- Scalable, Telescoped Hydrogenolysis-Enzymatic Decarboxylation Process for the Asymmetric Synthesis of (R)-α-Heteroaryl Propionic Acids
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Enantiopure α-aryl propionic acids are useful building blocks for pharmaceutical research and can be accessed enzymatically using arylmalonate decarboxylases (AMDases) from the corresponding malonic acids. However, the intrinsic instability of malonic acids is a major drawback to this approach in which spontaneous decarboxylation can occur, subsequently eroding enantioselectivity and giving rise to racemic products. This was particularly evident for a panel of N-heterocyclic propionic acids that we wished to access using the approach. Herein, we describe a process to overcome the spontaneous decarboxylation problem in which hydrogenolysis of the corresponding dibenzyl malonates was performed in a biphasic toluene-basic aqueous buffer mixture and telescoped into the subsequent AMDase step. This procedure enabled compounds to be accessed in high enantioselectivities and was successfully demonstrated on 120 g with high yield (76%) and ee (98%).
- Blakemore, Caroline A.,France, Scott P.,Samp, Lacey,Nason, Deane M.,Yang, Eddie,Howard, Roger M.,Coffman, Karen J.,Yang, Qingyi,Smith, Aaron C.,Evrard, Edelweiss,Li, Wei,Dai, Linlin,Yang, Lixia,Chen, Zhiguang,Zhang, Qingli,He, Fangyan,Zhang, Jiesen
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supporting information
p. 421 - 426
(2020/11/12)
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- Metal-Organic Framework-Confined Single-Site Base-Metal Catalyst for Chemoselective Hydrodeoxygenation of Carbonyls and Alcohols
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Chemoselective deoxygenation of carbonyls and alcohols using hydrogen by heterogeneous base-metal catalysts is crucial for the sustainable production of fine chemicals and biofuels. We report an aluminum metal-organic framework (DUT-5) node support cobalt(II) hydride, which is a highly chemoselective and recyclable heterogeneous catalyst for deoxygenation of a range of aromatic and aliphatic ketones, aldehydes, and primary and secondary alcohols, including biomass-derived substrates under 1 bar H2. The single-site cobalt catalyst (DUT-5-CoH) was easily prepared by postsynthetic metalation of the secondary building units (SBUs) of DUT-5 with CoCl2 followed by the reaction of NaEt3BH. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy (XANES) indicated the presence of CoII and AlIII centers in DUT-5-CoH and DUT-5-Co after catalysis. The coordination environment of the cobalt center of DUT-5-Co before and after catalysis was established by extended X-ray fine structure spectroscopy (EXAFS) and density functional theory. The kinetic and computational data suggest reversible carbonyl coordination to cobalt preceding the turnover-limiting step, which involves 1,2-insertion of the coordinated carbonyl into the cobalt-hydride bond. The unique coordination environment of the cobalt ion ligated by oxo-nodes within the porous framework and the rate independency on the pressure of H2 allow the deoxygenation reactions chemoselectively under ambient hydrogen pressure.
- Antil, Neha,Kumar, Ajay,Akhtar, Naved,Newar, Rajashree,Begum, Wahida,Manna, Kuntal
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supporting information
p. 9029 - 9039
(2021/06/28)
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- Chemoselective Hydrogenation of Olefins Using a Nanostructured Nickel Catalyst
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The selective hydrogenation of functionalized olefins is of great importance in the chemical and pharmaceutical industry. Here, we report on a nanostructured nickel catalyst that enables the selective hydrogenation of purely aliphatic and functionalized olefins under mild conditions. The earth-abundant metal catalyst allows the selective hydrogenation of sterically protected olefins and further tolerates functional groups such as carbonyls, esters, ethers and nitriles. The characterization of our catalyst revealed the formation of surface oxidized metallic nickel nanoparticles stabilized by a N-doped carbon layer on the active carbon support.
- Klarner, Mara,Bieger, Sandra,Drechsler, Markus,Kempe, Rhett
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supporting information
p. 2157 - 2161
(2021/05/21)
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- Ambient Hydrogenation and Deuteration of Alkenes Using a Nanostructured Ni-Core–Shell Catalyst
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A general protocol for the selective hydrogenation and deuteration of a variety of alkenes is presented. Key to success for these reactions is the use of a specific nickel-graphitic shell-based core–shell-structured catalyst, which is conveniently prepared by impregnation and subsequent calcination of nickel nitrate on carbon at 450 °C under argon. Applying this nanostructured catalyst, both terminal and internal alkenes, which are of industrial and commercial importance, were selectively hydrogenated and deuterated at ambient conditions (room temperature, using 1 bar hydrogen or 1 bar deuterium), giving access to the corresponding alkanes and deuterium-labeled alkanes in good to excellent yields. The synthetic utility and practicability of this Ni-based hydrogenation protocol is demonstrated by gram-scale reactions as well as efficient catalyst recycling experiments.
