591-24-2Relevant academic research and scientific papers
Radical anion ring opening reactions via photochemically induced electron transfer
Cossy,Aclinou,Bellosta,Furet,Baranne-Lafont,Sparfel,Souchaud
, p. 1315 - 1316 (1991)
Ketyl radical anions can induce the opening of adjacent strained ring such as cyclopropane, cyclobutane, epoxide and 7-oxabicyclo[2.2.1]hepane.
Copper-catalyzed highly enantioselective 1,4-conjugate addition of trimethylaluminum to 2-cyclohexenone
Ciang, Liang,Chan, Albert S.C.
, p. 1393 - 1396 (2002)
New bidentate phosphites were prepared starting from BINOL and H8-BINOL. Utilization of these ligands in the copper-catalyzed enantioselective conjugate addition of trimethylaluminum to 2-cyclohexenone afforded 3-methylcyclohexanone with up to
Stereocontrol with lithium trimethylzincate toward gibberellin synthesis
Isobe, Minoru,Chiang, Ching-Te,Tsao, Kuo-Wei,Cheng, Chia-Yi,Bruening, Reimar
, p. 2109 - 2113 (2012)
Substrate control in target-oriented synthesis is generally important in establishing the required stereogenic center rather than reagent control. During the course of the total synthesis toward Gibberellin A3 (1), a model compound (21) as the A-ring of 1 was accomplished in five overall steps with an overall yield of 15 %, starting from furfural through conjugate addition of lithium trimethylzincate to oxabicyclo[2.2.1]heptadienedicarboxylic ester (2) as the key step. Relative to more common lithium dimethylcuprate or aluminum reagents, this zincate complex showed a complete selectivity with higher reactivity than with other simple enone compounds. The incoming methyl group was 100 % selective from the ring oxygen side of 2, and the enolate intermediate can be protonated stereoselectivly without the bridge-oxygen-ring opening.
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.
Selective hydrogenation of phenol to cyclohexanone over Pd nanoparticles encaged hollow mesoporous silica catalytic nanoreactors
Li, Kaijie,Wang, Junyou,Yang, Caoping,Zhou, Shenghu
, (2020/12/25)
Pd nanoparticles (NPs) encaged hollow mesoporous silica nanoreactors (Pd?HMSNs) are prepared for hydrogenations of phenol, cresols and chlorophenols to cyclohexanone derivatives. Pd?HMSNs feature ～ 4 nm Pd NPs in ～ 16 nm hollow cavities of ～ 30 nm HMSNs. Such Pd?HMSNs are highly thermally and catalytically stable. At mild reaction conditions, Pd?HMSNs efficiently catalyze hydrogenations of phenol and m-cresol to cyclohexanone derivatives with ≥ 98.3 % selectivity at ≥ 99.0 % conversions. Hydrogenations of o- and m-chlorophenol over Pd?HMSNs give cyclohexanone with ≥ 97.3 % selectivity at 100.0 % conversions, demonstrating a beneficial effect of such HMSNs for consecutive reactions. The confinement of Pd NPs inside hollow cavities of mesoporous nanoreactors greatly promotes collision times of reactant molecules with Pd NPs, resulting in an enhanced catalytic efficiency, while the residence of Pd NPs inside cavities provides a protecting effect for Pd NPs and is beneficial to thermal and catalytic stabilities.
Highly Selective Hydrogenation of Phenols to Cyclohexanone Derivatives Using a Palladium@N-Doped Carbon/SiO2Catalyst
Sheng, Xueru,Wang, Chao,Wang, Wentao
supporting information, p. 2425 - 2431 (2021/11/16)
A new palladium-based heterogeneous material was synthesized by means of immobilization of Pd(OAc)2/1,10-phenanthroline on commercially available SiO2and subsequent pyrolysis at 600 °C for 2 h in air, namely, a Pd@N-doped carbon/SiO2catalyst. The obtained catalyst was studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS) techniques, and was effectively applied in the highly selective hydrogenation of phenols to give the corresponding cyclohexanone derivatives with 93-98% yields at 100 °C under 0.4 MPa H2in EtOH. It was demonstrated that introducing nitrogen could effectively promote the Pd dispersion and enhance the electronic interaction of Pd, both of which facilitate the improvement of the catalytic activity and selectivity. The likely reaction pathway was outlined to elucidate the selective hydrogenation mechanism according to experimental results.
Photoredox-Catalyzed Simultaneous Olefin Hydrogenation and Alcohol Oxidation over Crystalline Porous Polymeric Carbon Nitride
Qiu, Chuntian,Sun, Yangyang,Xu, Yangsen,Zhang, Bing,Zhang, Xu,Yu, Lei,Su, Chenliang
, p. 3344 - 3350 (2021/07/26)
Booming of photocatalytic water splitting technology (PWST) opens a new avenue for the sustainable synthesis of high-value-added hydrogenated and oxidized fine chemicals, in which the design of efficient semiconductors for the in-situ and synergistic utilization of photogenerated redox centers are key roles. Herein, a porous polymeric carbon nitride (PPCN) with a crystalline backbone was constructed for visible light-induced photocatalytic hydrogen generation by photoexcited electrons, followed by in-situ utilization for olefin hydrogenation. Simultaneously, various alcohols were selectively transformed to valuable aldehydes or ketones by photoexcited holes. The porosity of PPCN provided it with a large surface area and a short transfer path for photogenerated carriers from the bulk to the surface, and the crystalline structure facilitated photogenerated charge transfer and separation, thus enhancing the overall photocatalytic performance. High reactivity and selectivity, good functionality tolerance, and broad reaction scope were achieved by this concerted photocatalysis system. The results contribute to the development of highly efficient semiconductor photocatalysts and synergistic redox reaction systems based on PWST for high-value-added fine chemical production.
