693-54-9Relevant articles and documents
A novel redox system for the palladium(II)-catalyzed oxidation based on redox of polyanilines
Hirao, Toshikazu,Higuchi, Masayoshi,Hatano, Bunpei,Ikeda, Isao
, p. 5925 - 5928 (1995)
A complex system consisting of palladium(II) acetate and polyaniline derivatives permitted the catalytic Wacker oxidation, indicating that polyanilines serve as a ligand with reversible redox capability under oxygen atmosphere. Substitution on the phenyl ring and protonic acid doping of polyanilines were found to affect the catalytic activity.
Recyclable catalyst reservoir: Oxidation of alcohols mediated by noncovalently supported bis(imidazolium)-tagged 2,2,6,6-tetramethylpiperidine 1-oxyl
Beejapur, Hazi Ahmad,Giacalone, Francesco,Noto, Renato,Franchi, Paola,Lucarini, Marco,Gruttadauria, Michelangelo
, p. 2991 - 2999 (2013)
Bis(imidazolium)-tagged 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) catalysts were adsorbed on different supports such as silica gel, silica gel modified with highly cross-linked polymeric imidazolium networks, and highly cross-linked polymeric imidazolium networks entrapping magnetic particles. These systems provided a convenient tool for the oxidation of both primary and secondary alcohols working as recyclable reservoirs for the bis(imidazolium)-tagged TEMPO catalysts. By using EPR spectroscopy it was demonstrated that the catalyst was released as the corresponding oxoammonium salt in the solution during the recycling step, thus promoting the oxidative process in a homogeneous fashion. After solvent removal, the catalyst was readsorbed on the support allowing an easy recovery and recycle of the catalytic material up to 13 consecutive cycles with no loss in activity. The bis(imidazolium)-tagged TEMPO catalyst could be used in only 1mol% both for the oxidation of benzylic and aliphatic alcohols. The catalytic material was highly recyclable if used on silica or imidazolium-modified silica gel in 10mol% loading. Loading could be scaled down to 1mol% and the catalyst proved to be recyclable up to 8cycles only with imidazolium-modified silica gel. Such a "catalyst-sponge-like" system permits to combine the benefits of homogeneous and heterogeneous catalysis. Catch and release: Why spend money on covalent immobilization or ionic liquids with bulky cations? A bis(imidazolium)-modified 2,2,6,6-tetramethylpiperidine 1-oxyl catalyst can be adsorbed on an imidazolium-modified support, then released in the presence of a proper organic solvent and recaptured at the end of the reaction on removal of the solvent.
Palladium-copper-DMF complexes involved in the oxidation of alkenes
Hosokawa, Takahiro,Nomura, Toshihiro,Murahashi, Shun-Ichi
, p. 387 - 389 (1998)
Treatment of PdCl2(MeCN)2 and CuCl with N,N-dimethylformamide (DMF) under O2 gives polymeric complex [(PdCl2)2CuCl2(DMF)4]n (1) and Pd-Cu heterometallic complex 2 containing O atom derived from molecular oxygen.
V2O5@TiO2 Catalyzed Green and Selective Oxidation of Alcohols, Alkylbenzenes and Styrenes to Carbonyls
Upadhyay, Rahul,Kumar, Shashi,Maurya, Sushil K.
, p. 3594 - 3600 (2021/07/02)
The versatile application of different functional groups such as alcohols (1° and 2°), alkyl arenes, and (aryl)olefins to construct carbon-oxygen bond via oxidation is an area of intense research. Here, we report a reusable heterogeneous V2O5@TiO2 catalyzed selective oxidation of various functionalities utilizing different mild and eco-compatible oxidants under greener reaction conditions. The method was successfully applied for the alcohol oxidation, oxidative scission of styrenes, and benzylic C?H oxidation to their corresponding aldehydes and ketones. The utilization of mild and eco-friendly oxidizing reagents such as K2S2O8, H2O2 (30 % aq.), TBHP (70 % aq.), broad substrate scope, gram-scale synthesis, and catalyst recyclability are notable features of the developed protocol.
Bismuth subnitrate-catalyzed markovnikov-type alkyne hydrations under batch and continuous flow conditions
?tv?s, Sándor B.,Fül?p, Ferenc,Szécsényi, Zsanett
, (2021/05/31)
Bismuth subnitrate is reported herein as a simple and efficient catalyst for the atom-economical synthesis of methyl ketones via Markovnikov-type alkyne hydration. Besides an effective batch process under reasonably mild conditions, a chemically intensified continuous flow protocol was also developed in a packed-bed system. The applicability of the methodologies was demonstrated through hydration of a diverse set of terminal acetylenes. By simply switching the reaction medium from methanol to methanol-d4, valuable trideuteromethyl ketones were also prepared. Due to the ready availability and nontoxicity of the heterogeneous catalyst, which eliminated the need for any special additives and/or harmful reagents, the presented processes display significant advances in terms of practicality and sustainability.