- Beller, Matthias,Feng, Lu,Gao, Jie,Jackstell, Ralf,Jagadeesh, Rajenahally V.,Liu, Yuefeng,Ma, Rui
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supporting information
p. 18591 - 18598
(2021/06/28)
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- Preparation method of 4-ethylpyridine
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The invention relates to the technical field of organic synthesis, in particular to a preparation method of 4-ethylpyridine. The preparation method of the 4-ethylpyridine comprises the following stepsof: mixing ethyl 4-picolinate with sodium ethoxide, heating to 90 to 110 DEG C, then dropwise adding ethyl acetate, and carrying out claisen condensation reaction, thus obtaining ethyl 3-oxo-3-(4-pyridyl) propionate; mixing the ethyl 3-oxo-3-(4-pyridyl) propionate, dimethyl sulfoxide and water, and carrying out heating treatment, thus obtaining 4-acetylpyridine; cooling after mixing glycol with potassium hydroxide, adding hydrazine hydrate, rising the temperature to 60 to 80 DEG C, then mixing with the 4-acetylpyridine, and carrying out reduction reaction, thus obtaining the 4-ethylpyridine.The 4-ethylpyridine prepared through the preparation method provided by the invention is higher in yield and purity.
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Paragraph 0060; 0068-0069; 0070; 0078-0079; 0080; 0088-0089
(2019/04/10)
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- Rethinking Basic Concepts-Hydrogenation of Alkenes Catalyzed by Bench-Stable Alkyl Mn(I) Complexes
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An efficient additive-free manganese-catalyzed hydrogenation of alkenes to alkanes with molecular hydrogen is described. This reaction is atom economic, implementing an inexpensive, earth-abundant nonprecious metal catalyst. The most efficient precatalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-alkyl bond to yield an acyl intermediate which undergoes rapid hydrogenolysis to form the active 16e Mn(I) hydride catalyst [Mn(dippe)(CO)2(H)]. A range of mono- A nd disubstituted alkenes were efficiently converted into alkanes in good to excellent yields. The hydrogenation of 1-alkenes and 1,1-disubstituted alkenes proceeds at 25 °C, while 1,2-disubstituted alkenes require a reaction temperature of 60 °C. In all cases, a catalyst loading of 2 mol % and a hydrogen pressure of 50 bar were applied. A mechanism based on DFT calculations is presented, which is supported by preliminary experimental studies.
- Weber, Stefan,St?ger, Berthold,Veiros, Luis F.,Kirchner, Karl
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p. 9715 - 9720
(2019/10/14)
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- Disilaruthena- and Ferracyclic Complexes Containing Isocyanide Ligands as Effective Catalysts for Hydrogenation of Unfunctionalized Sterically Hindered Alkenes
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Disilaferra- and disilaruthenacyclic complexes containing mesityl isocyanide as a ligand, 3′ and 4′, were synthesized and characterized by spectroscopy and crystallography. Both 3′ and 4′ showed excellent catalytic activity for the hydrogenation of alkenes. Compared with iron and ruthenium carbonyl analogues, 1′ and 2′, the isocyanide complexes 3′ and 4′ were more robust under the hydrogenation conditions, and were still active even at higher temperatures (~80 °C) under high hydrogen pressure (~20 atm). The iron complex 3′ exhibited the highest catalytic activity toward hydrogenation of mono-, di-, tri-, and tetrasubstituted alkenes among currently reported iron catalysts. Ruthenium complex 4′ catalyzed hydrogenation under very mild conditions, such as room temperature and 1 atm of H2. The remarkably high catalytic activity of 4′ for hydrogenation of unfunctionalized tetrasubstituted alkenes was especially notable, because it was comparable to the activity of iridium complexes reported by Crabtree and Pfaltz, which are catalysts with the highest activity in the literature. DFT calculations suggested two plausible catalytic cycles, both of which involved activation of H2 assisted by the metal-silicon bond through σ-bond metathesis of late transition metals (oxidative hydrogen migration). The linear structure of M C≡N - C (ipso carbon of the mesityl group) played an essential role in the efficient hydrogenation of sterically hindered tetrasubstituted alkenes.
- Sunada, Yusuke,Ogushi, Hajime,Yamamoto, Taiji,Uto, Shoko,Sawano, Mina,Tahara, Atsushi,Tanaka, Hiromasa,Shiota, Yoshihito,Yoshizawa, Kazunari,Nagashima, Hideo
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supporting information
p. 4119 - 4134
(2018/03/29)
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- A Bifunctional Reagent Designed for the Mild, Nucleophilic Functionalization of Pyridines
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Herein is reported the design and application of a reagent for the direct functionalization of pyridines. These reactions occur under mild conditions and exhibit broad functional group tolerance, enabling the late-stage functionalization of drug-like molecules. The reagent can be easily prepared on large scale from inexpensive reagents, and reacts in the title reaction with acetonitrile, sodium chloride, and sodium methanesulfonate as the sole byproducts. Although this Communication focuses primarily on reactions with cyanide as nucleophile, preliminary experiments with other nucleophiles foreshadow the broad reaching synthetic utility of this approach.
