Xi:Irritant;
111-87-5Relevant articles and documents
Oxidation of zinc organometallics prepared by hydrozincation or carbozincation using oxygen
Klement, Ingo,Luetjens, Henning,Knochel, Paul
, p. 3161 - 3164 (1995)
Organozinc compounds prepared by the hydrozincation or carbazincation of functionalized unsaturated molecules can be directly oxidized by oxygen affording alcohols after reductive workup in satisfactory yields.
Regioselective addition of stannylcyanocuprates to acetylenic ethers: A chemical and spectroscopic study
Cabezas,Oehlschlager
, p. 432 - 442 (1994)
The reactions of acetylenic ether 1 with higher order cuprates 2a, 2b and 2c were studied chemically and spectroscopically. Conditions were developed to efficiently and regioselectively prepare α- and β-stannylvinyl ethers. 1H and 13C NMR studies of these reactions suggest that in the presence of HMPA, higher order stannylcyanocuprate, (Bu3Sn)2Cu(CN)Li2, 2a, exists in equilibrium with Gilman cuprate, (Bu3Sn)2CuLi.
Electrophilic Etherification of α-Heteroaryl Carbanions with Monoperoxyacetals as a Route to Ketene O, O- And N, O-Acetals
Paris, Timothy J.,Schwartz, Chris,Willand-Charnley, Rachel
, p. 2369 - 2384 (2021)
Alkyl ketene acetals are useful reactants in a variety of synthetic processes, and yet, there are limited routes to their formation as isolable products. We now report the successful synthesis and isolation of heteroaryl ketene acetals through intermolecular transfer of alkoxyl (δ+OR) from electrophilic peroxides to lithiated benzofurans, indoles, and pyridines. Primary and secondary peroxyacetals enable selective transfer of the nonanomeric alkoxy group in moderate to high yield; substrates bearing an electron-donating substituent show enhanced reactivity toward electrophilic oxygen. Heteroaryl ketene acetals are remarkably stable throughout traditional purification techniques; the superior stability of ketene N,O-acetals compared to ketene O,O-acetals is presumably due to increased aromaticity of the indole and pyridine structures. The presented method overcomes typical problems associated with alkyl ketene acetal synthesis as reported products withstood workup and flash column chromatography procedures.
Highly selective and stable ZnO-supported bimetallic RuSn catalyst for the hydrogenation of octanoic acid to octanol
Hidajat, Marcel Jonathan,Hwang, Dong-Won,Yun, Gwang-Nam
, (2021)
The chemoselective hydrogenation of biomass-derived carboxylic acids is promising for the development of biorefineries. Herein, the selective conversion of octanoic acid to octanol over bimetallic RuSn/ZnO in a fixed-bed continuous reactor system, is reported. Almost complete conversion (99.4 %) of octanoic acid was achieved, with a remarkably high selectivity to octanol (93.0 %), when using specific reaction conditions (300°C, a weight hourly space velocity (WHSV) of 2 h?1, and 30 atm H2). Characterizations of the catalysts by BET, CO pulse chemisorption, ICP-AES, XRD, XPS and STEM-EDS revealed that the addition of Sn to Ru/ZnO resulted in the formation of a Ru3Sn7 alloy phase as well as SnOx. Comparison with Ru/ZnO catalyst gives an insight that the presence of Ru3Sn7 alloy was most likely the active site and it significantly improved the hydrogenation activity and selectivity to octanol. The SnOx and ZnO favored the formation of octyl octanoate by esterification of the formed octanol and octanoic acid, although it was successfully suppressed by optimizing the reaction conditions. Long-term stability tests revealed that RuSn/ZnO retained its activity for 1000 h with no coke formation. This study reveals the potential of RuSn/ZnO for the valorization of medium-chain fatty acids into value-added chemicals.
Identification of a marine NADPH-dependent aldehyde reductase for chemoselective reduction of aldehydes
Li, Guangyue,Ren, Jie,Wu, Qiaqing,Feng, Jinhui,Zhu, Dunming,Ma, Yanhe
, p. 17 - 22 (2013)
A putative aldehyde reductase gene from Oceanospirillum sp. MED92 was overexpressed in Escherichia coli. The recombinant protein (OsAR) was characterized as a monomeric NADPH-dependent aldehyde reductase. The kinetic parameters Km and kcat of OsAR were 0.89 ± 0.08 mM and 11.07 ± 0.99 s-1 for benzaldehyde, 0.04 ± 0.01 mM and 6.05 ± 1.56 s-1 for NADPH, respectively. This enzyme exhibited high activity toward a variety of aromatic and aliphatic aldehydes, but no activity toward ketones. As such, it catalyzed the chemoselective reduction of aldehydes in the presence of ketones, as demonstrated by the reduction of 4-acetylbenzaldehyde or the mixture of hexanal and 2-nonanone, showing the application potential of this marine enzyme in such selective reduction of synthetic importance.
