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  • 1
    Electronic Resource
    Electronic Resource
    Outer-sphere and inner-sphere processes in reductive elimination. Direct and indirect electrochemical reduction of vicinal dibromoalkanes (1990)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 112 (1990), S. 6162-6177 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00173a002
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  • 2
    Electronic Resource
    Electronic Resource
    Kinetics of the anodic dimerization of 4,4'-dimethoxystilbene by the rotating ring-disk electrode (1979)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 101 (1979), S. 7590-7593 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00519a020
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  • 3
    Electronic Resource
    Electronic Resource
    Enantioselective Cathodic Reduction of 4-Methylcoumarin: Dependence of Selectivity on Reaction Conditions and Investigation of the MechanismDedicated to Professor Dieter Seebach on the occasion of his 60th birthdayElectroorganic Synthesis, Part 64. Part 63: K. Möller, H. J. Schäfer, Electrochim. Acta 1997, 42, 1971-1978. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 2011-2024 
    Details
    ISSN: 0947-6539
    Keywords: enantioselective protonations ; kinetics ; quantum chemical calculations ; reductions ; voltammetry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cathodic reduction of 4-methylcoumarin (1) in acidic methanol/water in the presence of yohimbine leads to formation of a mixture of the hydrogenation product 4-methyl-3,4-dihydrocoumarin (2), with an enantiomeric excess (ee) of (R)-2 of 0-67%, and the hydrodimer 3. The relative yields of 2 and 3 and the ee of 2 depend on a number of experimental parameters such as pH, supporting electrolyte, working potential, and the concentrations of substrate and yohimbine, as demonstrated by a series of preparative-scale experiments. In addition, a series of voltammetric and kinetic measurements were carried out to investigate the influence of the individual experimental parameters. Three mechanistic possibilities have been examined, and by combination of the analytical data with the results of the preparative experiments, a single model is put forward which is in accord with the available results. The main features of the mechanistic model can be summarized as follows: 1) under acidic conditions (pH 2-3) the electroactive species is a complex between 1 and H3O+, the reduction of which leads to an enolic radical; 2) this radical is not reduced at the working potential but tautomerizes into the more easily reduced keto radical or dimerizes; 3) the keto radical is reduced and further protonated; 4) the function of the yohimbineH+ is to catalyze the tautomerization and enantioselectively protonate the final carbanion. Additionally, we conclude that the concentration of yohimbine in the immediate vicinity of the electrode is considerably higher than its stoichiometric concentration. Quantum chemical calculations demonstrate that si protonation of the intermediate anion by yohimbineH+ to give (R)-2 is energetically favored.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031216
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  • 4
    Electronic Resource
    Electronic Resource
    Regioselektive Funktionalisierung nicht aktivierter CH-Bindungen, 2. Photochemische Funktionalisierung des Myristoylrestes in 1,2-Alkandiyl- und o-Phenylen-1-(4-benzoylbenzoat)-2-myristaten (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 761-776 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Regioselective Functionalization of Non-Activated CH-Bonds, 2. Photochemical Functionalization of the Myristoyl Group in 1,2-Alkanediyl and o-Phenylene 1-(4-Benzoylbenzoate) 2-MyristatesMyristic acid (1a) was linked with ethylene glycol (2a), trans-1,2-cyclohexanediol (2b), and catechol (2c) to 4-benzoylbenzoic acid to form the diesters 4a-c. These cyclize by photolysis to the carbinols 12, which are converted into the methyl 7- to 13-oxomyristates (5a). The ketofunctionalization of the remote CH2-groups in 1a is more selective than in the corresponding benzoylbenzoic esters 13 without the 1,2-alkanediyl or o-phenylene link. Additionally the maximum of the functionalization is shifted from the end towards the middle of the chain. The latter observation can be explained by a higher population of gauche conformations at the beginning of the chain. In CCl4 the selectivity increases slightly from 4a to 4b, c with increasing rigidity of the link. The polarity of the solvent has only a small effect on the selectivity.
    Notes: Myristinsäure (1a) wurde über Ethylenglycol (2a), trans-1,2-Cyclohexandiol (2b) und Brenzcatechin (2c) mit 4-Benzoylbenzoesäure (3a) zu den Diestern 4a-c verklammert. Diese cyclisieren photolytisch zu den Carbinolen 12, die in die Methyl-7-bis-13-oxomyristate (5a) umgewandelt werden. Die erzielte Ketofunktionalisierung der entfernten CH2-Gruppen in 1a ist selektiver als bei vergleichbaren Benzoylbenzoesäureestern 13 ohne 1,2-Alkandiyl- bzw. o-Phenylen-Klammer. Zusätzlich verschiebt sich das Funktionalisierungsmaximum vom Kettenende zur Mitte. Letzteres läßt sich mit einer stärkeren Besetzung der gauche-Konformationen am Kettenbeginn deuten. Die Selektivität nimmt in CCl4 mit zunehmender Starrheit der Klammer von 4a nach 4b, c leicht zu. Die Solvenspolarität beeinflußt die Selektivität nur wenig.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160233
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  • 5
    Electronic Resource
    Electronic Resource
    Synthese von (Z)-7-Dodecenylacetat (Looplure) durch Kolbe-Elektrolyse (1977)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 110 (1977), S. 3544-3552 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of (Z)-7-Dodecenyl Acetate (Looplure) by Kolbe ElectrolysisButyrolactone yields with HBr and triphenylphosphine 3-carboxypropyl(triphenyl)phosphonium bromide (3). 3 forms with pentanal in a stereoselective Wittig reaction (Z)-4-nonenoic acid (4). 4 is coupled in a mixed Kolbe electrolysis with monomethyl glutarate (5a) to methyl (Z)-7-dodecenoate (7a). 7a is converted by LiAlH4-reduction and acetylation to (Z)-7-dodecenyl acetate (10) (looplure), the pheromone of Trichoplusia ni (cabbage looper). The 7a-yields in the mixed Kolbe electrolysis are influenced by the current density, the degree of neutralization, and especially the 4/5a-ratio.
