16664-07-6Relevant academic research and scientific papers
Deciphering Reactivity and Selectivity Patterns in Aliphatic C-H Bond Oxygenation of Cyclopentane and Cyclohexane Derivatives
Martin, Teo,Galeotti, Marco,Salamone, Michela,Liu, Fengjiao,Yu, Yanmin,Duan, Meng,Houk,Bietti, Massimo
supporting information, p. 9925 - 9937 (2021/06/30)
A kinetic, product, and computational study on the reactions of the cumyloxyl radical with monosubstituted cyclopentanes and cyclohexanes has been carried out. HAT rates, site-selectivities for C-H bond oxidation, and DFT computations provide quantitative information and theoretical models to explain the observed patterns. Cyclopentanes functionalize predominantly at C-1, and tertiary C-H bond activation barriers decrease on going from methyl- and tert-butylcyclopentane to phenylcyclopentane, in line with the computed C-H BDEs. With cyclohexanes, the relative importance of HAT from C-1 decreases on going from methyl- and phenylcyclohexane to ethyl-, isopropyl-, and tert-butylcyclohexane. Deactivation is also observed at C-2 with site-selectivity that progressively shifts to C-3 and C-4 with increasing substituent steric bulk. The site-selectivities observed in the corresponding oxidations promoted by ethyl(trifluoromethyl)dioxirane support this mechanistic picture. Comparison of these results with those obtained previously for C-H bond azidation and functionalizations promoted by the PINO radical of phenyl and tert-butylcyclohexane, together with new calculations, provides a mechanistic framework for understanding C-H bond functionalization of cycloalkanes. The nature of the HAT reagent, C-H bond strengths, and torsional effects are important determinants of site-selectivity, with the latter effects that play a major role in the reactions of oxygen-centered HAT reagents with monosubstituted cyclohexanes.
Synthesis, structural characterization and C–H activation property of a tetra-iron(III) cluster
Dey, Dhananjay,Patra, Moumita,Al-Hunaiti, Afnan,Yadav, Hare Ram,Al-mherat, Afrah,Arar, Sharif,Maji, Milan,Choudhury, Angshuman Roy,Biswas, Bhaskar
, p. 220 - 226 (2019/01/05)
A non-heme tetra-iron cluster, [Fe4 III(μ-O)2(μ-OAc)6(2,2′-bpy)2(H2O)2](NO3 ?)(OH?) (1), [OAc = acetate; 2,2′-bpy = 2,2′-bipyridine] containing oxido- and acetato-bridges was synthesized and structurally characterized by different spectroscopic methods including single crystal X-ray diffraction studies. X-ray crystal structure analysis of 1 revealed that tetra-iron complex was crystallized in monoclinic system with C2/c space group. Each of the Fe centres in 1 was found to exist in octahedral geometry and interconnected by oxido- and acetato-bridges. Bond valence sum (BVS) calculation recommended the existence of iron centres in +3 oxidation state. Variable temperature magnetic measurement authenticated the dominating antiferromagnetic ordering among the iron centres in the solid state of 1. This tetra-iron cluster was also evaluated as an efficient catalytic system towards the oxidation of both linear & cyclic alkanes without production of primary C–H bond oxidation products. Oxidation of secondary C–H bonds attested the formation of both the corresponding alcohols & ketones in 27–900 TONs. The tetra-iron catalytic system with Alcohol/Ketone values 0.2–1.7 indicated the involvement of freely diffusing carbon-centered radicals rather than metal based oxidant.
Selective hydrogenation of arenes to cyclohexanes in water catalyzed by chitin-supported ruthenium nanoparticles
Morioka, Yuna,Matsuoka, Aki,Binder, Kellie,Knappett, Benjamin R.,Wheatley, Andrew E.H.,Naka, Hiroshi
, p. 5801 - 5805 (2016/08/06)
The selective hydrogenation of aromatic compounds to cyclohexanes was found to be promoted by chitin-supported ruthenium nanoparticles (Ru/chitin) under near-neutral, aqueous conditions without the loss of C-O/C-N linkages at benzylic positions.
Readily Accessible Bulky Iron Catalysts exhibiting Site Selectivity in the Oxidation of Steroidal Substrates
Font, David,Canta, Mercè,Milan, Michela,Cussó, Olaf,Ribas, Xavi,Klein Gebbink, Robertus J. M.,Costas, Miquel
supporting information, p. 5776 - 5779 (2016/05/09)
Bulky iron complexes are described that catalyze the site-selective oxidation of alkyl C-H bonds with hydrogen peroxide under mild conditions. Steric bulk at the iron center is introduced by appending trialkylsilyl groups at the meta-position of the pyridines in tetradentate aminopyridine ligands, and this effect translates into high product yields, an enhanced preferential oxidation of secondary over tertiary C-H bonds, and the ability to perform site-selective oxidation of methylenic sites in terpenoid and steroidal substrates. Unprecedented site selective oxidation at C6 and C12 methylenic sites in steroidal substrates is shown to be governed by the chirality of the catalysts.
