Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. AcOH) provides a mild method for reducing nitro groups to amines in the presence of other reducible groups. * In Clemmensen reduction, the amalgamated zinc in HCl is used as reducing agent. Zinc-promoted reactions. A few require preparation and immediate use, including zinc–copper couple and zinc/silver couples. Sigitas Stončius, Algirdas Neniškis, Nagarajan Loganathan, Ola F. Wendt. respectively. The lone pair of electrons on the hydride ion forms a bond with the carbon, and the electrons in one of the carbon-oxygen bonds are repelled entirely onto the oxygen, giving it a negative charge. For moisture-sensitive substrates, ethyl acetate can be added to consume any excess LAH and the reduction The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. 8. [6], Two-electron reducing agents, the most prominent of which is zinc metal, undergo direct oxidative addition to monohalo ketones to afford metal enolates in which the oxidation state of the metal has increased by two. Reduction of 20-oxo-5, 6, 17-tribromopregnane-3β, 16β-diol 3-acetate (V) over Raney nickel in pyridine afforded 20-oxo-5, 16-pregnadien-3β-ol acetate (II). All the reactions can be performed in scCO2 with equal or even better results than in conventional organic solvents, owing to the high diffusion and low viscosity of scCO2. A novel method for reducing aldehydes to the corresponding alcohols with high selectivity in supercritical carbon dioxide using water as hydrogen donor and Zn dust as electron donor has been developed. Fluorination of some fluorine-containing oxo esters by sulfur tetrafluoride. [1] 2-Oxyallyl metal intermediates may also intercept nucleophiles in a process that involves umpolung at the α carbon. hydrodebromination to give 3-bromoisothiazole-4-carbonitrile 3 in 70e74% yield. Zdeněk Sofer, Ondřej Jankovský, Alena Libánská, Petr Šimek, Michal Nováček, David Sedmidubský, Anna Macková, Romana Mikšová, Martin Pumera. The behaviour of alkyl substituted 1,3-diketones. Additive condensation of thiophenol with 3-bromothiachromone 1, 1-dioxide in the presence of alkali afforded 2-phenylthio-thiachromone 1, 1-dioxide. Die sehr selektiven Reduktionen mit komplexen Borhydriden haben in letzter Zeit große Bedeutung erlangt. A Barbier-type allylation of aldimines by allylic acetates in the presence of zinc dust and a simple cobalt halide catalyst takes place in acetonitrile to give the corresponding homoallylic amines in good yields. All products are fully characterized. For instance, a synthesis of scopine uses the [4+3] cycloaddition of N-methoxycarbonylpyrrole and α,α,α',α'-tetrabromoacetone as a key step. In the Fieser work-up, following reduction with n grams of LAH, careful successive dropwise addition of n mL of water, n mL of 15% NaOH solution, and 3n mL of water provides a granular inorganic precipitate that is easy to rinse and filter. Citations are the number of other articles citing this article, calculated by Crossref and updated daily. The α-halo ketones are readily prepared from ketones by various ketone halogenation reactions, and the products are reactive intermediates that can be used for a variety of other chemical reactions. A mild and an efficient system has been developed for the reduction of aromatic aldehydes and ketones to their corresponding alcohols in good yield using inexpensive commercial zinc dust as catalyst and diammonium hydrogen phosphite as a hydrogen donor. Zinc-promoted reactions. Reduction to hydroxylamines. The reduction of α-halo ketones generates a variety of product structures that may exhibit unique substitution patterns and reactivity. Synthesis ofo-andm-carborane derivatives of [2,2]paracyclophane and abnormal Clemmensen reduction of ketones of the [2,2]paracyclophane and carborane series. Ring-Contraction Disproportionation/Spirocyclization Cascade Reaction of Isochromeno[4,3-b]indol-5(11H)-ones: Synthesis of N-Unsubstituted Spirocycles. bromo and phenylthio groups were respectively introduced into the 2-position. Substituent effects are discussed. Zn–H2O–CO2 is an excellent reducing Examples. The nitro group was one of the first functional groups to be reduced. The reduction of nitro compounds are chemical reactions of wide interest in organic chemistry. Jian Zhang, Yong-Qiang Wang, Xin-Wei Wang, and Wei-Dong Z. Li . For instance, reduction of α,α'-dihalo ketones leads to 2-oxyallyl metal complexes, which participate in [4+3] and [3+2] cycloaddition reactions as the 2π component. Examples. AcOH) provides a mild method for reducing nitro groups to amines in the presence of other reducible