- Copper-Catalyzed Regioselective Cleavage of C?X and C?H Bonds: A Strategy for Sulfur Dioxide Fixation
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The first example of direct fixation of sulfur dioxide between heteroaryls and aryl halides has been developed via copper-catalyzed regioselective cleavage of C?X and C?H bonds under base-free and ligand-free conditions by using DABSO (1,4-diazabicyclo[2.2.2]octane bis(sulfur dioxide)) as a solid and bench-stable sulfur dioxide surrogate. This mild protocol results in double C?S bond-forming reactions from simple precursors in the absence of prefunctionalized organometallic reagents, arenediazonium salts, and iodonium salts which extends the still limited number of sulfur dioxide fixation strategies.
- Yang, Daoshan,Sun, Pengfei,Wei, Wei,Liu, Fengjuan,Zhang, Hui,Wang, Hua
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- Amidinatogermylene Metal Complexes as Homogeneous Catalysts in Alcoholic Media
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A series of transition-metal complexes containing the bulky amidinatogermylene Ge(tBu2bzam)tBu (1; tBu2bzam = N,N′-bis(tert-butyl)benzamidinate) as a ligand have been prepared and characterized. While
- álvarez-Rodríguez, Lucía,Cabeza, Javier A.,Fernández-Colinas, José M.,García-álvarez, Pablo,Polo, Diego
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- Efficient continuous-flow HD exchange reaction of aromatic nuclei in D2O/2-PrOH mixed solvent in a catalyst cartridge packed with platinum on carbon beads
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Herein, a continuous-flow deuteration methodology for various aromatic compounds is developed based on heterogeneous platinum-catalyzed hydrogen-deuterium exchange. The reaction entails the transfer of a substrate dissolved in a mixed solvent of 2-propanol and deuterium oxide into a catalyst cartridge packed with platinum on carbon beads (Pt/CB). Pt/ CB could be continuously used without significant deterioration of catalyst activity for at least 24 h. Deuteration proceeded within 60 s of the substrate solutions being passed through the Pt/CB layer in the Pt/CB-packed cartridge.
- Park, Kwihwan,Ito, Naoya,Yamada, Tsuyoshi,Sajiki, Hironao
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supporting information
p. 600 - 605
(2021/03/29)
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- H-D Exchange Deuteration of Arenes at Room Temperature
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Arene nuclei efficiently underwent the hydrogen (H)-deuterium (D) exchange reaction catalyzed by platinum group metals on carbon in a mixed solvent of 2-propanol and D2O at room temperature to produce deuterium-labeled arenes. Platinum on carbon (Pt/C) and iridium on carbon (Ir/C) were applicable catalysts, and the various arenes bearing a carbonyl group, fluorine, phenolic hydroxy group, amino group, or phosphonic acid on the aromatic nucleus were effectively deuterated. Nonheating conditions are valuable for the scalable industrial preparation.
- Sawama, Yoshinari,Nakano, Akihiro,Matsuda, Takumi,Kawajiri, Takahiro,Yamada, Tsuyoshi,Sajiki, Hironao
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supporting information
p. 648 - 653
(2019/02/14)
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- Mono and dimetallic pyrene-imidazolylidene complexes of iridium(III) for the deuteration of organic substrates and the C-C coupling of alcohols
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Three different Ir(iii) complexes with pyrene-containing N-heterocyclic carbenes have been prepared and characterized. Two complexes contain a monodentate pyrene-imidazolylidene ligand, and have the formulae [IrCp?Cl2(pyrene-NHC)] and [IrCp?(CO3)(pyrene-NHC)]. The third complex is a dimetallic complex with a pyrene-di-imidazolylidene bridging ligand, with the formula [{IrCp?(CO3)}2(μ-pyrene-di-NHC)]. The catalytic activity of the three complexes was tested in the H/D exchange of organic substrates, and in the β-alkylation of 1-phenylethanol with primary alcohols. In the deuteration of organic substrates, the carbonate complexes are active even in the absence of additives. The dimetallic complex is the most active one in the catalytic coupling of alcohols, a result that may be interpreted as a consequence of the cooperativity between the two metal centres.
- Iba?ez,Poyatos,Peris
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p. 14154 - 14159
(2016/11/15)
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- Iron-Catalyzed Cross-Coupling of Alkenyl Acetates
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Stable C-O linkages are generally unreactive in cross-coupling reactions which mostly employ more electrophilic halides or activated esters (triflates, tosylates). Acetates are cheap and easily accessible electrophiles but have not been used in cross-couplings because the strong C-O bond and high propensity to engage in unwanted acetylation and deprotonation. Reported herein is a selective iron-catalyzed cross-coupling of diverse alkenyl acetates, and it operates under mild reaction conditions (0 C, 2 h) with a ligand-free catalyst (1-2 mol%). Iron clad: Acetates are underutilized electrophiles in metal-catalyzed cross-coupling reactions because of the strong alkenyl C-O bond and their propensity to engage in unwanted reactions. Combination of a ligand-free low-valent Fe catalyst with nucleophilic organomagnesium reagents, low temperature, and short reaction times results in highly selective cross-couplings with alkenyl acetates.
