104-51-8Relevant articles and documents
Synthesis of insoluble polystyrene-supported flavins and their catalysis in aerobic reduction of olefins
Arakawa, Yukihiro,Kawachi, Risa,Tezuka, Yoshihiko,Minagawa, Keiji,Imada, Yasushi
, p. 1706 - 1713 (2017)
2′,4′-p-Vinylbenzylideneriboflavin (2′,4′-PVBRFl) was prepared as a flavin-containing monomer and copolymerized with divinylbenzene and styrene or its p-substituted derivatives such as 4-acetoxystyrene, 4-vinylbenzyl alcohol, and 4-vinylbenzoic acid to give the corresponding non-functionalized and functionalized PS-DVB-supported flavins PS(H)-DVB-Fl, PS(OAc)-DVB-Fl, PS(CH2OH)-DVB-Fl, and PS(COOH)-DVB-Fl, respectively. PS(OH)-DVB-Fl was also prepared by hydrolysis of PS(OAc)-DVB-Fl under basic conditions. These novel flavin-containing insoluble polymers exhibited characteristic fluorescence in solid state, except PS(OH)-DVB-Fl, and different catalytic activities in aerobic reduction of olefins by in situ generated diimide from hydrazine depending on their pendant functional group. For example, PS(H)-DVB-Fl was found to be particularly effective for neutral hydrophobic substrates, which could be readily recovered by a simple filtration and reused more than 10 times without loss in catalytic activity. On the other hand, PS(OH)-DVB-Fl and PS(COOH)-DVB-Fl proved to be highly active for phenolic substrates known to be less reactive in the reaction with conventional non-supported flavin catalysts.
Improved preparation of secondary zinc iodides by 1,2-migration of sp3 carbenoids
Shibli,Varghese,Knochel,Marek
, p. 818 - 820 (2001)
R2Zn in the presence of NMP or LiBr promotes the intramolecular rearrangement of 1,1-diiodoalkanes via the formation of sp3 secondary zinc carbenoid.
Alkene Hydrogenations by Soluble Iron Nanocluster Catalysts
Gieshoff, Tim N.,Chakraborty, Uttam,Villa, Matteo,Jacobi von Wangelin, Axel
, p. 3585 - 3589 (2017)
The replacement of noble metal technologies and the realization of new reactivities with earth-abundant metals is at the heart of sustainable synthesis. Alkene hydrogenations have so far been most effectively performed by noble metal catalysts. This study reports an iron-catalyzed hydrogenation protocol for tri- and tetra-substituted alkenes of unprecedented activity and scope under mild conditions (1–4 bar H2, 20 °C). Instructive snapshots at the interface of homogeneous and heterogeneous iron catalysis were recorded by the isolation of novel Fe nanocluster architectures that act as catalyst reservoirs and soluble seeds of particle growth.
Efficient and rapid C-Si bond cleavage in supercritical water
Itami, Kenichiro,Terakawa, Koji,Yoshida, Jun-ichi,Kajimoto, Okitsugu
, p. 6058 - 6059 (2003)
Arylsilanes, alkenylsilanes, allylic silanes, and alkylsilanes were found to undergo extremely facile and rapid C-Si bond cleavage in supercritical water. The rapid C-Si bond cleavage occurred even with robust unactivated tetraalkylsilanes. The control experiments revealed the dramatic difference between supercritical and subcritical conditions and that between supercritical water and supercritical methanol, attesting to a unique reactivity of supercritical water in C-Si bond cleavage. Copyright
Scope and Limitations of the Palladium-Catalyzed Cross-Coupling Reaction of in Situ Generated Organoboranes with Aryl and Vinyl Halides
Maddaford, Shawn P.,Keay, Brian A.
, p. 6501 - 6503 (1994)
The in situ palladium(0)-catalyzed Suzuki reaction is shown to be an efficient method for the cross-coupling of aryl-, furyl-, primary, and benzylic boranes with aryl or vinyl bromides and iodides without the isolation of the organoboronic acid or the addition of any external base.
Alkylation of alkyl aromatic hydrocarbons over metal oxide-alkali metal superbasic catalysts
Kijenski,Radomski,Fedorynska
, p. 407 - 425 (2001)
The alkylation of toluene, ethylbenzene, cumene, and o-, m-, and p-xylenes with ethylene, propylene, and 1,2-diphenylethylene was studied over superbasic MgO-K and γ-Al2O3-K catalysts and over model systems of the electron donor acceptor complex type. The ethylation and propylation of alkylbenzenes indicated that the donor power and the concentration of the one-electron donor centers were not the only factors, which determined the activity (depicted by the initial reaction rate, turnover number, or alkylbenzene conversion) and selectivity of the catalytic system. In the series of reactions, a higher total conversion of alkyl aromatic hydrocarbons to their ethylation or propylation products was achieved over γ-Al2O3-K systems. The reaction chemoselectivity (mono- or difunctionalization of alkylbenzenes) depended on the nature of the alkyl aromatic reactant and alkylating alkene, on the reaction temperature, and on the used catalyst.
