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All total 64 Articles be foundDeoxygenation of aldehydes and ketones using dichloro bis(1,4- diazabicyclo[2.2.2]octane)(tetrahydroborato) zirconium(IV)
Alinezhad, Heshmatollah,Tajbakhsh, Mahmood,Salehian, Fatemeh
, p. 170 - 172 (2005)
Saturated aldehydes and ketones are converted via their p-toluenesulfonyl hydrazones to the corresponding alkanes using dichloro bis(1,4-diazabicyclo[2.2. 2]octane)(tetrahydroborato) zirconium(IV) (ZrBDC). The reactions were performed in DMF-sulfolane at 110 °C and gave the corresponding alkanes in high yields. Regioselectivity in the reduction of α,β-unsaturated carbonyl groups was also observed.
Photoinduced Alkoxylation of 2-Vinylpyridinium Ion
Ishida, Akito,Uesugi, Tatsumi,Takamuku, Setsuo
, p. 1580 - 1582 (1993)
Photoirradiation of 2-vinylpyridine in acidic methanol afforded methyl 2-(2-pyridyl)ethylether in a high yield.Reactions in acetic ethanol and 2-propanol also provided the corresponding alkoxyl derivatives along with a considerable amount of 2-ethylpyridine.It was suggested that photoinduced intramolecular charge-shift from the pyridinium ion moiety into the vinyl group initiates the regioselective nucleophilic addition of alcohol.
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Bergstrom,McAllister
, p. 2845,2848 (1930)
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Magnesiate Ions in Solutions and Solids Prepared from Dialkylmagnesium Compounds and Cryptands
Squiller, Edward P.,Whittle, Robert R.,Richey, Herman G.
, p. 432 - 435 (1985)
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.
Electroreductive coupling of vinylpyridines and vinylquinolines: Radical anion-substrate cycloaddition?
Janssen, Robert G.
, p. 539 - 540 (1998)
Cathodic reduction of 2- and 4-vinylpyridine and of 2-vinylquinoline gives trans-1,12-di(heteroaryl)cyclobutanes as major products; they arise via radical anion-substrate cycloaddition.
One-pot o-nitrobenzenesulfonylhydrazide (NBSH) formation-diimide alkene reduction protocol
Marsh, Barrie J.,Carbery, David R.
, p. 3186 - 3188 (2009)
A one-pot protocol for the formation of 2-nitrobenzenesulfonylhydrazide (NBSH) from commercial reagents and subsequent alkene reduction is presented. The transformation is operationally simple and generally efficient for effecting diimide alkene reductions. A range of 16 substrates have been reduced, highlighting the unique chemoselectivity of diimide as a reduction system.
Catalytic reactions of pyridines. VI. Heterogeneous vapor-phase ring alkylation of pyridines with alcohols over H+-, Li+-, and alkaline earth cation-exchanged zeolites
Kashiwagi,Fujiki,Enomoto
, p. 2575 - 2578 (1982)
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Effects of 15-Crown-5 on Reactions of Dialkylmagnesium Compounds
Richey, Herman G.,King, Bruce A.
, p. 4672 - 4674 (1982)
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Manganese-Catalyzed Kumada Cross-Coupling Reactions of Aliphatic Grignard Reagents with N-Heterocyclic Chlorides
Petel, Brittney E.,Purak, Merjema,Matson, Ellen M.
, p. 1700 - 1706 (2018)
Herein we report the use of manganese(II) chloride for the catalytic generation of C(sp 2)-C(sp 3) bonds via Kumada cross-coupling. Rapid and selective formation of 2-alkylated N-heterocyclic complexes were observed in high yields with use of 3 mol% MnCl 2 THF 1.6 and under ambient reaction conditions (21 °C, 15 min to 20 h). Manganese-catalyzed cross-coupling is tolerant toward both electron-donating and electron-withdrawing functional groups in the 5-position of the pyridine ring, with the latter resulting in an increased reaction rate and a decrease in the amount of nucleophile required. The use of this biologically and environmentally benign metal salt as a catalyst for C-C bond formation highlights its potential as a catalyst for the late-stage functionalization of pharmaceutically active N-heterocyclic molecules (e.g., pyridine, pyrazine).