A facile zirconium(IV) chloride catalysed selective deprotection of t-butyldimethylsilyl (TBDMS) ethers
Sharma,Srinivas,Radha Krishna, Palakodety
, p. 4689 - 4691 (2003)
A simple and efficient protocol for the selective deprotection of t-butyldimethylsilyl (TBDMS) ethers using 20 mol% ZrCl4 in 20-45 min and in high yields, is reported, wherein it is demonstrated that acid and base sensitive groups and allylic and benzylic groups are unaffected.
Engineering carboxylic acid reductase for selective synthesis of medium-chain fatty alcohols in yeast
Hu, Yating,Zhu, Zhiwei,Gradischnig, David,Winkler, Margit,Nielsen, Jens,Siewers, Verena
, p. 22974 - 22983 (2020)
Medium-chain fatty alcohols (MCFOHs, C6 to C12) are potential substitutes for fossil fuels, such as diesel and jet fuels, and have wide applications in various manufacturing processes. While today MCFOHs are mainly sourced from petrochemicals or plant oils, microbial biosynthesis represents a scalable, reliable, and sustainable alternative. Here, we aim to establish a Saccharomyces cerevisiae platform capable of selectively producing MCFOHs. This was enabled by tailoring the properties of a bacterial carboxylic acid reductase from Mycobacterium marinum (MmCAR). Extensive protein engineering, including directed evolution, structure-guided semirational design, and rational design, was implemented. MmCAR variants with enhanced activity were identified using a growth-coupled high-throughput screening assay relying on the detoxification of the enzyme’s substrate, medium-chain fatty acids (MCFAs). Detailed characterization demonstrated that both the specificity and catalytic activity of MmCAR was successfully improved and a yeast strain harboring the best MmCAR variant generated 2.8-fold more MCFOHs than the strain expressing the unmodified enzyme. Through deletion of the native MCFA exporter gene TPO1, MCFOH production was further improved, resulting in a titer of 252 mg/L for the final strain, which represents a significant improvement in MCFOH production in minimal medium by S. cerevisiae.
Intrinsic isotope effects suggest that the reaction coordinate symmetry for the cytochrome P-450 catalyzed hydroxylation of octane is isozyme independent
Jones,Rettie,Trager
, p. 1242 - 1246 (1990)
The mechanism of the ω-hydroxylation of octane by three catalytically distinct, purified forms of cytochrome P-450, namely, P-450(b), P-450(c), and P-450(LM2), was investigated by using deuterium isotope effects. The deuterium isotope effects associated with the ω-hydroxylation of octane-1,1,1-2H3, octane-1,8-2H2, and octane-1,1,8,8-2H4 by all three isozymes were determined. From these data the intrinsic isotope effects were calculated and separated into their primary and secondary components. The primary intrinsic isotope effect for the reaction ranged from 7.69 to 9.18 while the secondary intrinsic isotope effect ranged from 1.13 to 1.25. Neither the primary nor secondary isotope effect values were statistically different for any of the isozymes investigated. These data are consistent with a symmetrical transition state for a mechanism involving initial hydrogen atom abstraction followed by hydroxyl radical recombination which is essentially independent of the specific isozyme catalyzing the reaction. It is concluded that (1) in general the porphyrin-[FeO]3+ complex behaves as a source of a triplet-like oxygen atom, (2) the regioselectivity for the site of oxidation is dictated by the apoprotein of the specific isozyme of cytochrome P-450 catalyzing the reaction, and (3) the maximum primary intrinsic isotope effect for any cytochrome P-450 catalyzed oxidation of a carbon center is about 9, assuming no tunneling effects.
Dod-S-Me and methyl 6-morpholinohexyl sulfide (MMS) as new odorless borane carriers
Patra, Pranab K.,Nishide, Kiyoharu,Fuji, Kaoru,Node, Manabu
, p. 1003 - 1006 (2004)
Odorless Dod-S-Me (1) and MMS (3) are developed as efficient borane carriers. The yields of hydroborations and reductions with borane complex 2 of 1 are very high and the recovery of 1 after the reaction is quantitative. The borane complexes 4 and 5 of 3 are also useful. In the latter case chromatographic separation is unnecessary when excess oxidizing agent (alkaline H2O2) is used after hydroboration.
2-pyridylsilyl group as a multifunctional 'phase tag' for solution phase synthesis
Yoshida, Jun-ichi,Itami, Kenichiro,Mitsudo, Koichi,Suga, Seiji
, p. 3403 - 3406 (1999)
2-Pyridyldimethylsilyl (2-PyMe2Si) group was found to serve as effective 'phase tag' for acid-base extraction for solution phase synthesis. Acid-base extraction of octyl(2-pyridyl)dimethylsilane gave rise to 98% recovery. The introduction of 2-PyMe2Si group to organic molecules was easily accomplished by Rh catalyzed hydrosilylation of alkenes with 2- PyMe2SiH. The removal of 2-PyMe2Si group was achieved by the oxidation with H2O2/KF (Tamao oxidation). In order to demonstrate the utility of 2- PyMe2Si group as a 'phase tag', a sequential multi-step transformation was conducted. The products of each steps were easily isolated by acid-base extraction, and were sufficiently pure for the direct use in the next step of the sequence.
