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1.
First Isolation and Characterization of the Highly Coordinated Group 14 Enolates: Effects of the Coordination Controls on the Geometry and Tautomerization of Germyl Enolates
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Dr. Akihito Konishi Yohei Minami Takahisa Hosoi Kouji Chiba Prof. Dr. Makoto Yasuda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(36):12688-12691
The Group 14 enolates play an important part in many organic reactions. Herein, the reduction of an α‐bromo ketone with germanium(II) salts cleanly afforded the corresponding germyl enolate as an isolatable species. This experimental reductive generation of a germyl enolate enabled us to characterize both C‐ and O‐bound tautomers derived from an identical precursor and to unveil the tautomeric mechanisms, including the kinetic parameters and the relative stability of these tautomers, along with confirmation from DFT calculations. Moreover, the highly coordinated germyl enolates were isolated by a stabilization process induced by adding ligands. All products were characterized by NMR spectroscopy and X‐ray crystallography. 相似文献
2.
Seema Kanwar 《合成通讯》2013,43(16):2149-2155
Abstract α‐Cyano and α‐chloro β‐lactams are obtained in a one‐step reaction at a temperature of less than ?78°C by condensation of imines with ester enolates derived from ethyl α‐cyano and α‐chloro acetates. 相似文献
3.
p-Terphenylphosphines bearing one or two hydroxy groups were used as ligands to palladium in the cross-coupling of dibromophenols, dibromoanilines, and their congeners with Grignard reagents. High ortho-selectivity that cannot be achieved using other phosphine ligands was observed. ortho-Preference was also observed in competitive cross-coupling reactions of two substrates. A significant effect of the concentration of the Grignard reagent on the ortho-selectivity was observed, when the hydroxylated terphenylphosphines were used. Kinetic studies on this effect showed that high concentrations of the Grignard reagent retard the cross-coupling reaction only at the para-position, but not at the ortho-position. 相似文献
4.
Among the three types of reagents from PhMgX (X=Br, Cl) and CuCN for phenylation of 4-cyclopentene-1,3-diol monoacetate, PhMgCl/CuCN (cat.) and Ph2Cu(CN)(MgCl)2 in THF afforded the trans-1,4-isomer efficiently (82-87% yields, 91-93% regioselectivity). Similarly, o- and p-RC6H4MgCl (R=Me, OMe, CH2CH) in combination with CuCN furnished good to excellent reactivity and regioselectivity. As an application, a three-step synthesis of dihydromultifidene was accomplished successfully. 相似文献
5.
Motohiro Sonoda Shoko Kinoshita Thanh Luu Hiroshi Fukuda Koji Miki Rui Umeda 《合成通讯》2013,43(18):3315-3323
Selective lithiation of 3-bromothiophene was accomplished under controlled conditions without formation of undesired thienyllithium compounds. A thienyl Grignard reagent derived from 2-bromo-3-iodothiophene was transformed into 2-bromo-3-formylthiophene in high selectivity by formylation with dimethylformamide (DMF) at optimal reaction temperature. 相似文献
6.
Andrei S. Batsanov Philip D. Bolton Royston C.B. Copley Matthew G. Davidson Judith A.K. Howard Christian Lustig Richard D. Price 《Journal of organometallic chemistry》1998,550(1-2)
Imino(triphenyl)phosphorane, Ph3P=NH 1a, is metallated by ethylmagnesium chloride to give the N-magnesioiminophosphorane complex [Ph3P=NMgCl·O=P(NMe2)3]2 4, whose X-ray structure has been determined. 相似文献
7.
Zhao Yang WANG Jia Ling CUI Bao Shan DU* Qing Hua CHEN Department of Chemistry Beijing Normal University Beijing Present address: Dept. of Chem. South China Nor. Univ Guangzhou Present address: School of Pharm. Beijing Univ 《中国化学快报》2001,(4)
Recently, much effort has been made in the development of generally applicable organic synthesis of 5-alkyloxy-2(5H)-furanones due to their essential structure entities in the synthesis of some biologically active natural products and their application as useful intermediates in organic synthesis1. Their reactions such as Michael addition, Diels-Alder reaction and photocatalyzed conjugate addition have been studied extensively2-4.However, Michael addition reaction of Grignard reagents to 5-m… 相似文献
8.
Masakazu Kogami 《合成通讯》2013,43(5):681-688
Lithium chloride was found to accelerate formation of the Grignard reagent from inactive 3-bromo-2-methylthiophene (1) and commercial magnesium metal. Based on this finding, a convenient and potentially scalable preparation of ethyl 2-methylthiophene-3-carboxylate (3) was achieved. In addition, this process has been found to provide a new, general approach to 3-substituted 2-methylthiophenes. 相似文献
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10.