Zirconium-Catalyzed Amine Borane Dehydrocoupling and Transfer Hydrogenation
Erickson, Karla A.,Stelmach, John P. W.,Mucha, Neil T.,Waterman, Rory
, p. 4693 - 4699 (2015)
κ5-(Me3SiNCH2CH2)2N(CH2CH2NSiMe2CH2)Zr (1) has been found to dehydrocouple amine borane substrates, RR′NHBH3 (R = R′ = Me; R = tBu, R′ = H; R = R′ = H), at low to moderate catalyst loadings (0.5-5 mol %) and good to excellent conversions, forming mainly borazine and borazane products. Other zirconium catalysts, (N3N)ZrX [(N3N) = N(CH2CH2NSiMe2CH2)3, X = NMe2 (2), Cl (3), and OtBu (4)], were found to exhibit comparable activities to that of 1. Compound 1 reacts with Me2NHBH3 to give (N3N)Zr(NMe2BH3) (5), which was structurally characterized and features an η2 B-H σ-bond amido borane ligand. Because 5 is unstable with respect to borane loss to form 2, rather than β-hydrogen elimination, and 2-4 do not exhibit X ligand loss during catalysis, dehydrogenation is hypothesized to proceed via an outer-sphere-type mechanism. This proposal is supported by the catalytic hydrogenation of alkenes by 2 using amine boranes as the sacrificial source of hydrogen.
Palladium nanoparticles supported on magnesium hydroxide fluorides: A selective catalyst for olefin hydrogenation
Acham, Vaibhav R.,Biradar, Ankush V.,Dongare, Mohan K.,Kemnitz, Erhard,Umbarkar, Shubhangi B.
, p. 3182 - 3191 (2014)
A one-pot synthesis of palladium nanoparticles supported on magnesium hydroxide fluoride has been performed with the fluorolytic sol-gel method. The prepared catalysts were characterized by using various physicochemical techniques. The sol-gel method led to high surface area (> 135 m2g-1), mesoporous catalysts (pore volume=0.19-0.23 cm3g-1, pore diameter= 3-5 nm) with uniformly dispersed palladium nanoparticles approximately 2 nm in diameter on the surface. The catalysts synthesized by using different concentrations of aqueous hydrofluoric acid exhibited changing surface and acidic properties. Very high dispersion of palladium on magnesium fluoride (47%) was obtained with 1 wt% palladium loading. The catalysts were used for hydrogenation of various olefins in the presence of other organic functionalities at room temperature and atmospheric hydrogen pressure. Various substituted olefins were hydrogenated with almost 100% conversion and selectivity. The catalysts were recycled efficiently over five cycles without appreciable loss in catalytic activity. There was no palladium leaching under the reaction conditions, which was confirmed by inductively coupled plasma atomic emission spectroscopy analysis. Activation of olefin on the catalyst surface could not be observed by in situ FTIR studies, indicating facile activation of hydrogen on the palladium supported on magnesium hydroxide fluoride.
Iron-Catalyzed Homogeneous Hydrogenation of Alkenes under Mild Conditions by a Stepwise, Bifunctional Mechanism
Xu, Ruibo,Chakraborty, Sumit,Bellows, Sarina M.,Yuan, Hongmei,Cundari, Thomas R.,Jones, William D.