- Fier, Patrick S.
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supporting information
p. 9499 - 9502
(2017/07/24)
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- Divalent Silicon-Assisted Activation of Dihydrogen in a Bis(N-heterocyclic silylene)xanthene Nickel(0) Complex for Efficient Catalytic Hydrogenation of Olefins
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The first chelating bis(N-heterocyclic silylene)xanthene ligand [SiII(Xant)SiII] as well as its Ni complexes [SiII(Xant)SiII]Ni(η2-1,3-cod) and [SiII(Xant)SiII]Ni(PMe3)2 were synthesized and fully characterized. Exposing [SiII(Xant)SiII]Ni(η2-1,3-cod) to 1 bar H2 at room temperature quantitatively generated an unexpected dinuclear hydrido Ni complex with a four-membered planar Ni2Si2 core. Exchange of the 1,3-COD ligand by PMe3 led to [SiII(Xant)SiII]Ni(PMe3)2, which could activate H2 reversibly to afford the first SiII-stabilized mononuclear dihydrido Ni complex characterized by multinuclear NMR and single-crystal X-ray diffraction analysis. [SiII(Xant)SiII]Ni(η2-1,3-cod) is a strikingly efficient precatalyst for homogeneous hydrogenation of olefins with a wide substrate scope under 1 bar H2 pressure at room temperature. DFT calculations reveal a novel mode of H2 activation, in which the SiII atoms of the [SiII(Xant)SiII] ligand are involved in the key step of H2 cleavage and hydrogen transfer to the olefin.
- Wang, Yuwen,Kostenko, Arseni,Yao, Shenglai,Driess, Matthias
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supporting information
p. 13499 - 13506
(2017/10/05)
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- Well-Defined Cobalt(I) Dihydrogen Catalyst: Experimental Evidence for a Co(I)/Co(III) Redox Process in Olefin Hydrogenation
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The synthesis of a cobalt dihydrogen CoI-(H2) complex prepared from a CoI-(N2) precursor supported by a monoanionic pincer bis(carbene) ligand, MesCCC (MesCCC = bis(mesityl-benzimidazol-2-ylidene)phenyl), is described. This species is capable of H2/D2 scrambling and hydrogenating alkenes at room temperature. Stoichiometric addition of HCl to the CoI-(N2) cleanly affords the CoIII hydridochloride complex, which, upon the addition of Cp2ZrHCl, evolves hydrogen gas and regenerates the CoI-(N2) complex. Furthermore, the catalytic olefin hydrogenation activity of the CoI species was studied by using multinuclear and parahydrogen (p-H2) induced polarization (PHIP) transfer NMR studies to elucidate catalytically relevant intermediates, as well as to establish the role of the CoI-(H2) in the CoI/CoIII redox cycle.
- Tokmic, Kenan,Markus, Charles R.,Zhu, Lingyang,Fout, Alison R.
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supporting information
p. 11907 - 11913
(2016/10/07)
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- A Concise and Atom-Economical Suzuki-Miyaura Coupling Reaction Using Unactivated Trialkyl- and Triarylboranes with Aryl Halides
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A concise and atom-economical Suzuki-Miyaura coupling of trialkyl- and triarylboranes with aryl halides is described. This new protocol represents the first general, practical method that efficiently utilizes peralkyl and peraryl groups of the unactivated trialkyl- and triarylboranes for the Suzuki-Miyaura coupling reaction.
- Li, Hongmei,Zhong, Yong-Li,Chen, Cheng-Yi,Ferraro, Ashley E.,Wang, Dengjin
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supporting information
p. 3616 - 3619
(2015/07/28)
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- Palladium nanoparticles supported on fibrous-structured silica nanospheres (KCC-1): An efficient and selective catalyst for the transfer hydrogenation of alkenes
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An efficient palladium catalyst supported on fibrous silica nanospheres (KCC-1) has been developed for the hydrogenation of alkenes and α,β-unsaturated carbonyl compounds, providing excellent yields of the corresponding products with remarkable chemoselectivity. Comparison (high-resolution TEM, chemisorption) with analogous mesoporous (MCM-41, SBA-15) silica-supported Pd nanocatalysts prepared under identical conditions, demonstrates the advantage of employing the fibrous KCC-1 morphology versus traditional supports because it ensures superior accessibility of the catalytically active cores along with excellent Pd dispersion at high metal loading. This morphology ultimately leads to higher catalytic activity for the KCC-1-supported nanoparticles. The protocol developed for hydrogenation is advantageous and environmentally benign owing to the use of HCOOH as a source of hydrogen, water as a solvent, and because of efficient catalyst recyclability and durability. The recycled catalyst has been analyzed by XPS spectroscopy and TEM showing only minor changes in the oxidation state of Pd and in the morphology after the reaction, thus confirming the robustness of the catalyst.
