, the only radicals with a CH3 group approximately all-trans with respect to the semioccupied p-orbital, were also the only radicals to show resolved δ-hfs.The barriers to internal rotation of the methyl groups in n-propyl, isobutyl, neopentyl, 2,2-bis(trideuteriomethyl)butyl, and 2,2,3,3-tetramethylbutyl radicals were obtained by line shape analysis; the ethyl rotation barrier in 2,2-bis(trideuteriomethyl)butyl and the tert-butyl rotation barrier in 2,2,3,3-tetramethylbutyl radicals were estimated in a similar way.The experimental hfs of trans γ-hydrogens were shown to fit a relationship of the form aHγ = 0.1 +7.9 cos2 Φ, where Φ is the dihedral angle between the SOMO and the plane through Cα, Cβ, and Cγ.Trends in the internal rotation barriers of the alkyl groups were adequately accounted for in terms of steric effects.
Lewis Acid-mediated α-tert-Alkylation of Carboxylic Acids and Carboxylic Esters
Reetz, Manfred T.,Schwellnus, Konrad,Huebner, Friedhelm,Massa, Werner,Schmidt, Roland E.
, p. 3708 - 3724 (2007/10/02)
Carboxylic acids and carboxylic esters can be α-tert-alkylated via the corresponding ketene silyl acetals 2 and 4 using tertiary alkyl halides or acetates in the presence of ZnCl2.The method is successful even if the products are sterically strained due t
