10487-96-4Relevant articles and documents
Side Chain Hydroxylation of Aromatic Compounds by Fungi. Part 5. Exploring the Benzylic Hydroxylase of Mortierella isabellina
Holland, Herbert L.,Kindermann, Maik,Kumaresan, Sudalaiyandi,Stefanac, Tomislav
, p. 1353 - 1364 (1993)
The active site topography of the hydroxylase enzyme of Mortierella isabellina ATCC 42613, which carries out the benzylic hydroxylation of toluene, ethylbenzene, and related compounds, has been explored.Operating in a whole cell biotransformation mode, this enzyme shows selectivity in substrate processing based on the nature, position and size of substituent side chains close to the site of hydroxylation.The results of determination of the yield and stereochemistry of hydroxylation of over twenty substrates and potential substrates, together with previously reported data, have been used to propose an active site model for the benzylic hydroxylase enzyme.
Photoreaction of valerophenone in aqueous solution
Zepp,Gumz,Miller,Gao
, p. 5716 - 5723 (1998)
Kinetics and products of the photoreaction of the phenyl ketone valerophenone were investigated as a function of temperature, pH, and wavelength in aqueous solution. Under these conditions (-4M), the photoreactions are pseudo-first-order with respect to valerophenone concentration. Type II quantum yields for photoreaction were close to unity throughout the 290-330 nm spectral region and in the temperature range from 10 to 40 °C. The quantum yields for the photoproducts were 0.65 ± 0.04 for cleavage to acetophenone and propene and an overall yield of 0.32 ± 0.03 for cyclization to two cyclobutanols at 20 °C. A small amount of 1-phenylcyclopentanol (2% yield) also was formed. These photoreactions were quenchable by additions of the triplet quenchers sorbic alcohol or sorbic acid, and Stern-Volmer plots were linear up to at least 80% quenching of the photoreactions. On the basis of quenching studies with steady-state irradiations, the triplet lifetime of valerophenone at 20 °C was estimated to be 52 ns, 7 times longer than that observed in hydrocarbon solvents. Since the triplet lifetime is controlled by intramolecular hydrogen abstraction, these results indicate that the rate constant for H abstraction is significantly lowered in aqueous media. The slower H abstraction in aqueous solution is attributed to stabilization of the excited π,π* state by water and vibronic mixing and slight inversion of the reactive n,π* triplet and the unreactive π,π* triplet states. This interpretation also is supported by changes in the UV absorption spectra of phenyl ketones in water compared to organic solvents. Red shifts, compared to the polar organic solvent acetonitrile, were observed in the π-π* transitions of valerophenone and acetophenone, reflecting stabilization of the excited π,π* state by water. Other results indicated that the quantum yields for valerophenone photoreaction are pH-independent from pH 9 to pH 2 but decrease significantly below pH 2. The decrease at low pH is attributed to quenching of triplet reactivity via protonation of the excited triplet state. The use of valerophenone as a convenient actinometer for studies in water is discussed; its half-lives during midday exposure to summer sunlight in temperate latitudes are 30 min.
13C NMR spectroscopic comparison of sterically stabilized meta and para-substituted o-tolyldi(adamant-l-yl)methyl cations with conjugatively stabilized benzyl cations
Lomas, John S.
, p. 2601 - 2609 (1996)
A series of meta- and para-substituted anti-o-tolyldi(adamant-1-yl)methyl cations has been generated by reaction of anti-o-tolyldi(adamant-1-yl)methanols with trifluoroacetic acid in chloroform. 13C NMR spectroscopy indicates small but significant variations in the chemical shifts of the charged carbon and its nearest neighbours on the adamantyl groups, and departures from additivity of substituent effects on the shifts of the aromatic carbons. Previous work on the closely related di(adamant-1-yl)benzyl cations is discussed. Comparison with data on aryl-substituted carbocations in superacid media reveals marked differences in the aromatic carbon shifts in the two types of carbocation. The dihedral angle between aryl and carbocation planes in aryldi(adamant-1-yl)methyl cations is estimated to be about 60°.