- Qureshi, Ziyauddin S.,Sarawade, Pradip B.,Albert, Matthias,D'Elia, Valerio,Hedhili, Mohamed N.,K?hler, Klaus,Basset, Jean-Marie
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p. 635 - 642
(2015/03/05)
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- Palladium nanoparticles encapsulated in magnetically separable polymeric nanoreactors
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A method for immobilization of palladium nanoparticles in magnetically separable polymeric nanocapsules is presented. The method is based on co-encapsulation of palladium nanoparticles stabilized by hyperbranched polyamidoamine (H-PAMAM-C15) modified with palmitoyl groups and hydrophobic magnetite nanoparticles within polyurea nanospheres. The synthesis of these polyurea nanospheres is based on nanoemulsification of chloroform, containing magnetic nanoparticles and palladium acetate, in water using suitable surfactants or dispersants. Then, the chloroform nano-droplets are confined in a polyurea shell formed by interfacial polycondensation between isocyanate and amine monomers. The palladium acetate was reduced with hydrogen to create palladium nanoparticles dispersed in the core of the polyurea nanocapsules. These catalytic polymeric nanoreactors were utilized in hydrogenation of alkenes and alkynes in water. The nanoreactors were easily separated from the reaction mixture via application of external magnetic field. The recyclability of these nanoreactors was examined in hydrogenation of styrene; no significant change was observed in their reactivity for up to four cycles.
- Weiss, Ester,Dutta, Bishnu,Schnell, Yafit,Abu-Reziq, Raed
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p. 3971 - 3977
(2014/03/21)
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- The isolation of [Pd{OC(O)H}(H)(NHC)(PR3)] (NHC = N-heterocyclic carbene) and its role in alkene and alkyne reductions using formic acid
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The [Pd(SIPr)(PCy3)] complex efficiently promotes a tandem process involving dehydrogenation of formic acid and hydrogenation of C-C multiple bonds using H2 formed in situ. The isolation of a key catalytic hydridoformatopalladium species, [Pd{OC(O)H}(H)(IPr)(PCy 3)], is reported. The complex plays a key role in the Pd(0)-mediated formation of hydrogen from formic acid. Mechanistic and computational studies delineate the operational role of the palladium complex in this efficient tandem sequence.
- Broggi, Julie,Jurcik, Vaclav,Songis, Olivier,Poater, Albert,Cavallo, Luigi,Slawin, Alexandra M. Z.,Cazin, Catherine S. J.
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supporting information
p. 4588 - 4591
(2013/05/09)
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- Cooperative effects in catalytic hydrogenation regulated by both the cation and anion of an ionic liquid
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The use of transition-metal nanoparticles/ionic liquid (IL) as a thermoregulated and recyclable catalytic system for hydrogenation has been investigated under mild conditions. The functionalized ionic liquid was composed of poly(ethylene glycol)-functionalized alkylimidazolium as the cation and tris(meta-sulfonatophenyl)phosphine ([P(C6H4-m-SO 3)3]3-) as the anion. Ethyl acetate was chosen as the thermomorphic solvent to avoid the use of toxic organic solvents. Due to a cooperative effect regulated by both the cation and anion of the ionic liquid, the nanocatalysts displayed distinguished temperature-dependent phase behavior and excellent catalytic activity and selectivity, coupled with high stability. In the hydrogenation of α,β-unsaturated aldehydes, the ionic-liquid-stabilized palladium and rhodium nanoparticles exhibited higher selectivity for the hydrogenation of the C=C bonds than commercially available catalysts (Pd/C and Rh/C). We believe that the anion of the ionic liquid, [P(C6H4-m-SO3)3]3-, plays a role in changing the surrounding electronic characteristics of the nanoparticles through its coordination capacity, whereas the poly(ethylene glycol)-functionalized alkylimidazolium cation is responsible for the thermomorphic properties of the nanocatalyst in ethyl acetate. The present catalytic systems can be employed for the hydrogenation of a wide range of substrates bearing different functional groups. The catalysts could be easily separated from the products by thermoregulated phase separation and efficiently recycled ten times without significant changes in their catalytic activity. Copyright
- Zhu, Wenwen,Yu, Yinyin,Yang, Hanmin,Hua, Li,Qiao, Yunxiang,Zhao, Xiuge,Hou, Zhenshan
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p. 2059 - 2066
(2013/03/28)
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- Reduction of alkenes catalyzed by copper nanoparticles supported on diamond nanoparticles
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Copper nanoparticles (Cu NPs) supported on diamond nanoparticles (D NPs) previously purified by Fenton treatment (Cu/D) followed by annealing with hydrogen (Cu/DH) are highly efficient and reusable heterogeneous catalysts for hydrogenation of styrene to ethylbenzene with the minimum productivity value of 30617 cycles. The Royal Society of Chemistry.
