scholarly journals Photochemische Reaktionen von Übergangsmetall-Olefin-Komplexen, V [1]. Die Umsetzung von Tricarbonyl-η-6.6-dimethylfulven-chrom(0) mit 7-Methyl- und 7-Methoxycycloheptatrien / Photochemical Reactions of Transition Metal Olefin Complexes, V [1]. The Reactions of Tricarbonyl-η-6,6-dimethylfulvene-chromium(0) with 7-Methyl- and 7-Methoxycycloheptatriene

1982 ◽  
Vol 37 (10) ◽  
pp. 1322-1326 ◽  
Author(s):  
Cornelius G. Kreiter ◽  
Hans Kurz
Keyword(s):  
Nmr Spectroscopy ◽  
Transition Metal ◽  
Column Chromatography ◽  
Room Temperature ◽  
Photochemical Reactions ◽  
Membered Ring ◽  
Reaction Products ◽  
Methyl Group

Abstract The stereochemistry of the photo reaction products of tricarbonyl-η-6,6-dimethyl-fulvene-chromium(O) (1) with 7-methyl-and 7-methoxycycloheptatriene was studied by NMR-spectroscopy. Both trienes add to 1, displace a CO ligand, and form substituted dicarbonyl-η3-2-cycloheptadienylene-η5-2-cyclopentadienylidene-propane-chromium(0) complexes. With C7H7CH3 only one isomer (3) is formed with the methyl-group in endo-position and the enyl system encompassing C(1′)-C(3′) of the seven membered ring. C7H7OCH3 yields 3 isomers which were separated by column chromatography. 5 has the same constitution as 3. The isomers 4 and 5 bear the OCH3-group in e^o-position. The enyl system of 4 is located on C(1′)-C(3′), that of 6 on C(3′)-C(5′). 6 rearranges at room temperature to 4.

Das dynamische Verhalten des 1-Methyl-1-benzothiepinium-Ringsystems/The Dynamic Behaviour of the 1-Methyl-1-benzothiepinium Ring System

1981 ◽  
Vol 36 (8) ◽  
pp. 974-977 ◽  
Author(s):  
Hans Hofmann ◽  
Franz Dickert
Keyword(s):  
Nmr Spectroscopy ◽  
Room Temperature ◽  
Dynamic Behaviour ◽  
Ring System ◽  
Membered Ring ◽  
Ring Inversion ◽  
Methyl Group ◽  
H Nmr ◽  
Pyramidal Inversion ◽  
Mutual Conversion

Abstract By 1H NMR spectroscopy the stereochemistry of the 1-methyl-1-benzothiepinium ring system was investigated both in thermodynamic and kinetic respects. It was shown that in solution a rapid mutual conversion of the boat shaped seven membered ring system with exo-respectively endo-S-methyl group occurs via a ring inversion and not by a pyramidal inversion at the sulfonium ion. At room temperature predominantly the conformation with the exo-S-methyl group is present.

Photochemische Reaktionen von Übergangsmetall-Olefin-Komplexen, VII [1] Die Reaktion von Triearbonyl-η6-cyclooctatetraen-chrom(0) mit 6-mono-und 6.6-disubstituierten Fulvenen / Photochemical Reactions of Transition Metal Olefin Complexes, VII [1] The Reactions of Tricarbonyl-η6-cyclooctatetraene-chromium(0) with 6-Mono-and 6,6-Disubstituted Fulvenes

1983 ◽  
Vol 38 (7) ◽  
pp. 841-848 ◽  
Author(s):  
Cornelius G. Kreiter ◽  
Hans Kurz
Keyword(s):  
Nmr Spectroscopy ◽  
Transition Metal ◽  
Photochemical Reactions ◽  
Membered Ring ◽  
Fold Axis ◽  
Chromium Complexes ◽  
Hindered Rotation ◽  
Ir And Nmr Spectroscopy ◽  
Oxidative Rearrangement ◽  
Rearrangement Reaction

Tricarbonyl-η6-cyclooctatetraene-chromium(0) (1) reacts photochemically with 6-mono- and 6,6-disubstituted fulvenes (2-7) in a substitution-oxidative rearrangement-reaction to dicarbonyl-η-1′-3':1″-5″-(cycloocta-2′,4′,6′-trien-1′,8′-ylene-cyclopentadienylidene-methane)chromium complexes (8−13). Tricarbonyl-η-6,6-dimethylfulvene-chromium(0) (16) reacts with cyclooctatetraene, bicyclo[6,1,0]nona-2,4,6-triene and anti-9-methoxybicyclo-[6,1,0]nona-2,4,6-triene in a similar manner and forms 8 and 2-bicyclo[6,1,0]nona-4′,6′-dien-2′,3′-ylene-2-cyclopentadienylidene-propane complexes (19, 20). In addition to 13 6-dimethylaminofulvene (7) yields with 1 dicarbonyl-η-1′,6′,7′: 1″-5″-(2-cyclohepta-2′,4′,6′-trien-7′-ylidene-1 -cyclopentadienylidene-1-dimethylamino-ethane)-chromium (14) which involves an unexpected contraction of the eight-membered ring. The constitutions of 8−15 and 19−20 were determined by IR and NMR spectroscopy.In Cr(CO)2[C(C6H5)2(C5H4)(C8H8)] (9) one of the phenyl groups shows hindered rotation around its two fold axis.

