E-Olefins through intramolecular radical relocation

Science ◽  
2019 ◽  
Vol 363 (6425) ◽  
pp. 391-396 ◽  
Author(s):  
Ajoy Kapat ◽  
Theresa Sperger ◽  
Sinem Guven ◽  
Franziska Schoenebeck
Keyword(s):  
Double Bond ◽  
Hydrogen Atom ◽  
Precious Metal ◽  
Room Temperature ◽  
Metal Hydrides ◽  
The Past ◽  
Full Control ◽  
Carbon Double Bond ◽  
Hydrogen Scrambling ◽  
Fragrance Materials

Full control over the selectivity of carbon–carbon double-bond migrations would enable access to stereochemically defined olefins that are central to the pharmaceutical, food, fragrance, materials, and petrochemical arenas. The vast majority of double-bond migrations investigated over the past 60 years capitalize on precious-metal hydrides that are frequently associated with reversible equilibria, hydrogen scrambling, incompleteE/Zstereoselection, and/or high cost. Here, we report a fundamentally different, radical-based approach. We showcase a nonprecious, reductant-free, and atom-economical nickel (Ni)(I)-catalyzed intramolecular 1,3-hydrogen atom relocation to yieldE-olefins within 3 hours at room temperature. Remote installations ofE-olefins over extended distances are also demonstrated.

Synthesis and Spectroscopic Studies of Pentacarbonylfumaronitrile-chromium(0), -molybdenum(0), and -tungsten(0)

1994 ◽  
Vol 49 (8) ◽  
pp. 1059-1062 ◽  
Author(s):  
İzzet A. Mour ◽  
Saim Ozkar ◽  
Cornelius G. Kreiter
Keyword(s):  
Double Bond ◽  
Nmr Spectroscopy ◽  
Nitrogen Atom ◽  
Room Temperature ◽  
Spectroscopic Studies ◽  
Carbon Double Bond ◽  
C Nmr ◽  
And Tungsten

Photolysis of hexacarbonyl-chromium(0), -molybdenum(0), and -tungsten(0) in presence of fumaronitrile yields at room temperature pentacarbonyl-fumaronitrile-chromium(0) (1), - molybdenum(0) (2), and -tungsten(0) (3). The complexes were purified by crystallization and characterized by IR and 13C-NMR spectroscopy. The fumaronitrile ligand is bonded to the M(CO)5 moiety by one nitrile nitrogen atom rather than by the carbon-carbon double bond. In toluene 2 dissociates into fumaronitrile and pentacarbonyl-molybdenum(0), which is stabi­lized by the solvent. Fumaronitrile and solvated pentacarbonyl-molybdenum(0) exist in solu­tion together with 2 in an equilibrium which lies in favour of the former species.

Synthesis and Spectroscopic Study of Pentacarbonyl(η2-tetracyanoethylene) Metal(0) Complexes of the Group 6 B Elements

1994 ◽  
Vol 49 (5) ◽  
pp. 717-720 ◽  
Author(s):  
İzzet A. Mour ◽  
Saim Özkar
Keyword(s):  
Double Bond ◽  
Nmr Spectroscopy ◽  
Spectroscopic Study ◽  
Spectral Data ◽  
Photochemical Reaction ◽  
Room Temperature ◽  
Carbon Double Bond ◽  
Uv Visible ◽  
Metal Ligand ◽  
C Nmr

Pentacarbonyl(η2-tetracyanoethylene) metal(0) complexes of chromium, molybdenum and tung­sten have been synthesized by the photochemical reaction of hexacarbonyl metal(o) with tetra- cyanoethylene in toluene at room temperature. The complexes were purified by chromatography and recrystallization, and characterized by UV- visible, IR and 13C NMR spectroscopy. Tetra- cyanoethylene is symmetrically bonded to the M(CO)5 unit through its carbon-carbon double bond as an η2-ligand. The spectral data are dis­cussed in terms of the metal → ligand π inter­action.