- Dhakshinamoorthy, Amarajothi,Navalon, Sergio,Sempere, David,Alvaro, Mercedes,Garcia, Hermenegildo
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supporting information
p. 2359 - 2361
(2013/07/05)
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- New tetraphosphorus ligands for highly linear selective hydroformylation of allyl and vinyl derivatives
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New tetraphosphorus ligands have been developed and applied in the rhodium-catalyzed regioselective hydroformylation of a variety of functionalized allyl and vinyl derivatives. Remarkably high linear selectivity was obtained by these tetraphosphorus ligands. The ligand that bears strong electron-withdrawing 2,4-difluorophenyl groups is the most effective one in affording linear aldehydes. The Rh/tetraphosphorus ligand catalyst is highly effective to produce linear aldehydes from functionalized allyl derivatives with heteroatoms or aromatic groups directly adjacent to the allyl group. For vinyl derivatives, the ligand is highly linear selective for acrylic derivatives, styrene, vinyl pyridine, and vinyl phthalimide. Linear to branch ratios of 26:1 and 10:1 were obtained for the hydroformylation of styrene and allyl cyanide, respectively. New tetraphosphorus ligands have been developed and applied in the rhodium-catalyzed regioselective hydroformylation of a variety of allyl and vinyl olefins (see scheme). Remarkably high linear selectivities were obtained by these ligands. Linear-to-branch ratios of 26:1 and 10:1 were obtained for the hydroformylation of styrene and allyl cyanide, respectively. Copyright
- Cai, Chaoxian,Yu, Shichao,Cao, Bonan,Zhang, Xumu
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experimental part
p. 9992 - 9998
(2012/09/07)
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- The synthesis and applications of a micro-pine-structured nanocatalyst
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Dendritic nanoferrites with a micro-pine morphology have been synthesized for the first time under microwave irradiation conditions without using any reducing or capping reagent; the nanoferrites were then functionalized and coated with Pd metal, which catalyzes various organic transformations. The Royal Society of Chemistry 2008.
- Polshettiwar, Vivek,Nadagouda, Mallikarjuna N.,Varma, Rajender S.
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supporting information; experimental part
p. 6318 - 6320
(2009/04/13)
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- Palladium nanoparticles supported onto ionic carbon nanotubes as robust recyclable catalysts in an ionic liquid
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Palladium nanoparticles have been deposited onto imidazolium bromide-functionalized ionic MWCNTs through hydrogen reduction of Na 2PdCl4 in water without aid of surfactants under extremely mild conditions, and combined with an ionic liquid to create a new recyclable ionic liquid-based catalytic system allowing up to 50 times recycling. The Royal Society of Chemistry.
- Chun, Yu Sung,Shin, Ju Yeon,Song, Choong Eui,Lee, Sang-Gi
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p. 942 - 944
(2008/09/21)
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- Scope, limitations and mechanistic aspects in the selective homogeneous palladium-catalyzed reduction of alkenes under transfer hydrogen conditions
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A new and efficient mild Pd/P(t-Bu)3 catalyst for selective reduction of various alkenes under transfer hydrogen conditions has been developed leading to the corresponding saturated derivatives in chemical yields varying from 65 to 98%. Mechanistic rationale of this reaction has been also demonstrated.
- Brunel, Jean Michel
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p. 3899 - 3906
(2008/02/03)
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- Pd/P(t-Bu)3: A mild catalyst for selective reduction of alkenes under transfer-hydrogenation conditions
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A new and efficient mild Pd/P(t-Bu)3 catalyst for selective reduction of various alkenes under transfer-hydrogenation conditions has been developed leading to the corresponding saturated derivatives in chemical yields varying from 65% to 98%. Georg Thieme Verlag Stuttgart.
- Brunel, Jean Michel
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p. 330 - 332
(2007/10/03)
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- Alkylpyridines transformations over acidic catalysts. An example of radical reactions on ionic surfaces
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4-Methyl-, 4-ethyl-, and 4-isopropylpyridine, ethyl-, and isopropylbenzene transformations were studied over the series of amorphous silica-aluminas. The main reactions of alkylpyridines were the transformations of the alkyl side chain. The crucial role of one-electron donor (radical) centres in the mentioned reactions was evidenced by the physicochemical characterization of the catalyst surfaces, the apparent correlation of activity vs. active centres concentration, and the dependence of product composition upon reaction conditions.