, p. 2127 - 2135 (2016)
Hydrogenation of alkenes containing polarized C=C double bonds has been achieved with iron-based homogeneous catalysts bearing a bis(phosphino)amine pincer ligand. Under standard catalytic conditions (5 mol % of (PNHPiPr)Fe(H)2(CO) (PNHPiPr = NH(CH2CH2PiPr2)2), 23 °C, 1 atm of H2), styrene derivatives containing electron-withdrawing para substituents reacted much more quickly than both the parent styrene and substituted styrenes with an electron-donating group. Selective hydrogenation of C=C double bonds occurs in the presence of other reducible functionalities such as -CO2Me, -CN, and N-heterocycles. For the α,β-unsaturated ketone benzalacetone, both C=C and C=O bonds have been reduced in the final product, but NMR analysis at the initial stage of catalysis demonstrates that the C=O bond is reduced much more rapidly than the C=C bond. Although Hanson and co-workers have proposed a nonbifunctional alkene hydrogenation mechanism for related nickel and cobalt catalysts, the iron system described here operates via a stepwise metal-ligand cooperative pathway of Fe-H hydride transfer, resulting in an ionic intermediate, followed by N-H proton transfer from the pincer ligand to form the hydrogenated product. Experimental and computational studies indicate that the polarization of the C=C bond is imperative for hydrogenation with this iron catalyst.
Synthesis, Characterization, and Reactivity of a High-Spin Iron(II) Hydrido Complex Supported by a PNP Pincer Ligand and Its Application as a Homogenous Catalyst for the Hydrogenation of Alkenes
Ott, Jonas C.,Blasius, Clemens K.,Wadepohl, Hubert,Gade, Lutz H.
, p. 3183 - 3191 (2018)
This study focused on the synthesis and characterization of a range of low-valent, high-spin iron(II) complexes supported by a carbazole-based PNP pincer-type ligand. The addition of the lithiated ligand (PNP)Li to FeCl2(THF)1.5 yielded the chlorido complex (PNP)FeCl (1), which could be readily converted to the four-coordinate iron(II) alkyl complexes (PNP)FeR [R = CH2SiMe3 (3a), Me (3b), CH2Ph (3c)]. These iron(II) complexes were fully characterized by X-ray analysis and a comprehensive, density-functional-theory-assisted study with complete assignment of their paramagnetic 1H and 13C NMR spectra. Treatment of 1 with KHBEt3 or the addition of molecular hydrogen to (PNP)FeR afforded a high-spin iron(II) PNP hydrido complex, which was identified as the dimer [(PNP)Fe(μ-H)]2 (4) with two bridging hydrido ligands between the iron centers. Exposing complexes 1 and 4 to carbon monoxide led to the corresponding six-coordinate, diamagnetic complexes (PNP)Fe(CO)2Cl (2) and (PNP)Fe(CO)2H (5), of which 2 was present as cis/trans isomers. Furthermore, 4 was found to be an active catalyst for the hydrogenation of alkenes.
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Minisci et al.
, p. 4083,4087, 4091 (1970)
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Metal-Organic Framework-Confined Single-Site Base-Metal Catalyst for Chemoselective Hydrodeoxygenation of Carbonyls and Alcohols
Antil, Neha,Kumar, Ajay,Akhtar, Naved,Newar, Rajashree,Begum, Wahida,Manna, Kuntal
supporting information, p. 9029 - 9039 (2021/06/28)
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.
Selective Transfer Semihydrogenation of Alkynes with H2O (D2O) as the H (D) Source over a Pd-P Cathode
Liu, Cuibo,Lu, Siyu,Wang, Changhong,Wu, Yongmeng,Zhang, Bin
supporting information, p. 21170 - 21175 (2020/09/11)
We reported a selective semihydrogenation (deuteration) of numerous terminal and internal alkynes using H2O (D2O) as the H (D) source over a Pd-P alloy cathode at a lower potential. P-doping caused the enhanced specific adsorption of alkynes and the promoted intrinsic activity for producing adsorbed atomic hydrogen (H*ads) from water electrolysis. The semihydrogenation of alkynes could be accomplished at a lower potential with up to 99 % selectivity and 78 % Faraday efficiency of alkene products, outperforming pure Pd and commercial Pd/C. This electrochemical semihydrogenation of alkynes might proceed via a H*ads addition pathway rather than a proton-coupled electron transfer process. The decreased amount of H*ads at a lower potential and the more preferential adsorption of the Pd-P to C≡C π bond than C=C moiety resulted in the excellent alkene selectivity. This method was capable of producing mono-, di-, and tri-deuterated alkenes with up to 99 % deuterium incorporation.
