936-99-2Relevant articles and documents
Carbonyl 1,2-transposition through triflate-mediated a-amination
Wu, Zhao,Xu, Xiaolong,Wang, Jianchun,Dong, Guangbin
, p. 734 - 740 (2021/11/16)
To date, it remains challenging to selectively migrate a carbonyl oxygen within a given molecular scaffold, especially to an adjacent carbon. In this work, we describe a simple one- or two-pot protocol that transposes a ketone to the vicinal carbon. This approach first converts the ketone to the corresponding alkenyl triflate, which can then undergo the palladium- and norbornene-catalyzed regioselective a-amination and ipso-hydrogenation enabled by a bifunctional hydrogen and nitrogen donor. The resulting "transposed enamine" intermediate can subsequently be hydrolyzed to produce the 1,2-carbonyl-migrated product. This method allows rapid access to unusual bioactive analogs through late-stage functionalization.
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.
Lewis acid activation of fragment-coupling reactions of tertiary carbon radicals promoted by visible-light irradiation of EDA complexes
Pitre, Spencer P.,Allred, Tyler K.,Overman, Larry E.
supporting information, p. 1103 - 1106 (2021/02/16)
The addition of tertiary carbon radicals generated from N-(acyloxy)phthalimide esters to cyclic α,β-unsaturated ketones and lactones is markedly enhanced by the addition of substoichiometric amounts of a Ln(OTf)3. The reaction is accomplished by irradiation with visible light in the absence of a photosensitizer and is suggested to proceed by excitation of a ternary electron donor?acceptor complex between the NHPI ester, Hantzsch ester, and a Ln(OTf)3
Efficient Aliphatic C-H Oxidation and C═C Epoxidation Catalyzed by Porous Organic Polymer-Supported Single-Site Manganese Catalysts
Wang, Bingyang,Lin, Jin,Sun, Qiangsheng,Xia, Chungu,Sun, Wei
, p. 10964 - 10973 (2021/09/08)
Bioinspired manganese complexes have emerged over recent decades as attractive catalysts for a number of selective oxidation reactions. However, these catalysts still suffer from oxidative degradation. In the present study, we prepared a series of porous Mn-N4 catalysts in which the catalytic units are embedded in the skeleton of porous organic polymers (POPs). These POP-based manganese catalysts demonstrated high reactivity in the oxidation of aliphatic C-H bonds and the asymmetric epoxidation of olefins. Furthermore, these catalysts could be readily recycled and reused due to their heterogeneous nature. Morphological characterization revealed that the Mn-N4 complex was individually distributed over a porous polymer network. Remarkably, the nature of the single-site catalyst prevented oxidative degradation during the reaction. The present work has thus developed a successful approach for bioinspired single-site manganese catalysts in which the oxidation reaction is confined to a specific channel in an enzyme-like mode.
Sonochemical Preparation of Dipicolinamide Mn-complexes and Their Application as Catalysts Towards Sono-synthesis of Ketones
Arafa, Wael A. A.
, p. 1403 - 1412 (2019/02/25)
A series of non-heme Mn-complexes has been synthesized by the sonication of manganese (II)chloride and bis-amides (condensation products of 2-picolinic acid and o-phenylenediamines). The Mn-complexes effectively promote the oxidation of unactivated aliphatic and benzylic C─H and N-bearing heterocycles substrates with low catalyst loading using eco-friendly hydrogen peroxide in the presence of acetic acid as additive under ultrasonic irradiation. Chromatographic studies revealed that the corresponding ketones are the only detectable products. Noteworthy, the presence of electron donors in the catalyst structure significantly increased the reaction yields. The substantial lowering of the oxidation reaction yields by adding ionol (2,6-di-tert-butyl-4-methylphenol) as a free radical trap suggesting a free radical reaction pathway.
Iron-catalyzed oxidative functionalization of C(sp3)-H bonds under bromide-synergized mild conditions
Yu, Han,Zhao, Qixin,Wei, Zheyu,Wu, Zhikang,Li, Qi,Han, Sheng,Wei, Yongge
supporting information, p. 7840 - 7843 (2019/07/12)
An efficient oxidation and functionalization of C-H bonds with an inorganic-ligand supported iron catalyst and hydrogen peroxide to prepare the corresponding ketones was achieved using the bromide ion as a promoter. Preliminary mechanistic investigations indicated that the bromide ion can bind to FeMo6 to form a supramolecular species (FeMo6·2Br), which can effectively catalyze the reaction.
Selective C(sp3)?H Aerobic Oxidation Enabled by Decatungstate Photocatalysis in Flow
Laudadio, Gabriele,Govaerts, Sebastian,Wang, Ying,Ravelli, Davide,Koolman, Hannes F.,Fagnoni, Maurizio,Djuric, Stevan W.,No?l, Timothy
supporting information, p. 4078 - 4082 (2018/03/21)
A mild and selective C(sp3)?H aerobic oxidation enabled by decatungstate photocatalysis has been developed. The reaction can be significantly improved in a microflow reactor enabling the safe use of oxygen and enhanced irradiation of the reaction mixture. Our method allows for the oxidation of both activated and unactivated C?H bonds (30 examples). The ability to selectively oxidize natural scaffolds, such as (?)-ambroxide, pregnenolone acetate, (+)-sclareolide, and artemisinin, exemplifies the utility of this new method.
Efficient Aliphatic C?H Bond Oxidation Catalyzed by Manganese Complexes with Hydrogen Peroxide
Wang, Wenfang,Xu, Daqian,Sun, Qiangsheng,Sun, Wei
supporting information, p. 2458 - 2464 (2018/04/02)
A tetradentate nitrogen ligand containing a benzimidazole ring and an electron-rich pyridine ring was developed, the resulting manganese complex exhibited good activity in the C?H oxidation of simple alkanes. In particular, cyclic aliphatic alkanes were transformed into ketones in very good yields (up to 89 %) by using environmentally benign H2O2 as the terminal oxidant. This protocol was also applied successfully in benzylic C?H oxidation, giving the corresponding ketones with very good selectivities. In addition, tertiary C?H bond oxidation of complex molecules by the manganese complex showed potential utility for assembling alcohols with good selectivity in late-stage chemical synthesis.
From DNA to catalysis: A thymine-acetate ligated non-heme iron(III) catalyst for oxidative activation of aliphatic C-H bonds
Al-Hunaiti, Afnan,R?is?nen, Minn?,Repo, Timo
supporting information, p. 2043 - 2046 (2016/02/05)
A non-heme, iron(iii)/THA(thymine-1-acetate) catalyst together with H2O2 as an oxidant is efficient in oxidative C-H activation of alkanes. Although having a higher preference for tertiary C-H bonds, the catalyst also oxidizes aliphatic secondary C-H bonds into carbonyl compounds with good to excellent conversions. Based on the site selectivity of the catalyst and our mechanistic studies the reaction proceeds via an Fe-oxo species without long lived carbon centered radicals.
Efficient benzylic and aliphatic C-H oxidation with selectivity for methylenic sites catalyzed by a bioinspired manganese complex
Shen, Duyi,Miao, Chengxia,Wang, Shoufeng,Xia, Chungu,Sun, Wei
supporting information, p. 1108 - 1111 (2014/03/21)
A benzimidazole-based nonheme manganese complex efficiently catalyzes benzylic, aliphatic C-H as well as tertiary C-H oxidation with hydrogen peroxide as the oxidant in the presence of acetic acid as additive. 18O labeling experiments suggest the reaction may proceed via a high-valent manganese-oxo intermediate.