- Kijenski,Malinowski,Kowalczyk,Osawaru
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p. 719 - 736
(2007/10/03)
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- Inhibitors of cell proliferation, angiogenesis, fertility, and muscle contraction
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The invention concerns inhibitors of cell proliferation, angiogenesis, fertility, and muscle contraction, characterized by formula I wherein, X, Y and Z independently represent C or N; ------ is an optional double bond; n is 0 or 1; R1, R2, and R4 independently represent hydrogen, a chemical bond, C1-10 alkyl; C2-10 alkenyl; C2-10 alkinyl; aryl; aryl-C1-10 alkyl; C3-10 heterocyclyl; C5-10 heteroaryl; halo, CF3; NO2; NHC(O)R*, OR, said alkyl, alkenyl, alkinyl, aryl, arylalkyl, heterocyclyl, or heteroaryl being optionally substituted; R3, R5, and R6 independently represent hydrogen, C1-10alkyl; C2-10 alkenyl; C2-10 alkinyl; aryl; aryl-C1-10alkyl; C3-10 heterocyclyl; C5-10 heteroaryl; halo, CF3; NO2; NHC(O)R*, OR, said alkyl, alkenyl, alkinyl, aryl, heterocyclyl, or heteroaryl being optionally substituted; or R5 and R6 together form a 5- or 6-member aryl, heterocyclyl or heteroaryl group; R is hydrogen or C1-6 alkyl; R* is hydrogen, or C1-6 alkyl, or OH, wherein the optional substituents are preferably selected from the group of one to three OH, C1-6 alkyl, halo, NO2, C1-6 alkoxy, and CF3, or a pharmaceutically acceptable salt thereof.
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- Rhodium-catalyzed hydroborations of allylamine and allylimines
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The in situ rhodium-catalyzed addition of catecholborane (HBcat, cat = 1,2-O2C6H4) and pinacolborane (HBpin, pin = 1,2-O2C2Me4) to allylamine, allylimine, 2- and 4-vinylpyridines, and a thienyl imine has been examined using multinuclear NMR spectroscopy. Although reactions of allylamine (H2NCH2CH=CH2) and HBcat gave complex product distributions arising from competing dehydrogenative borylation pathways, addition of HBpin to allylamine using a rhodium catalyst afforded only products arising from hydroboration (RN(Bpin)CH2CH2CH2Bpin, where R = H, Bpin) and hydrogenation (RN(Bpin)CH2CH2CH3). Hydroboration of allylimines (RHC=NCH2CH=CH2, R = Ar) with HBcat occurs initially at the more reactive imine functionality to give unsaturated borylamines (RCH2N(Bcat)CH2CH=CH2). Further reaction with HBcat gives varying amounts of hydroboration products RCH2N(Bcat)CH2CH2CH2Bcat and RCH2N(Bcat)CH2CH(Bcat)CH3 as well as the diboration product RCH2N(Bcat)CH2CH2CH(Bcat)2, depending on the choice of catalyst. Reactions with related unsaturated pyridine derivatives are complicated by extensive degradation, which can be avoided by coordination of the pyridine nitrogen to a Lewis acid. The first examples of metal-catalyzed hydroboration of imines using HBpin are also reported.
- Vogels, Christopher M.,O'Connor, Paul E.,Phillips, Trevor E.,Watson, Keith J.,Shaver, Michael P.,Hayes, Paul G.,Westcott, Stephen A.
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p. 1898 - 1905
(2007/10/03)
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- Chemoselectivity in the rhodium-catalyzed hydroformylation of 4-vinylpyridine: Crucial role of phosphine ligand in promoting carbonylation instead of hydrogenation
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Hydroformylation of 4-vinylpyridine (4VP) in benzene with Rh4(CO)12/PMe2Ph or Rh4CO12 as catalytic precursor shows completely different chemoselectivity, carbonylation product (branched aldehyde) largely prevailing with the first catalyst, hydrogenation product 4-ethylpyridine (4EP) with the second one. Different phosphines and P/Rh ratios were also used, and a comparison with 3-vinylpyridine (3VP) under the same experimental conditions was made too. In all the experiments 3VP exclusively gives aldehidic products. In the case of 4VP, hydrogenation prevails on carbonylation at low P/Rh ratio (0.5), while for higher values more than 80% of carbonylation product is obtained. The strong electron-donor phosphine ligand changes the polarization of the carbon-rhodium bond making this carbon suitable for the migratory insertion process and hence determining the acyl-metal intermediate formation precursor of the aldehyde.
- Caiazzo, Aldo,Settambolo, Roberta,Pontorno, Lorenzo,Lazzaroni, Raffaello
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p. 298 - 303
(2007/10/03)
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- Process for the preparation of fluorinated heterocyclic compounds
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A method of fluorinating a heterocyclic organic compound comprises the step of reacting a heterocyclic compound with elemental fluorine in the presence of another halogen. The reaction may be conducted in the presence of a base.