scholarly journals Superelectrophilic activation of 5-hydroxymethylfurfural and 2,5-diformylfuran: organic synthesis based on biomass-derived products

2016 ◽  
Vol 12 ◽  
pp. 2125-2135 ◽  
Author(s):  
Dmitry S Ryabukhin ◽  
Dmitry N Zakusilo ◽  
Mikhail O Kompanets ◽  
Anton A.Tarakanov ◽  
Irina A Boyarskaya ◽  
...  
Keyword(s):  
High Pressure ◽  
Nmr Spectroscopy ◽  
Dft Calculations ◽  
Organic Synthesis ◽  
Room Temperature ◽  
Trifluoromethanesulfonic Acid ◽  
Reaction Products ◽  
Triflic Acid ◽  
Pressure Tubes ◽  
Acidic Zeolites

The reaction of 5-hydroxymethylfurfural (5-HMF) with arenes in superacidic trifluoromethanesulfonic acid (triflic acid, TfOH) as the solvent at room temperature for 1–24 h gives rise to 5-arylmethylfurfurals (yields of 17–91%) and 2-arylmethyl-5-(diarylmethyl)furans (yields of 10–37%). The formation of these two types of reaction products depends on the nucleophilicity of the arene. The same reactions under the action of acidic zeolites H-USY in high pressure tubes at 130 °C for 1 h result in the formation of only 5-arylmethylfurfurals (yields of 45–79%). 2,5-Diformylfuran (2,5-DFF) in the reaction with arenes under the action of AlBr3 at room temperature for 1 h leads to 5-(diarylmethyl)furfurals (yields of 51–90%). The reactive protonated species of 5-HMF and 2,5-DFF were characterized by NMR spectroscopy in TfOH and studied by DFT calculations. These reactions show possibilities of organic synthesis based on biomass-derived 5-HMF and 2,5-DFF.

scholarly journals Photochemische Reaktionen von Übergangsmetall-Organyl-Komplexen mit Olefnen, VI. Reaktionen von Tricarbonyl-η5-2,4-cyclohexadienyl-mangan mit konjugierten Dienen / Photochemical Reactions of Transition Metal Organyl Complexes with Olefins, VI. Reactions of Tricarbonyl (η5-2,4-cyclohexadienyl)manganese with Conjugated Dienes

1991 ◽  
Vol 46 (10) ◽  
pp. 1377-1383 ◽  
Author(s):  
Cornelius G. Kreiter ◽  
Klaus Lehr
Keyword(s):  
Nmr Spectroscopy ◽  
Transition Metal ◽  
Bond Formation ◽  
Conjugated Dienes ◽  
Photochemical Reactions ◽  
Ir And Nmr Spectroscopy ◽  
Different Types

Tricarbonyl-η5-2,4-cyclohexadien-1-yl-manganese (1) was reacted photochemically at 253 K with simple conjugated dienes. Four different types of products were obtained, depending upon the dienes. With 1,3-butadiene (A) dicarbonyl-η4:3-1-(3-buten-1,2-diyl)-2,4-cyclohexadiene-manganese (2A) is isolated. 2-Methyl-1,3-butadiene (B) yields the methyl-substituted diastereomeric dicarbonyls 2B, 2B′, the [4+5]-cycloadduct tricarbonyl-η3:2-3-methyl-bicyclo-[4.3.1]-3,8-decadien-7-yl-manganese (3B) and tetracarbonyl-η3-4-methylene-bicyclo[4.3.1]-8-decen-3-yl-manganese (4B) with an exocyclically coordinated tetracarbonylmanganese fragment. With 2,3-dimethyl-1,3-butadiene (C) only the [4+5]-cycloadduct 3C and the tetracarbonyl 4C are obtained. No CC-bond formation is observed with E,E-2,4-hexadiene (D) and 1,3-cyclohexadiene (E). Carbonyl-η5-2,4-cyclohexadien-1 -yl-η4-E,E-2,4-hexadiene-manganese (5D), and carbonyl-η4-1,3-cyclohexadiene-η5-2,4-cyclohexadien-1-yl-manganese (5E) are the only products. The complexes were separated and purified by HPL chromatography. Their constitutions were determined by IR and NMR spectroscopy.

scholarly journals Diastereoselective intramolecular Diels–Alder reactions of the furan diene: the synthesis of (±)-1,4-epoxycadinane

1993 ◽  
Vol 71 (5) ◽  
pp. 611-622 ◽  
Author(s):  
Christine Rogers ◽  
Brian A. Keay
Keyword(s):  
Room Temperature ◽  
Furan Ring ◽  
Methylene Chloride ◽  
Membered Ring ◽  
Diels Alder ◽  
Methyl Group ◽  
Oxygen Bridge ◽  
Catalytic Quantity ◽  
The One