Photochemical Synthesis and Identification of Tetracarbonyl-bis(olefin)metal(0) Complexes of Group VI B Elements

2000 ◽  
Vol 55 (12) ◽  
pp. 1153-1156 ◽  
Author(s):  
İ. Amour Morkan ◽  
A. Uztetik-Morkan
Keyword(s):  
Double Bond ◽  
Spectral Data ◽  
Room Temperature ◽  
Central Atom ◽  
Photochemical Synthesis ◽  
Group Vi ◽  
Carbon Double Bond ◽  
Metal Ligand ◽  
C Nmr

Photolysis of hexacarbonyl metal(0) or tetracarbonyl-bis(1,3-butadiene)metal(0) (metal: chromium, molybdenum, tungsten) in the presence of tetracyanoethylene, TCNE, or fumaronitrile , FN, at room temperature yields fram-bis(μ2-tetracyano-ethylene)tetracarbonyl-chromium(0) (1), -molybdenum(0) (2), -tungsten(0) (3) and trans-bis(fumaronitrile)tetracarbonylchromium(0) (4), -tungsten(0) (5) complexes. The complexes were purified by chromatography and recrystallization and characterized by IR , 1H, 13C NMR and mass spectroscopies. It is shown that two tetracyanoethylene ligands are symmetrically bonded to the M(CO)4 moiety through their carbon-carbon double bond in the form of μ2 -TCNE . The two fumaronitrile ligands are bonded to the central atom through their nitrogen atoms. The spectral data are discussed in terms of metal → ligand π - interaction.

Granular bainite or granular ferrite? A preliminary TEM investigation of an HSLA-100 steel

1991 ◽  
Vol 49 ◽  
pp. 584-585
Author(s):  
R. Varughese ◽  
S. W. Thompson ◽  
P. R. Howell
Keyword(s):  
Room Temperature ◽  
Transformation Products ◽  
Accurate Description ◽  
Granular Bainite ◽  
Preliminary Results ◽  
The Past ◽  
Light Micrograph ◽  
Multiphase Reaction ◽  
Detailed Nature

Ever since Habraken and Economopoulos first employed the term granular bainite to classify certain unconventional transformation products in continuously cooled steels, the term has been widely accepted and used, despite the lack of a clear consensus as to the detailed nature of the transformation products which constitute granular bainite. This paper presents the preliminary results of a TEM investigation of an 0.04 wt% C, copper-containing steel (designated HSLA-100). It is suggested that the term granular ferrite rather than granular bainite is a more accurate description of this multiphase reaction product.Figure 1 is a light micrograph of a sample which had been air-cooled from 900°C to room temperature. The microstructure is typical of that which has been termed granular bainite in the past and appears to consist of equiaxed ferritic grains together with other minor transformation products. In order to examine these structures in more detail, both continuously cooled and isothermally transformed and quenched materials have been examined with TEM. Granular bainite has been found in virtually all samples.

Arene Dearomatization via Radical Hydroarylation

2019 ◽  
Author(s):  
Autumn Flynn ◽  
Kelly McDaniel ◽  
Meredith Hughes ◽  
David Vogt ◽  
Nathan Jui
Keyword(s):  
Precious Metal ◽  
Room Temperature ◽  
Aryl Halide ◽  
Solvent System ◽  
Benzene Derivatives ◽  
Green Solvent ◽  
Photocatalytic System

A photocatalytic system for the dearomative hydroarylation of benzene derivatives has been developed. Using a combination of an organic photoredox catalyst and an amine reductant, this process operates through a reductive radical-polar crossover mechanism where aryl halide reduction triggers a regioselective cyclization event, giving rise to a range of complex spirocyclic cyclohexadienes. This light-driven protocol functions at room temperature in a green solvent system (aq. MeCN), without the need for precious metal-based catalysts or reagents, or the generation of stoichiometric metal byproducts.

One-pot Synthesis of Pyrazolone Sulfones by Iodine-catalyzed Sulfenylation of Pyrazolones with Aryl Sulfonyl Hydrazides Followed by Oxidation in Water

2018 ◽  
Vol 15 (3) ◽  
pp. 380-387
Author(s):  
Xia Zhao ◽  
Xiaoyu Lu ◽  
Lipeng Zhang ◽  
Tianjiao Li ◽  
Kui Lu
Keyword(s):  
Double Bond ◽  
Efficient Method ◽  
Room Temperature ◽  
Sulfonyl Chloride ◽  
Antibacterial Activities ◽  
Oxidation Reactions ◽  
Reaction Conditions ◽  
One Pot ◽  
X Ray ◽  
Amide Form