Structural elucidation of a methylenation reagent of esters: Synthesis and reactivity of a dinuclear titanium(iii) methylene complex
Kurogi, Takashi,Kuroki, Kaito,Moritani, Shunsuke,Takai, Kazuhiko
, p. 3509 - 3515 (2021/03/29)
Transmetallation of a zinc methylene complex [ZnI(tmeda)]2(μ-CH2) with a titanium(iii) chloride [TiCl3(tmeda)(thf)] produced a titanium methylene complex. The X-ray diffraction study displayed a dinuclear methylene structure [TiCl(tmeda)]2(μ-CH2)(μ-Cl)2. Treatment of an ester with the titanium methylene complex resulted in methylenation of the ester carbonyl to form a vinyl ether. The titanium methylene complex also reacted with a terminal olefin, resulting in olefin-metathesis and olefin-homologation. Cyclopropanation by methylene transfer from the titanium methylene proceeded by use of a 1,3-diene. The mechanistic study of the cyclopropanation reaction by the density functional theory calculations was also reported.
Tuning Flavin-Based Photocatalytic Systems for Application in the Mild Chemoselective Aerobic Oxidation of Benzylic Substrates
Tolba, Amal Hassan,Vávra, Franti?ek,Chudoba, Josef,Cibulka, Radek
supporting information, p. 1579 - 1585 (2019/12/24)
New flavin-based photocatalytic systems used for chemoselective aerobic visible-light oxidations have been developed by tuning the flavin structure and reaction conditions. 1,3-Dimethyl-7-trifluoromethylalloxazine (2) and 10-butyl-3-methyl-7-trifluoromethylisoalloxazine (3) were shown to mediate the selective oxidation of benzyl alcohols to form aldehydes in the presence of Cs2CO3. Flavin 3 was superior in the oxidation of toluene derivatives to form aldehydes in the presence of trifluoroacetic acid. On the other hand, photooxidations provided by ethylene-bridged quaternary flavinium salt 1 gave the corresponding carboxylic acids. The usefulness of the developed catalytic systems using 1–3 was also demonstrated in the oxidation of secondary benzylic and aliphatic alcohols, and benzylic methylene groups to form the corresponding ketones. The systems have the advantage of a broad substrate scope and metal-free conditions, which distinguish them from the previously reported flavin photooxidation reactions.
Hydration of terminal alkynes catalyzed by cobalt corrole complex
Lai, Jia-Wei,Liu, Zhao-Yang,Chen, Xiao-Yan,Zhang, Hao,Liu, Hai-Yang
supporting information, (2020/10/02)
Cobalt(III) corrole was firstly applied to the hydration of terminal alkynes. The alkyne hydration proceeded in good to excellent yield with 0.03 to 0.3 mol% cobalt corrole catalyst loading. A wide range of substrates were tolerated. Particularly, the reaction can give 90% yield in a gram scale experiment.
MnO2as a terminal oxidant in Wacker oxidation of homoallyl alcohols and terminal olefins
Fernandes, Rodney A.,Ramakrishna, Gujjula V.,Bethi, Venkati
, p. 6115 - 6125 (2020/10/27)
Efficient and mild reaction conditions for Wacker-type oxidation of terminal olefins of less explored homoallyl alcohols to β-hydroxy-methyl ketones have been developed by using a Pd(ii) catalyst and MnO2 as a co-oxidant. The method involves mild reaction conditions and shows good functional group compatibility along with high regio- and chemoselectivity. While our earlier system of PdCl2/CrO3/HCl produced α,β-unsaturated ketones from homoallyl alcohols, the present method provided orthogonally the β-hydroxy-methyl ketones. No overoxidation or elimination of benzylic and/or β-hydroxy groups was observed. The method could be extended to the oxidation of simple terminal olefins as well, to methyl ketones, displaying its versatility. An application to the regioselective synthesis of gingerol is demonstrated.
Selective Visible Light Aerobic Photocatalytic Oxygenation of Alkanes to the Corresponding Carbonyl Compounds
Somekh, Miriam,Khenkin, Alexander M.,Herman, Adi,Neumann, Ronny
, p. 8819 - 8824 (2019/09/30)
The aerobic, selective oxygenation of alkanes via C-H bond activation is an important research challenge. Photocatalysis offers the potential for the introduction of additional concepts for such reactions. Visible light photoactive semiconductors such as bismuth oxyhalides (BiOX, X = Cl and Br) used in this research typically oxidize organic compounds through photocatalyzed formation of strongly oxidizing holes. The reactive oxygen species formed react with organic compounds in one-electron processes, leading to radical intermediates and nonselective oxidation. Such oxidation reactions generally lead to total oxidation. Here, impregnation of BiOX with a polyoxometalate, H5PV2Mo10O40, as a strong electron acceptor changed the reactivity of BiOX, leading to Mars-van Krevelen-type reactivity, that is, photoactivated oxygen donation from BiOX to the organic substrate followed by reoxidation by O2 and catalysis. This conclusion was supported by mechanistic studies involving isotope labeling studies. In this way, ethane was selectively oxidized to acetaldehyde in a flow reactor with a turnover number (24 h) of 415.