Cytochrome P450 catalyzed oxidative hydroxylation of achiral organic compounds with simultaneous creation of two chirality centers in a single C-H activation step
Roiban, Gheorghe-Doru,Agudo, Ruben,Reetz, Manfred T.
supporting information, p. 8659 - 8663 (2014/08/18)
Regio- and stereoselective oxidative hydroxylation of achiral or chiral organic compounds mediated by synthetic reagents, catalysts, or enzymes generally leads to the formation of one new chiral center that appears in the respective enantiomeric or diastereomeric alcohols. By contrast, when subjecting appropriate achiral compounds to this type of C-H activation, the simultaneous creation of two chiral centers with a defined relative and absolute configuration may result, provided that control of the regio-, diastereo-, and enantioselectivity is ensured. The present study demonstrates that such control is possible by using wild type or mutant forms of the monooxygenase cytochrome P450 BM3 as catalysts in the oxidative hydroxylation of methylcyclohexane and seven other monosubstituted cyclohexane derivatives.
CO2 promoted hydrogenolysis of benzylic compounds in methanol and water
Lin, Hsin-Wei,Yen, Clive H.,Hsu, Han,Tan, Chung-Sung
, p. 17222 - 17227 (2013/09/24)
This study successfully demonstrated the hydrogenolysis of benzylic alcohols and their derivatives over a Pd/C catalyst by using CO 2-expanded methanol (CX-methanol) and compressed CO2/water as two green reaction media. It was found that with the addition of low-pressure CO2 (1 MPa), the reaction conversions of benzylic alcohols and their derivatives could all be increased in the CO2 promoted systems. For example, the conversion of 1-phenylethanol could be elevated from 23% to 63% in CX-methanol and the conversion of benzyl alcohol could be elevated from 75% to 92% in compressed CO2/water. The positive effects of CO2 could be attributed to the decrease of mass transfer resistance and the increase of hydrogen solubility. CO2 could also form methylcarbonic acid and carbonic acid in methanol and water, respectively. Therefore, it could enhance the departing ability of the protonated hydroxyl leaving groups by providing a more acidic environment. In addition, the hydrogenolysis (or deoxygenation) of aromatic aldehyde and ketone by using compressed CO2/water as the solvent were also studied in this work. The results suggested that both CX-methanol and compressed CO 2/water could be used as two efficient solvents for the hydrogenolysis reactions.
Organic processes initiated by non-classical energy sources
Nuechter, Matthias,Ondruschka, Bernd,Jungnickel, Anja,Mueller, Ute
, p. 579 - 586 (2007/10/03)
Non-classical energy sources such as microwave energy, ultrasound and mechanoenergy and their combination with UV-VIS radiation are new tools in synthetic chemistry and chemical processing. Here we describe the application of microwave treatment for selected organic reactions such as (i) enzymatic transesterification of optically active alcohols, (ii) mercury-sensitized gas-phase photolysis of hydrocarbons in the microwave field, (iii) environmentally benign oxidations of olefins and (iv) the application of mechanoenergy separately and in combination with microwave irradiation for special oxidation reactions. Copyright
Photolysis of Alcohols and Alkanones in Acetone Solutions. Photochemical Cycloaddition Reaction between Acetone and Aliphatic Enols
Shimizu, Nobujiro,Miyahara, Toru,Mishima, Masaaki,Tsuno, Yuho
, p. 2032 - 2039 (2007/10/02)
Transient enols including those of acetaldehyde, acetone, cyclopentanone, 3-pentanone, 2,4-dimethyl-3-pentanone, 2-butanone, and 2-methyl-3-pentanone were trapped photochemically with acetone via a cycloaddition and isolated as corresponding 3-oxetanols in reasonable yields in the photolysis of six different secondary alcohols and two alkanones, 3-octanone and hexanal, in acetone solutions.The trapping experiments indicated the photodehydrogenation of unsymmetrical alcohols, 2-butanol and 2-methyl-3-pentanol, in acetone to be highly regioselective in preference for the formation of the less alkylated enol.
Hydroboration. 79. Preparation and Properties of Methylborane and Dimethylborane and Their Characteristics as Hydroborating Agents. Synthesis of Tertiary Alcohols Containing Methyl Groups via Hydroboration.
Brown, Herbert C.,Cole, Thomas E.,Srebnik, Morris,Kim, Kee-Won
, p. 4925 - 4930 (2007/10/02)
Lithium methylborohydride and lithium dimethylborohydride are readily prepared from the corresponding boronic and borinic esters.Methylborane and dimethylborane are cleanly liberated from these borohydrides by protonation with hydrogen chloride in ether, thus permitting the ready liberation of these methylboranes from the stable methylborohydrides.In contrast to the earlier gas-phase studies, methylborane in solution is remarkably stable to disproportionation, forming a strong dimer complex.However, dimethylborane in solution is less stable, undergoing some disproportionation at room temperature.By liberating these boranes in appropriate solvents in the presence of the alkenes, the redistribution can be controlled and a satisfactory preparation of dialkylmethylboranes achieved.These organoboranes can be carbonylated-oxidized to form the corresponding tertiary alcohols containing one or two methyl groups, the first time these valuable derivatives have been available via hydroboration.Gas chromatographic examination of these tertiary alcohols established the absence of significant redistribution.The regioselectivity of these two new hydroborating agents was investigated with representative alkenes, and excellent selectivities with terminal and trisubstituted alkenes were achieved.