groups. Monohalo ketones are reduced by both one-electron and two-electron reducing agents to afford the parent ketones, derivatives functionalized with electrophiles, or products of dimerization. Join ResearchGate to find the people and research you need to help your work. Redox induced radical and radical ionic carbon-carbon bond forming reactions. Information. Users are Erik Hedenström, Ba-Vu Nguyen, Louis A. Silks. For permission to reproduce, republish and Electronic Supporting Information files are available without a subscription to ACS Web Editions. However, since this reagent was generated by treatment of molybdenyl chloride with zinc dust, the role of some suspended metal in the sulfoxide reduction cannot be assessed. Finally, the 3-bromoisothiazole 3 is readily converted into both 3-bromoisothiazole-4-carboxamide The absolute configurations of these compounds were assigned based on chemical modifications and their specific rotations. Fragmentation of the resulting radical anion yields an organic radical and halide anion. Zinc-promoted reactions. Reduction of benzophenone in glacial acetic acid. You’ve supercharged your research process with ACS and Mendeley! http://pubs.acs.org/page/copyright/permissions.html. Do enzymes recognise remotely located stereocentres? Highly enantioselective Candida rugosa lipase-catalysed esterification of the 2- to 8-methyldecanoic acids. Depending on the conditions employed, geminal dihalo ketones may be reduced to the parent ketone, monohalo ketone, or functionalized monohalo ketone with organocuprates. The conversion can be effected by many reagents. The reaction can also be carried out with zinc dust and ammonium chloride [citation needed]: R-NO 2 + 4 NH 4 Cl + 2 Zn → R-NH-OH + 2 ZnCl 2 + 4 NH 3 + H 2 … Dtsch. Fragmentation of the resulting radical anion yields an organic radical and halide anion. Understanding the Guanidine-Like Cationic Moiety for Optimal Binding into the DNA Minor Groove. In the example below, the product distribution is solvent dependent[16]. 1. http://pubs.acs.org/page/copyright/permissions.html, https://doi.org/10.1021/acs.chemmater.5b01527, https://doi.org/10.1007/s12274-014-0633-6, https://doi.org/10.1002/9781118681299.ch6, https://doi.org/10.1016/j.tet.2011.03.065, https://doi.org/10.1002/9780470638859.conrr149, https://doi.org/10.1002/9780470682531.pat0139, https://doi.org/10.1016/j.tet.2006.04.038, https://doi.org/10.1016/j.jelechem.2005.03.041, https://doi.org/10.1007/978-3-322-96805-0_4, https://doi.org/10.1016/j.tet.2003.10.068, https://doi.org/10.1016/S0957-4166(02)00172-6, https://doi.org/10.1515/MGMC.1999.22.2.89, https://doi.org/10.1007/978-3-322-94077-3_23, https://doi.org/10.1016/0022-1139(95)03272-F, https://doi.org/10.1016/0040-4020(95)00434-A, https://doi.org/10.1016/0304-5102(93)E3136-O, https://doi.org/10.1016/S0040-4020(01)87006-X, https://doi.org/10.1007/978-3-322-94015-5_22, https://doi.org/10.1016/S0040-4020(01)80246-5, https://doi.org/10.1016/S0040-4020(01)85756-2, https://doi.org/10.1016/S0040-4039(00)61287-X. Solvents- MeOH, EtOH, EtOAc, AcOH, Et 2O, Hexanes Decreasing order of activity H 2, Pd-C H 2, Pt-C H 2, Rh/Al 2O 3 H 2, Ra-Ni Decreasing order of reactivity Transition metals adsorbed onto a solid support RNO 2 ’ RCOCl’ R RR O RR RCN’ 3. Zhilong Li, Fanny C. F. Ip, Nancy Y. Ip, Rongbiao Tong. * The C=O group is converted to CH 2 group. (scCO2). Examples . The reactions include oxidation, reduction, carbonylation, radical addition, C-C coupling and cycloaddition reactions. The dibromoisothiazole 1 reacts with Zn dust in Parichatr Vanalabhpatana, Dennis G. Peters, Jonathan A. Karty. The corresponding alcohols were obtained in good yields Part 5. Zinc-promoted reactions. Ges. Access scientific knowledge from anywhere. Xiang Zhang, Guangshuai Zhou, Yong Zhang, Daisy Zhang-Negrerie, Yunfei Du, and Kang Zhao . Zinc-promoted reactions. Treatment of enolates derived from either one- or two-electron reducing agents with an electrophile affords α-functionalized ketones as the final product. Hydrogen (zinc dust and acetic acid), bromine, 2, 3-dimethylbutadiene, hydrogen bromide, and thiophenol underwent addition to this double bond to form 4-thiachromanone 1, 1-dioxide and their derivatives but in the case of two latter reagents, Reduction of diosone diacetate (Ia), 20-oxo-5-pregnene-3β, 16β-diol 3-acetate (Ib), and 20-oxo-5-pregnene-3β, 16β-diol diacetate (Ic) with zinc dust and acetic acid was found to result in reductive cleavage of the hydroxyl or acyloxy group in 16β-position to form 20-oxo-5-pregnen-3β-ol acetate (III).
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