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- Reduced and quaternized psoralens as photo-activated therapeutics
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The invention features phototherapeutic compositions comprising Type 1, Type 2, or Type 3 psoralens and methods of using such compounds for treatment of proliferative diseases of skin, blood and bone marrow.
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- POTENTIOMETRIC STUDIES ON THE REACTION OF PICRIC ACID WITH SOME AROMATIC AMINES IN METHYL ISOBUTYL KETONE
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The reaction between picric acid and some aniline and pyridine derivatives has been investigated in methyl isobutyl ketone by the potentiometric method.Overall picrate formation constants KBHA, ammonium cationic acid dissociation constants KBH+ and apparent ion-pair formation Ki* and dissociation Kd* constants have been determined.
- Smagowski, Henryk,Bartnicka, Halina
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p. 201 - 209
(2007/10/02)
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- Alkylation of Pyridine in Free Radical Chain Reactions Utilizing Alkylmercurials
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Pyridines or N,N,N',N'-tetramethyl-p-phenylenediamine will undergo a photostimulated free radical chain reaction with alkylmercury halides or carboxylates, yielding ring alkylated substitution products.Alkene mercuration products (R1CH(Y)CH(R2)HgX with Y=HO, RO, CH3CONH; X=Cl, CH3CO2, CF3CO2) can be used without isolation for the alkylation reaction
- Russell, Glen A.,Guo, Deliang,Khanna, Rajive K.
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p. 3423 - 3425
(2007/10/02)
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- Magnesiate Ions in Solutions and Solids Prepared from Dialkylmagnesium Compounds and Cryptands
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Addition of 2,1,1-cryptand to diethylmagnesium solutions greatly speeds reactions with pyridine and leads to formation of significant amounts of a 1,4- as well as a 1,2-addition product, observations attributed to formation of magnesiate species.In crystalline +(2,2,1-cryptand)>2Et6Mg22-, the magnesiums of the dianion are identical and have essentially a tetrahedral bonding geometry.They share two bridging ethyl groups.The magnesium of the cation is bonded to five of the heteroatoms of the cryptand and to the ethyl group.In crystalline NpMg+(2,1,1-cryptand)Np3Mg-, the magnesium of he anion has a trigonal planar bonding geometry.The coordination geometry of the magnesium of the cation is essentially that of a pentagonal bipyramid with bonds to all six of the heteroatoms of the cryptand and a bond to the neopentyl group.The 1H NMR spectrum of a benzene solution of this solid is consistent with the presence of the same ions in the solution.
- Squiller, Edward P.,Whittle, Robert R.,Richey, Herman G.
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p. 432 - 435
(2007/10/02)
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- REACTIONS OF DIETHYLMAGNESIUM - ETHYLLITHIUM SOLUTIONS WITH PYRIDINE
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In contrast to the reactions of pyridine with diethylmagnesium or ethyllithium alone, which lead to 1,2-addition, reactions with diethylmagnesium-ethyllithium solutions lead to significant amounts of 1,4-addition; magnesium ate species are proposed to responsible.
- Richey, Herman G.,Farkas, Julius
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p. 275 - 278
(2007/10/02)
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- NUCLEOPHILIC ADDITION VERSUS METALATION OF 4- AND 2-METHYLPYRIDINE STUDIED BY MULTINUCLEAR MAGNETIC RESONANCE SPECTROSCOPY
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Interaction of 4-methylpyridine with n-butyl-lithium in THF affords a 67:33 mixture of the 1,2-nucleophilic addition product and the laterally metalated derivative of the heterocycle, respectively, as shown by 13C and 15N n.m.r. spectroscopy.While mixtures were also obtained from 4-methylpyridine and methyl- or t-butyl-lithium, only metalation was realized with the lithium salts of di-isopropylamine and 2,2,6,6-tetramethylpiperidine.A regular trend was noted with other 4-alkylpyridines and n-butyl-lithium culminating in exclusive 1,2-addition on 4-n-butylpyridine.The 13C n.m.r. spectrum from 2-methyl-pyridine and n-butyl-lithium also showed the presence of both addition and metalation derivatives; however, the former material was present only to the extent of 3 percent.
- Mansour, Tarek S.,Wong, Tuck C.,Kaiser, Edwin M.