Divergent Reactivity of Stannane and Silane in the Trifluoromethylation of PdII: Cyclic Transition State versus Difluorocarbene Release
Pu, Maoping,Sanhueza, Italo A.,Senol, Erdem,Schoenebeck, Franziska
, p. 15081 - 15085 (2018)
The transmetalation is a key elementary step in cross-coupling reactions. Yet, the precise nature of its mechanism and transition state geometry are frequently elusive. This report discloses our study of the transmetalation of [PdII]-F complexes with the silane- and stannane-based trifluoromethylation agents, R3SiCF3 and R3SnCF3. A divergent reactivity was uncovered, with the stannane showing selective R-group transfer, and the silane selective CF3-group transfer. Using a combined experimental and computational approach, we uncovered a hitherto unrecognized transmetalation mechanism with the widely employed R3SiCF3 reagent, explaining its unique activity in metal-catalyzed trifluoromethylations. While the stannane reacts via a cyclic, 4-membered transition state, the silane undergoes a fundamentally different pathway and releases a difluorocarbene in the transmetalation event. Molecular dynamics studies clearly reinforced the liberation of a free CF2 carbene, which reacts with [PdII]-F to ultimately generate [PdII]-CF3.
Cross-coupling in a flow microreactor: Space integration of lithiation and murahashi coupling
Nagaki, Aiichiro,Kenmoku, Akira,Moriwaki, Yuya,Hayashi, Atsushi,Yoshida, Jun-Ichi
, p. 7543 - 7547 (2010)
Going with the flow: The use of palladium catalysts bearing a carbene ligand resulted in a faster Murahashi coupling, and enabled its integration with the Br-Li exchange of ArBr with Bu-Li in a microreactor (see picture). This system allows the cross-coupling of two different arylbromides within a minute without necessitating low temperatures (-78°C).
Photoinduced, Copper-Catalyzed Alkylation of Amines: A Mechanistic Study of the Cross-Coupling of Carbazole with Alkyl Bromides
Ahn, Jun Myun,Ratani, Tanvi S.,Hannoun, Kareem I.,Fu, Gregory C.,Peters, Jonas C.
, p. 12716 - 12723 (2017)
We have recently reported that a variety of couplings of nitrogen, sulfur, oxygen, and carbon nucleophiles with organic halides can be achieved under mild conditions (-40 to 30 °C) through the use of light and a copper catalyst. Insight into the various mechanisms by which these reactions proceed may enhance our understanding of chemical reactivity and facilitate the development of new methods. In this report, we apply an array of tools (EPR, NMR, transient absorption, and UV-vis spectroscopy; ESI-MS; X-ray crystallography; DFT calculations; reactivity, stereochemical, and product studies) to investigate the photoinduced, copper-catalyzed coupling of carbazole with alkyl bromides. Our observations are consistent with pathways wherein both an excited state of the copper(I) carbazolide complex ([CuI(carb)2]-) and an excited state of the nucleophile (Li(carb)) can serve as photoreductants of the alkyl bromide. The catalytically dominant pathway proceeds from the excited state of Li(carb), generating a carbazyl radical and an alkyl radical. The cross-coupling of these radicals is catalyzed by copper via an out-of-cage mechanism in which [CuI(carb)2]- and [CuII(carb)3]- (carb = carbazolide), both of which have been identified under coupling conditions, are key intermediates, and [CuII(carb)3]- serves as the persistent radical that is responsible for predominant cross-coupling. This study underscores the versatility of copper(II) complexes in engaging with radical intermediates that are generated by disparate pathways, en route to targeted bond constructions.
Solventless Suzuki coupling reactions on palladium-doped potassium fluoride alumina
Kabalka, George W.,Wang, Lei,Pagni, Richard M.,Hair, C. Maxwell,Namboodiri, Vasudevan
, p. 217 - 222 (2003)
A solventless Suzuki coupling reaction has been developed which utilizes a commercially available potassium fluoride alumina mixture and palladium powder. The new reaction is convenient, environmentally friendly, and generates good yields of the coupled products. Aryl iodides react faster than the bromides or chlorides; aryl groups are also more reactive than alkenyl groups, which react faster than alkyl groups. The use of microwave irradiation accelerates the reaction, decreasing reaction times from hours to minutes. The palladium powder catalyst can be recycled using a simple filtration and washing sequence without loss of catalytic activity.