Synthesis of 1-Pyrroline by Denitrogenative Ring Expansion of Cyclobutyl Azides under Thermal Conditions
Ban, Kazuho,Miki, Yuya,Sajiki, Hironao,Sawama, Yoshinari,Tomita, Naohito
supporting information, p. 3481 - 3484 (2021/06/17)
We herein report an efficient and systematic synthesis of 1-pyrrolines from cyclobutyl azides under thermal and neutral conditions. The reaction proceeded without any additional reagents, and nitrogen was generated as the sole by-product. Furthermore, the generated 1-pyrrolines could be continuously transformed into pyrroles, N-Boc-amines, and oxaziridines in an one-pot manner. (Figure presented.).
Electrophotochemical Ring-Opening Bromination oftert-Cycloalkanols
Yamamoto, Kosuke,Toguchi, Hiroyuki,Kuriyama, Masami,Watanabe, Shin,Iwasaki, Fumiaki,Onomura, Osamu
, p. 16177 - 16186 (2021/09/13)
An electrophotochemical ring-opening bromination of unstrainedtert-cycloalkanols has been developed. This electrophotochemical method enables the oxidative transformation of cycloalkanols with 5- to 7-membered rings into synthetically useful ω-bromoketones without the use of chemical oxidants or transition-metal catalysts. Alkoxy radical species would be key intermediates in the present transformation, which generate through homolysis of the O-Br bond in hypobromite intermediates under visible light irradiation.
Cu-Catalyzed: O -alkylation of phenol derivatives with alkylsilyl peroxides
Sakurai, Shunya,Kano, Taichi,Maruoka, Keiji
supporting information, p. 81 - 84 (2021/01/14)
A Cu-catalyzed O-alkylation of phenol derivatives using alkylsilyl peroxides as alkyl radical precursors is described. The reaction proceeds smoothly under mild reaction conditions and the use of two different ligands with a Cu catalyst provides a wide range of products. A mechanistic study suggested that the reaction proceeds via a radical mechanism. This journal is
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.
Supramolecularly regulated copper-bisoxazoline catalysts for the efficient insertion of carbenoid species into hydroxyl bonds
Iniesta, Ester,Vidal-Ferran, Anton
supporting information, p. 6364 - 6367 (2020/06/21)
The catalytic insertion of copper carbenoids into O-H bonds affords synthetically useful α-alkyl/aryl-α-alkoxy/aryloxy derivatives. Herein, the design, preparation and application of supramolecularly regulated copper(i) complexes of bisoxazoline ligands is reported. We have demonstrated that the catalytic performance of these systems can be modulated by the use of an external molecule (i.e.the regulation agent), which interacts with a polyethyleneoxy chain on the ligand (i.e.the regulation site)viasupramolecular interactions. This approach has been applied to an array of structurally diverse alcohols (cycloalkyl, alkyl and aryl derivatives). Moreover, we have used this methodology to synthesise advanced synthetic intermediates of biologically relevant compounds.
Triphosgene and DMAP as Mild Reagents for Chemoselective Dehydration of Tertiary Alcohols
Ganiu, Moshood O.,Cleveland, Alexander H.,Paul, Jarrod L.,Kartika, Rendy
supporting information, p. 5611 - 5615 (2019/08/01)
The utility of triphosgene and DMAP as mild reagents for chemoselective dehydration of tertiary alcohols is reported. Performed in dichloromethane at room temperature, this reaction is readily tolerated by a broad scope of substrates, yielding alkenes preferentially with the (E)-geometry. While formation of the Hofmann products is generally favored, a dramatic change in alkene selectivity toward the Zaitzev products is observed when the reaction is carried out in dichloroethane at reflux.
Manganese-catalyzed ring-opening carbonylation of cyclobutanol derivatives
Meyer, Tim,Yin, Zhiping,Wu, Xiao-Feng
supporting information, p. 864 - 867 (2019/02/20)
Herein, we report a manganese-catalyzed ring-opening carbonylation of cyclobutanol derivatives through cyclic C–C bond cleavage. The reaction happens via a radical-mediated pathway to selectively generate 1,5-ketoesters. A variety of substrates with subst