The diastereoselective intramolecular Diels–Alder reactions of the furan diene (IMDAF), in which the side arm comprises four carbon atoms and is substituted by a methyl group adjacent to, or one carbon removed from, the furan ring, are described. Adducts are formed in moderate to excellent yields when treated with either Florisil in methylene chloride at room temperature or methylaluminum dichloride in methylene chloride at −78 °C. Florisil is most effective for substrates containing unsubstituted dienophiles. An equimolar quantity (1.1 equivalents) of methylaluminum dichloride is most effective for precursors having methacrolein-type dienophiles, while a catalytic quantity (0.1 equivalent) is effective for crotonaldehyde-type dienophiles. Only the adducts with the side arm orientated syn with respect to the oxygen bridge are detected and isolated. The major diastereomer is the one in which the methyl group (initially on the side arm) is situated equatorially on the newly formed six-membered ring. An application of the diastereoselective IMDAF reaction to the synthesis of (±)-1,4-epoxycadinane is described, beginning with 2-methylfuran.

Konformation konjugierter Cyclopropanderivate mit sterischer Hinderung / The Confirmation of Cyclopropane Derivatives with a Rotation Barrier

1980 ◽  
Vol 35 (1) ◽  
pp. 129-136 ◽  
Author(s):  
Rajiha I. Al-Nia'mi ◽  
Muthana Shanshal
Keyword(s):  
Low Temperature ◽  
Aromatic Ring ◽  
Room Temperature ◽  
Membered Ring ◽  
Rotation Barrier ◽  
Stable Conformation ◽  
Methyl Group ◽  
Planar Conformation ◽  
Pmr Spectra ◽  
Cyclopropane Derivatives

Abstract The influence of α- and o-methyl substituents on the conformation of phenylcyclopropane is studied. Synthesis as well as low temperature PMR studies of the corresponding derivatives are carried out. The changes in the PMR spectra measured at room temperature and -100 °C are too small to count for the rotation barrier calculations. Fo 2,2-dichloro-1-phenyl-cyclopropane (8) ,2,2-dichloro-1-methyl-1-phenyl-cyclopropane (9) and 2,2-dichloro-1-o-tolyl-cyclopropane(10) the predicted most stable conformation is the near-bisected in which the aromatic ring is slightly twisted towards the CI atoms. For 2,2-dichloro-1-(2,6-dimethyl-phenyl)-cyclopropane (11) the planar conformation is predicted to be most stable. MINDO/3-FORCES calculations of the conformations and rotation barriers of similarly methylsubstituted vinyl-cyclopropanes, phenylcyclopropane and 2-cyclopropyl-pyridine are reported. It is found that introducing a methyl group to the a-position of the three membered ring or to the C4 atom f the vinylgroup causes the deviation of the olefine plane from the bisected conformation by 30°. Similar deviations are expected for the α-and o-methyl-phenylcyclopropanes.

A Reinvestigation of the Deceptively Simple Reaction of Toluene with ●OH, and the Fate of the Benzyl Radical. I. a Combined Thermodynamic and Kinetic Study on the Competition Between ●OH Addition and Hydrogen Abstraction Reactions.

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Marc E. Segovia ◽  
Martina Kieninger ◽  
Oscar Ventura ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Hydrogen Abstraction ◽  
Reaction Rates ◽  
Composite Model ◽  
Alternative Mechanism ◽  
Radical Intermediate ◽  
Experimental Conditions ◽  
Methyl Group ◽  
Benzyl Radical

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

A Reinvestigation of the Deceptively Simple Reaction of Toluene with ●OH, and the Fate of the Benzyl Radical. I. a Combined Thermodynamic and Kinetic Study on the Competition Between ●OH Addition and Hydrogen Abstraction Reactions.

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Marc E. Segovia ◽  
Martina Kieninger ◽  
Oscar Ventura ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Hydrogen Abstraction ◽  
Reaction Rates ◽  
Composite Model ◽  
Alternative Mechanism ◽  
Radical Intermediate ◽  
Experimental Conditions ◽  
Methyl Group ◽  
Benzyl Radical

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

Decomposition of peroxobenzoic acid in benzene catalyzed by transition metal 2,4-pentanedionates

1984 ◽  
Vol 49 (3) ◽  
pp. 673-679 ◽  
Author(s):  
Pavel Lederer ◽  
Eva Mácová ◽  
Josef Vepřek-Šiška
Keyword(s):  
Transition Metal ◽  
Reaction Rate ◽  
Reaction Products ◽  
Acid Decomposition ◽  
Analogous Experiment ◽  
Catalytic Effects

The decomposition of peroxobenzoic acid in benzene was studied, and catalytic effects of Fe(III), Mn(III), Co(II), Co(III), and Cr(III) on the reaction rate and the composition of the reaction mixture were investigated. An analogous experiment carried out in perdeuterobenzene and determination of the distribution of deuterium in the reaction products provided evidence for the participation of the solvent in peroxobenzoic acid decomposition.

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