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All total 147 Articles be found
All total 147 Articles be foundHighly efficient Au hollow nanosphere catalyzed chemo-selective oxidation of alcohols
Sasidharan, Manickam,Anandhakumar, Sundaramurthy,Bhanja, Piyali,Bhaumik, Asim
, p. 87 - 94 (2016)
Micelles of poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-PVP-PEO) with core-shell-corona structures have been used as a scaffold for the fabrication of gold (Au) hollow nanospheres of particle size 26 ± 2 nm using HAuCl4 and NaBH4 as metal precursor and reducing agent, respectively. The PS core acts as a template for hollow void, the PVP shell serves as reaction sites for inorganic precursors, and PEO corona stabilizes the composite particles. Under acidic conditions, the PVP shell domain becomes positively charged pyridinum-species that electrostatically interacts with negatively charged AuCl4- ions. On reduction of these composite particles and subsequent solvent extraction leads to the formation of Au hollow nanospheres. Various analytical tools such as powder X-ray diffraction (XRD), transmission electron microscope (TEM), thermogravimetric analyses (TG/DTA), dynamic light scattering of (DLS) have been employed to characterize the polymeric micelles and hollow nanoparticles. The TEM and XRD studies confirmed the formation of highly crystalline Au hollow nanospheres. The Au hollow nanosphere/H2O2 system efficiently catalyzes the chemoselective oxidation of allylic-type unsaturated alcohols into aldehydes and ketones under mild liquid-phase conditions. The versatility of present catalytic system for the oxidation of other substrates like aliphatic-, acylic-, aromatic-, and heteroaromatic alcohols to their respective keto compounds has also been reported.
Highly efficient dehydrogenation of secondary alcohols catalyzed by iridium-CNP complexes
Wang, Dawei,Zhao, Keyan,Yang, Shuyan,Ding, Yuqiang
, p. 2016 - 2020 (2014)
A new highly practical method is presented for dehydrogenation of secondary alcohols to the corresponding ketones catalyzed by the iridium-CNP complexes. The reactions are compatible with substrates bearing diverse functional groups and proceed efficiently under mild conditions.
Aerobic oxidation of alcohols at room temperature and atmospheric conditions catalyzed by reusable gold nanoclusters stabilized by the benzene rings of polystyrene derivatives
Miyamura, Hiroyuki,Matsubara, Ryosuke,Miyazaki, Yoji,Kobayashi, Shu
, p. 4151 - 4154 (2007)
(Chemical Equation Presented) Lock up your gold: Polymer-incarcerated gold nanoclusters (PI Au) were synthesized by microencapsulation of gold nanoclusters and cross-linking using a copolymer based on polystyrene (see TEM image). The nanoclusters could be used to catalyze the aerobic oxidation of alcohols to aldehydes and ketones under atmospheric conditions at room temperature, and additionally could be reused with little loss of activity.
Direct conversion of heteroaromatic esters to methyl ketones with trimethylaluminum: Nonsymmetrically disubstituted 1,2,4,5-tetrazines
Girardot, Marc,Nomak, Rana,Snyder, John K.
, p. 10063 - 10068 (1998)
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Studies on pyrazines; 38: Acylation of bromopyrazines and 2-bromopyridine via copper-cocatalytic stille reaction
Sato,Narita
, p. 1551 - 1555 (2001)
Synthesis of acetylpyrazines 3 and propionylpyrazines 5 was achieved by copper-cocatalytic Stille reaction of bromopyrazines 1 with tributyl(1-ethoxyalkenyl)tin and then acidic hydrolysis. The optimal reaction conditions involve the combination of 15 molp
Methoxy(2-pyridyl)ketene
Andersen, Heidi Gade,Bednarek, Pawel,Wentrup, Curt
, p. 519 - 524 (2003)
The matrix photolysis of 3-methoxy-carbonyl-1,2,3-triazolopyridine was reported to yield methoxy(2-pyridyl)ketene. Photolysis of the triazolopyridines was found to be a less efficient method of producing the 2-pyridyl-ketenes. The results showed that a different ketene was formed by photolysis, but flash vacuum thermolysis (FVT) afforded the desired methoxy(2-pyridyl)ketene.
4-CH3CONH-TEMPO/Peracetic Acid System for a Shortened Electron-Transfer-Cycle-Controlled Oxidation of Secondary Alcohols
Zhang, Shufang,Miao, Chengxia,Xia, Chungu,Sun, Wei
, p. 1865 - 1870 (2015)
We have developed a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) derivative catalyzed oxidation of secondary alcohols with peracetic acid as the oxidant, which was generated from H2O2 and acetic acid catalyzed by strongly acidic resins. The oxidation of alcohols proceeded well through a shortened electron-transfer cycle under metal-free conditions, avoiding the use of any other electron-transfer mediators such as halides. In addition, we demonstrated that the present system exhibited excellent efficiency under mild conditions for the oxidation of aromatic, aliphatic, and allylic secondary alcohols. Shortcut to ketones: The 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-derivative-catalyzed oxidation of secondary alcohols employing peracetic acid generated from H2O2 and acetic acid with strongly acidic resins proceeds through a shortened electron-transfer cycle without halide additives. The system not only exhibits excellent efficiency at room temperature but also has a wide substrate scope.
Silver nanoparticles immobilized onto poly(4-vinylpyridine)-functionalized magnetic nanoparticles: A robust magnetically recyclable catalyst for oxidant-free alcohol dehydrogenation
Bayat, Ahmad,Shakourian-Fard, Mehdi,Talebloo, Nazanin,Hashemi, Mohammed Mahmoodi
, (2018)
A heterogeneous and recyclable catalyst with a high loading of silver nanoparticles was synthesized via the silver nanoparticles being supported onto the surface of magnetic nanoparticles coated with poly(4-vinylpyridine). The synthesized catalyst was used in the dehydrogenation of alcohols to corresponding carbonyl compounds. A broad diversity of alcohols was converted into their corresponding carbonyl compounds in excellent yields. The catalyst was easily recovered by applying an external magnetic field and reused for seven reaction cycles without considerable loss of activity. The catalyst was fully characterized using various techniques.
Hydration of Alkynes to Ketones with an Efficient and Practical Polyoxomolybdate-based Cobalt Catalyst
Xie, Ya,Wang, Jingjing,Wang, Yunyun,Han, Sheng,Yu, Han
, p. 4985 - 4989 (2021/10/12)
Hydration of alkynes to ketones is one of the most atom economical and universal methods for the synthesis of carbonyl compounds. However, the basic reaction usually requires organic ligand catalysts or harsh reaction conditions to insert oxygen into the C≡C bond. Here, we report an inorganic ligand supported cobalt (III) catalyst, (NH4)3[CoMo6O18(OH)6], which is supported by a central cobalt (III) mononucleus and a ring-shaped pure inorganic ligand composed of six MoVIO6 octahedrons to avoid the disadvantages of expensive and unrecyclable organic ligand catalysts or noble metal catalysts. Under mild conditions, the cobalt (III) catalyst can be used for the hydration of alkynes to ketones. The catalyst is non-toxic, green, and environment friendly. The catalyst can be recycled at least six times with high activity. According to control experiments, a reasonable mechanism is provided.
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.