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p. 2045 - 2048
(2007/10/02)
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- Catalytic Reactions of Pyridines. V. Alkylation of α-, β-, and γ-Picolines with Alcohols catalyzed by Ammonium Halides
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A new method was found for the homogeneous liquid-phase alkylation of α-, β-, and γ-picolines with either methanol or ethanol.Addition of a catalytic amount of an ammonium halide to a mixture of a picoline and an alcohol resulted in a great increase in the yields of both side-chain and α-alkylated derivatives of the starting picoline when the reaction was carried out at 320-335 deg C in an atmosphere of nitrogen.The higher the reaction temperature, the greater the yields of side-chain alkylated derivatives became.In practice, this alkylation gave 2-ethylpyridine, and 2,6-lutidine from α-picoline with methanol, 3-ethylpyridine and 2,5-lutidine from β-picoline from methanol, 4-ethylpyridine and 2,4-lutidine from γ-picoline with methanol, 2-propylpyridine and 2-ethyl-6-methylpyridine from α-picoline with ethanol, 2-ethyl-5-methylpyridine from β-picoline with ethanol, and 4-propylpyridine and 2-ethyl-4-methylpyridine from γ-picoline with ethanol.Keywords-alkylation; catalyst; ammonium halide; α-picoline; β-picoline; γ-picoline; ethylpyridine; propylpyridine; methanol; ethanol
- Kashiwagi, Hiroshi,Enomoto, Saburo
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p. 2213 - 2218
(2007/10/02)
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- Catalytic Reactions of Pyridines. IV. Heterogeneous Vapor-phase Side-chain Alkylation of Pyridines with Alcohols over Na+, K+, Rb+, and Cs+ Exchanged Zeolites
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The heterogeneous vapor-phase alkylation of pyridine with methanol over Na+, K+, Rb+, or Cs+ exchanged X- or Y-type zeolite in an atmophere of nitrogen resulted in the formation of 2- and 4-ethylpyridines and 2- and 4-vinylpyridines together with picolines and lutidines.Next, the alkylation of α-, β-, and γ-picolines with methanol was studied over alkali cation exchanged zeolites and was found to produce mainly the side-chain methylated derivatives: ethylpyridines and vinylpyridines.However, considerable amounts of ring-alkylated derivatives (lutidines) were formed simultaneously.In general, the catalytic activity became observable under reaction conditions involving both a high temperature and a small flow rate of carrier gas (N2).The yields of ethylpyridines were highest when the CsY catalyst was used at 450 deg C, whereas the yields of vinylpyridines were highest when the CsX catalyst was used at 425 deg C.This catalytic side-chain alkylation over alkali cation exchanged zeolites was successfully applied to a variety of picolines, lutidines, and ethylpyridines with either methanol or ethanol.
- Kashiwagi, Hiroshi,Enomoto, Saburo
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p. 404 - 411
(2007/10/02)
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- Photochemical Substitution Reactions of 4-Pyridinecarbonitrile with Aliphatic Alcohols in Neutral and Acidified Medium
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Chemical evidence is given that the title photo-reactions proceed via hydrogen abstraction by the photoexcited base from the alcohol in neutral medium and via electron-transfer process between the photo-excited base and the alcohol in hydrochloric acid acidified medium.
- Caronna, Tullio,Clerici, Angelo,Coggiola, Dianella,Morrocchi, Sergio
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p. 1421 - 1423
(2007/10/02)
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- Synthetic Applications of N-N Linked Heterocycles. Part 13. N-(2,5-Dimethylpyrrol-1-yl)pyridinium Salts in the Synthesis of 4-Alkyl and 4-Aryl-pyridines via Regiospecific Attack of Grignard Reagents and Organolithium Compounds.
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The reaction between N-(2,5-dimethylpyrrol-1-yl)pyridinium salts and alkyl- or aryl-Grignard reagents, or organolithium compounds, gives regiospecifically 1,4-dihydro-intermediates.These may be isolated and decomposed under free-radical conditions to give moderate to good yields of 4-alkyl- and 4-aryl-pyridines.Results are compared with those obtained from a related reaction sequence involving N-(2,6-dimethyl-4-oxopyridin-1-yl)pyridinium salts.
- Katritzky, Alan R.,Beltrami, Hector,Sammes, Michael P.
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p. 1684 - 1696
(2007/10/02)
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- Synthetic Applications of N-N Linked Heterocycles. Part 7. The Preparation of 4-Alkyl- and 4-Aryl-pyridines by Regiospecific Attack of Grignard Reagents γ to Quaternary Nitrogen in N-(2,6-Dimethyl-4-oxopyridin-1-yl)pyridinium Salts
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N-(2,6-Dimethyl-4-oxopyridin-1-yl)pyridinium salts (4), new reagents for the regiospecific synthesis of 4-substituted pyridines, give moderate to high yields of 4-alkyl- and 4-aryl-pyridines (8) - (10) on reaction with Grignard reagents.The scope and limitations on the reaction, which proceeds via 1,4-dihydro-intermediates (5) - (7), are explored.No 2-substituted pyridines were detected.Some reactions with organolithium compounds are also described.
- Katritzky, Alan R.,Beltrami, Hector,Sammes, Michael P.
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p. 2480 - 2484
(2007/10/02)
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