- G?rtner, Dominik,Stein, André Luiz,Grupe, Sabine,Arp, Johannes,Von Wangelin, Axel Jacobi
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supporting information
p. 10545 - 10549
(2015/09/02)
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- Platinum on carbon-catalyzed H-D exchange reaction of aromatic nuclei due to isopropyl alcohol-mediated self- activation of platinum metal in deuterium oxide
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An efficient and simple deuteration method of arenes using the platinum on carbon-isopropyl alcohol-cyclohexane-deuterium oxide combination under hydrogen gas-free conditions was accomplished. Since the hydrogen-deuterium exchange reaction cannot be promoted without isopropyl alcohol, zerovalent platinum metal (on carbon) is self-activated by the in situ-generated very low amount of hydrogen or hydrogen-deuterium gas derived from isopropyl alcohol or isopropyl alcohol-d1. Deuterium-labeled compounds with high deuterium contents can be easily isolated by the filtration of platinum on carbon and simple extraction. The present hydrogen gas-free method is safe from the viewpoint of process chemistry and various arenes possessing a variety of reducible functionalities within the molecule could be effectively and directly deuterium-labeled without undesired reduction. Copyright
- Sawama, Yoshinari,Yamada, Tsuyoshi,Yabe, Yuki,Morita, Kosuke,Shibata, Kyoshiro,Shigetsura, Masahiro,Monguchi, Yasunari,Sajiki, Hironao
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supporting information
p. 1529 - 1534
(2013/06/27)
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- Highly reactive porphyrin-iron-oxo derivatives produced by photolyses ofmetastable porphyrin-iron(IV) diperchlorates
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Photolyses of metastable porphyrin-iron(IV) diperchlorates in laser flash photolysis reactions gave highly reactive transients. The systems studied were 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetramesitylporphyrin (TMP), and 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP). The new species, which decayed within milliseconds in acetonitrile solutions, were shown to react with organic substrates by oxo-transfer reactions involving insertions into carbon-carbon double bonds of alkenes and styrenes or benzylic carbon-hydrogen bonds of arenes. The order of reactivity was OEP > TPP > TMP. Second-order rate constants for reactions with several substrates at 22 °C were determined; representative values of rate constants for the TPP derivative were k = 8.6 × 105 M-1 s-1 for styrene, k = 2.5 × 106 M-1 s-1 for cyclohexene, and k = 7.7 × 104M-1 s-1 for ethylbenzene. These porphyrin-iron-oxo transients reacted 4-5 orders of magnitude faster than the corresponding iron(IV)-oxo porphyrin radical cations with rate constants similar to those of porphyrin-manganese(V)-oxo derivatives. Rate constants for oxidations of benzylic C-H positions of arenes correlated with the C-H bond dissociation energies, and Hammett correlations for reactionswith substituted styrenes had p+ values ranging from-0.5 to- 0.7, reflecting electrophilic character of the oxidants and their high reactivity. On the basis of their unique UV-visible spectra, high reactivities, and oxo-transfer properties, the new transients are tentatively identified as porphyrin-iron(V)-oxo perchlorates, electronic isomers (or valence tautomers) of well-known iron(IV)-oxo porphyrin radical cations.
- Pan, Zhengzheng,Wang, Qin,Sheng, Xin,Horner, John H.,Newcomb, Martin
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experimental part
p. 2621 - 2628
(2009/09/07)
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- Toward the creation of NMR databases in chiral solvents for assignments of relative and absolute stereochemistry: proof of concept.
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[structure: see text] An NMR database approach in a chiral solvent allows us to predict both relative and absolute stereochemistry of an unknown compound without degradation and/or derivatization. N,alpha-Dimethylbenzylamine (DMBA) is a suitable solvent for this purpose. Using the C.5-C.10 portion of oasomycin A, the feasibility and reliability of this approach is demonstrated.
- Kobayashi,Hayashi,Tan,Kishi
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p. 2245 - 2248
(2007/10/03)
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- Direct observation of deuterium migration in crystalline-state reaction by single-crystal neutron diffraction. II. 3-1 photoisomerization of a cobaloxime complex
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Single crystal neutron diffraction analysis of photo-exposed (3-cyanopropyl-d2 α,α)-[(R)-1-phenylethylamine-d 11]bis(dimethylglyoximato-d14)cobalt(III) was carried out in order to clarify the mechanism of the cr
- Ohhara, Takashi,Harada, Jun,Ohashi, Yuji,Tanaka, Ichiro,Kumazawa, Shintaro,Niimura, Nobuo
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p. 245 - 253
(2007/10/03)
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- Preparative supercritical deuterium exchange in arenes and heteroarenes
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Deuterated homo- and heterocyclic aromatic substrates bearing various functionalities were prepared by isotope exchange in supercritical deuterium oxide, with little or no formation of byproducts. Equilibration was attained rapidly (1-24 hrs), and deuterium exchange extended to alpha positions of alkyl homologs. Nitro- and haloarenes, thioethers, telluroethers, and some heterocyclic substrates were unstable.
- Junk, Thomas,Catallo, W. James
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p. 3445 - 3448
(2007/10/03)
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- Infrared studies of acetophenone and its deuterated derivatives
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The i.r. spectra of acetophenone and their deuterated analogues (-d3, -d5, -d8) in the liquid-phase have been recorded and analyzed in the range 4000-130 cm-1.Additional data on band contours in the gas-phase, in conjuction with the deuteration effects, allowed us to assign all the fundamentals for the four isotopic varieties.A valence force field calculation was also used to support the proposed assignment.
- Gambi, A.,Giorgianni, S.,Passerini, A.,Visinoni, R.,Ghersetti, S.
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p. 871 - 878
(2007/10/02)
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