D‐Glucosamine in iron‐catalysed cross‐coupling reactions of Grignards with allylic and vinylic bromides: application to the synthesis of a key sitagliptin precursor
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A sustainable D ‐glucosamine ligand is successfully introduced into iron‐catalysed C ? C cross‐coupling reactions for the first time. The Fe(acac)2/D ‐glucosamine·HCl/Et3N catalytic system was effective at 5 mol% loading in coupling reactions of Grignard reagents with organic bromides. Moderate to high efficiency was achieved with preserved stereochemistry when allyl (Csp3) or alkenyl (Csp2) bromides were coupled with phenylmagnesium (Csp2) or benzylmagnesium (Csp3) bromides. The catalytic system developed was also successfully applied for the novel and economic preparation of a Michael‐acceptor‐like starting material used in an alternative synthesis of the drug sitagliptin, a known blockbuster for the treatment of type II diabetes mellitus. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
11.
Jeffrey Axten Jennifer Troy Peter Jiang Mendel Trachtman Charles W. Bock 《Structural chemistry》1994,5(2):99-108
Ab initio molecular orbital calculations are used to study the modified Schlenk equilibrium: 2RMgCl (RMgCl)2 MgR2 + MgCl2 Mg(Cl2)MgR2 with R=H and CH3. In the absence of any solvents, calculations indicate that the formation of the various possible bridged dimers (RMgCl)2 is substantially exothermic. However, using dimethylether as a model solvent, we show that the formation of the dimer (Me2O)(CH3)Mg(Cl2)Mg(CH3)(OMe2) is exothermic only when entropic effects are included. 相似文献
12.
Guillaume Vives 《Tetrahedron letters》2006,47(49):8741-8744
In order to demonstrate a movement of rotation in a family of rotary molecular motors, 1-bromo-1-(4-tolyl)-2,3,4,5-tetra(4-bromophenyl) cyclopentadiene has been synthesized. The coordination of this C2v cyclopentadiene to a ruthenium trisindazolylborate complex and the quadruple coupling reaction with ethynylferrocene led to the dissymmetrized motor (1). 相似文献
13.
Eiji Ihara Takao Wake Naoki Mokume Tomomichi Itoh Kenzo Inoue 《Journal of polymer science. Part A, Polymer chemistry》2006,44(19):5661-5671
α,α‐Dibromotoluene 1 was found to be polymerized by the reaction with excess Mg to give poly(phenylmethylene)s 2 , whose main chains were partially dehydrogenated to carbon–carbon double bonds (C?C). The C?Cs in 2 can be brominated by treatment with Br2. The polymerization mechanism was presumed to include the formation of Grignard reagents of various species with benzylic C? Br bonds and the nucleophilic attacks of the Grignard reagents to various compounds with benzylic C? Br bonds. Copolymerization of 1 with dichlorodimethylsilane successfully proceeded. Mg/Cu‐mediated copolycondensation of 1 with 1,6‐dibromohexane proceeded to give polymers that have similar compositions to those of random copolymers of ethylene and styrene. © 2006Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5661–5671, 2006 相似文献
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The effect of adsorption of the oxidant (EtBr) and aprotic dipolar solvent molecules on the electronic structure and properties
of Mg
n
(n ≤ 50) clusters simulating the surface of metallic magnesium was studied by the B3PW91/6-31G(d) density functional method.
It was found that the work function of an electron from the cluster monotonically decreases as the donor ability of the adsorbed
molecules increases. The experimentally measured rate of the magnesium oxidation by EtBr correlates with the negative Mulliken
charge density of the first coordination sphere of the surface adsorption site. The results obtained are in agreement with
the experimentally determined work function of electron from metals during adsorption from the gas phase. Presumably, the
rate-limiting step of the Grignard reagent formation is the surface oxidation reaction.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 458–469, March, 2008. 相似文献
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Electrophilic fluorination and fluoroalkylation are one of the most promising and efficient strategies in the synthesis of organofluorine compounds. The rapid progress of this field has been made possible by the emergence of a wide variety of power-variable, readily prepared, and easy-to-handle electrophilic fluorinating and fluoroalkylating reagents. Understanding the relative power of these reagents is thus vital for their use in synthetic transformations. This digest will outline some recent efforts to quantitatively ordering the relative power of electrophilic fluorinating, trifluoromethylating, and trifluoromethylthiolating reagents. 相似文献
19.
Ferreiro M. Luisa Rodríguez-Otero Jesús Cabaleiro-Lago Enrique M. 《Structural chemistry》2004,15(4):323-326
Ab initio and DFT methods were used in combination with various basis sets in order to examine the [4 + 2] Diels–Alder cycloaddition reactions of ethene with 1,3-butadiene, 1,2,4-pentatriene, and 1,2,4,5-hexatetraene with a view to elucidating the role of the allene group in this type of pericyclic reaction. Based on the calculations, the insertion of an allene group decreases the activation energy and increases the exothermal character of the reaction. The decrease is even more marked in the presence of two allene groups, particularly with regard to the reaction enthalpy, which exhibits an additive effect. 相似文献
20.
Francesca Bartoccini Giovanni Piersanti Silvia Armaroli Alberto Cerri Walter Cabri 《Tetrahedron letters》2014
A simple, convenient, and environmentally friendly route to ST1535 employing an iron-catalyzed cross-coupling reaction and butylmagnesium chloride is described. 相似文献