Synthesis of Chiral Amines via a Bi-Enzymatic Cascade Using an Ene-Reductase and Amine Dehydrogenase
Fossey-Jouenne, Aurélie,Jongkind, Ewald P. J.,Mayol, Ombeline,Paul, Caroline E.,Vergne-Vaxelaire, Carine,Zaparucha, Anne
, (2021/12/23)
Access to chiral amines with more than one stereocentre remains challenging, although an increasing number of methods are emerging. Here we developed a proof-of-concept bi-enzymatic cascade, consisting of an ene reductase and amine dehydrogenase (AmDH), to afford chiral diastereomerically enriched amines in one pot. The asymmetric reduction of unsaturated ketones and aldehydes by ene reductases from the Old Yellow Enzyme family (OYE) was adapted to reaction conditions for the reductive amination by amine dehydrogenases. By studying the substrate profiles of both reported biocatalysts, thirteen unsaturated carbonyl substrates were assayed against the best duo OYE/AmDH. Low (5 %) to high (97 %) conversion rates were obtained with enantiomeric and diastereomeric excess of up to 99 %. We expect our established bi-enzymatic cascade to allow access to chiral amines with both high enantiomeric and diastereomeric excess from varying alkene substrates depending on the combination of enzymes.
Visible-light photocatalytic selective oxidation of C(sp3)-H bonds by anion-cation dual-metal-site nanoscale localized carbon nitride
Duan, Limei,Li, Peihe,Li, Wanfei,Liu, Jinghai,Liu, Ying,Liu, Zhifei,Lu, Ye,Sarina, Sarina,Wang, Jinghui,Wang, Yin,Wang, Yingying,Zhu, Huaiyong
, p. 4429 - 4438 (2021/07/12)
Selective oxidation of C(sp3)-H bonds to carbonyl groups by abstracting H with a photoinduced highly active oxygen radical is an effective method used to give high value products. Here, we report a heterogeneous photocatalytic alkanes C-H bonds oxidation method under the irradiation of visible light (λ= 425 nm) at ambient temperature using an anion-cation dual-metal-site modulated carbon nitride. The optimized cation (C) of Fe3+or Ni2+, with an anion (A) of phosphotungstate (PW123?) constitutes the nanoscale dual-metal-site (DMS). With a Fe-PW12dual-metal-site as a model (FePW), we demonstrate a A-C DMS nanoscale localized carbon nitride (A-C/g-C3N4) exhibiting a highly enhanced photocatalytic activity with a high product yield (86% conversion), selectivity (up to 99%), and a wide functional group tolerance (52 examples). The carbon nitride performs the roles of both the visible light response, and improves the selectivity for the oxidation of C(sp3)-H bonds to carbonyl groups, along with the function of A-C DMS in promoting product yield. Mechanistic studies indicate that this reaction follows a radical pathway catalyzed by a photogenerated electron and hole on A-C/g-C3N4that is mediated by thetBuO˙ andtBuOO˙ radicals. Notably, a 10 g scale reaction was successfully achieved for alkane photocatalytic oxidation to the corresponding product with a good yield (80% conversion), and high selectivity (95%) under natural sunlight at ambient temperature. In addition, this A-C/g-C3N4photocatalyst is highly robust and can be reused at least six times and the activity is maintained.
Hydrodeoxygenation of m-cresol as a depolymerized lignin probe molecule: Synergistic effect of NiCo supported alloys
Gon?alves, Vinicius Ottonio O.,Talon, Walter Henrique S.M.,Kartnaller, Vinicius,Venancio, Fabricio,Cajaiba, Jo?o,Cabioc'h, Thierry,Clacens, Jean-Marc,Richard, Frédéric
, p. 135 - 144 (2021/01/04)
Three bimetallic Ni-Co (Ni:Co ratio 1:3, 1:1 and 3:1) and two monometallic (Ni and Co) nanoparticles supported on Al2O3 were synthesized by incipient wet impregnation and characterized by various technics (N2-physisorption, XRD, H2-TPR, CO-chemisorption and elemental analysis). It was demonstrated by XRD that NiCo alloys nanoparticles were present on bimetallic solids. The catalytic properties of all catalysts were determined for the hydrodeoxygenation of m-cresol at 340 °C under 4 MPa of total pressure. It was demonstrated that NiCo alloy developed better deoxygenation catalytic properties than pure Ni metallic phase, these properties being evaluated both by the total reaction rate (kTOT) and the selectivity into deoxygenation products. Indeed, bimetallic NiCo(3:1)/Al2O3 was 1.2 times more active than Ni/Al2O3 and 8.8 times than Co/Al2O3, deoxygenated products being favored on bimetallic catalysts compared to Ni one. In addition, the kTOT values seems to be related to the amount of CO uptakes, indicating that active sites in HDO were of similar nature than those allowing the adsorption of CO, and could be oxygen vacancies which were promoted in bimetallic Ni-Co particles.