Aim and Objective: Pyrazolone sulfones have been reported to exhibit herbicidal and antibacterial activities. In spite of their good bioactivities, only a few methods have been developed to prepare pyrazolone sulfones. However, the substrate scope of these methods is limited. Moreover, the direct sulfonylation of pyrazolone by aryl sulfonyl chloride failed to give pyrazolone sulfones. Thus, developing a more efficient method to synthesize pyrazolone sulfones is very important. Materials and Method: Pyrazolone, aryl sulphonyl hydrazide, iodine, p-toluenesulphonic acid and water were mixed in a sealed tube, which was heated to 100°C for 12 hours. The mixture was cooled to 0°C and m-CPBA was added in batches. The mixture was allowed to stir for 30 min at room temperature. The crude product was purified by silica gel column chromatography to afford sulfuryl pyrazolone. Results: In all cases, the sulfenylation products were formed smoothly under the optimized reaction conditions, and were then oxidized to the corresponding sulfones in good yields by 3-chloroperoxybenzoic acid (m-CPBA) in water. Single crystal X-ray analysis of pyrazolone sulfone 4aa showed that the major tautomer of pyrazolone sulfones was the amide form instead of the enol form observed for pyrazolone thioethers. Moreover, the C=N double bond isomerized to form an α,β-unsaturated C=C double bond. Conclusion: An efficient method to synthesize pyrazolone thioethers by iodine-catalyzed sulfenylation of pyrazolones with aryl sulfonyl hydrazides in water was developed. Moreover, this method was employed to synthesize pyrazolone sulfones in one-pot by subsequent sulfenylation and oxidation reactions.

scholarly journals Lithium-mediated Ferration of Fluoroarenes

2020 ◽  
Vol 74 (11) ◽  
pp. 866-870
Author(s):  
Lewis C. H. Maddock ◽  
Alan Kennedy ◽  
Eva Hevia
Keyword(s):  
Hydrogen Atom ◽  
Organometallic Chemistry ◽  
Room Temperature ◽  
Structural Elucidation ◽  
Side Reactions ◽  
Metal Base ◽  
Lithium Amide ◽  
Mixed Metal ◽  
Important Challenge

While fluoroaryl fragments are ubiquitous in many pharmaceuticals, the deprotonation of fluoroarenes using organolithium bases constitutes an important challenge in polar organometallic chemistry. This has been widely attributed to the low stability of the in situ generated aryl lithium intermediates that even at –78 °C can undergo unwanted side reactions. Herein, pairing lithium amide LiHMDS (HMDS = N{SiMe3}2) with FeII(HMDS)2 enables the selective deprotonation at room temperature of pentafluorobenzene and 1,3,5-trifluorobenzene via the mixed-metal base [(dioxane)LiFe(HMDS)3] (1) (dioxane = 1,4-dioxane). Structural elucidation of the organometallic intermediates [(dioxane)Li(HMDS)2Fe(ArF)] (ArF = C6F5, 2; 1,3,5-F3-C6H2, 3) prior electrophilic interception demonstrates that these deprotonations are actually ferrations, with Fe occupying the position previously filled by a hydrogen atom. Notwithstanding, the presence of lithium is essential for the reactions to take place as Fe II (HMDS)2 on its own is completely inert towards the metallation of these substrates. Interestingly 2 and 3 are thermally stable and they do not undergo benzyne formation via LiF elimination.

Reactions of 4-Pyrones with Azomethine Ylides as a Chemo­selective Method for the Construction of Multisubstituted Pyrano[2,3-c]pyrrolidines

Synthesis ◽  
2021 ◽  
Author(s):  
Dmitrii L. Obydennov ◽  
Vyacheslav D. Steben’kov ◽  
Konstantin L. Obydennov ◽  
Sergey A. Usachev ◽  
Vladimir S. Moshkin ◽  
...  
Keyword(s):  
Double Bond ◽  
Ring Opening ◽  
Azomethine Ylides ◽  
Azomethine Ylide ◽  
Dipolar Cycloaddition ◽  
Computational Studies ◽  
Carbon Double Bond ◽  
Reactivity Indexes ◽  
Reaction Proceeds

Abstract4-Pyrones bearing electron-donating and electron-withdrawing groups react with nonstabilized azomethine ylides to form pyrano[2,3-c]pyrrolidines in moderate to good yields. The reaction proceeds chemoselectively as a 1,3-dipolar cycloaddition of the azomethine ylide at the carbon–carbon double bond of the pyrone activated by the electron-withdrawing substituent. The reactivity of 4-pyrones toward azomethine ylides was rationalized by computational studies with the use of reactivity indexes. The pyrano[2,3-c]pyrrolidine moiety could be modified, for example by a ring-opening transformation under the action of hydrazine to provide pyrazolyl-substituted pyrrolidines.

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