    Notes: Aus Butyrolacton gewinnt man mit HBr und Triphenylphosphin 3-Carboxypropyl(triphenyl)-phosphonium-bromid (3), das mit Valeraldehyd in einer stereoselektiven Wittig-Reaktion (Z)-4-Nonensäure (4) liefert. 4 wird in einer gemischten Kolbe-Elektrolyse mit Glutarsäure-monomethylester (5a) zum (Z)-7-Dodecensäure-methylester (7a) gekuppelt. 7a ergibt durch LiAlH4-Reduktion und Acetylierung (Z)-7-Dodecenylacetat (10) (Looplure), das Pheromon von Trichoplusia ni (Cabbage looper). Die 7a-Ausbeute in der gemischten Kolbe-Elektrolyse wird durch die Stromdichte, den Neutralisationsgrad und besonders durch das 4/5a-Verhältnis beeinflußt.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19771101110
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  • 6
    Electronic Resource
    Electronic Resource
    Kolbe-Synthese ungesättigter Pheromone durch Coelektrolyse mit 5-Alkinsäuren (1980)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 113 (1980), S. 3898-3903 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Kolbe Synthesis of Unsaturated Pheromones by Coelectrolysis with 5-Alkynoic AcidsThe alkynoic acids 5a-g are synthesized by coelectrolysis of 5-alkynoic acids 2a-c with dicarboxylic monoesters 3a-d. By reduction, Lindlar-hydrogenation, and acetylation these are converted into pheromones such as (Z)-11-hexadecenyl acetate (7b), the pheromone of Mamestra brassicae. 2a-c can be prepared by alkynylation of 1-bromo-3-chloropropane to 1a-c, substitution by cyanide and hydrolysis.
    Notes: Durch Coelektrolyse der 5-Alkinsäuren 2a-c mit den Dicarbonsäure-monoestern 3a-d werden die Alkinsäuren 5a-g synthetisiert, die durch Reduktion, Lindlar-Hydrierung und Acetylierung in Pheromone wie (Z)-11-Hexadecenylacetat (7b), den Lockstoff der Kohleule Mamestra brassicae, übergeführt werden. 2a-c lassen sich durch Alkinylierung von 1-Brom-3-chlorpropan zu 1a-c, Cyanidsubstitution und Verseifung darstellen.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19801131221
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  • 7
    Electronic Resource
    Electronic Resource
    Selektive Blockierung von primären oder sekundären Hydroxylgruppen mit elektroaktiven Schutzgruppen (1981)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 946-958 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Selective Blocking of Primary or Secondary Hydroxyl Groups with Electroactive Protecting GroupsIn a diol such as 17, at first the primary OH-group is blocked with an electroactive protecting group (→ 18). Then the secondary OH-group is protected with a second group (→ 19), that is reduced at more negative potentials. Controlled potential electrolysis selectively deblocks the primary OH-group. As protecting groups the tritylone ( = 9,10-dihydro-10-oxo-9-phenyl-9-anthracenyl-) and 4-cyanobenzyl residue were suitable. With the help of a combination of these groups 1-dodecyloxy-3-octadecyloxy-2-propanol (27) was prepared starting with 1,2-O-isopropylideneglycerol (21).
    Notes: In Diolen wie 17 wird zunächst die primäre OH-Gruppe mit einer kathodisch abspaltbaren Schutzgruppen (→18), danach die sekundäre mit einer zweiten Gruppe geschützt (→ 19), die bei negativerem Potential abspaltbar ist. Potentiostatische Elektrolyse setzt nur die primäre Hydroxylgruppe frei. Als Schutzgruppen waren der Tritylon- (= 9,10-Dihydro-10-oxo-9-phenyl-9-anthracenyl-) und 4-Cyanbenzylrest geeignet. Mit Hilfe dieser Schutzgruppenkombination wurde 1-Dodecyloxy-3-octadecyloxy-2-propanol (27) ausgehend von 1,2-O-Isopropylidenglycerin (21) dargestellt.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19811140312
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  • 8
    Electronic Resource
    Electronic Resource
    Anodische Oxidation von Organoborverbindungen (1984)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1400-1423 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Anodic Oxidation of OrganoboranesOrganoboranes are converted into more easily oxidizable borates by reaction with nucleophiles and the alkyl groups are dimerized by anodic oxidation. The oxidation potentials (Ep) of the borates depend strongly on the nature of the complexing nucleophile, for instance Ep = +0.37V (vs. SCE) with OH- or +1.65V with tetrahydrofuran. The dimer yields are optimized with trioctylborane (5) by variation of the electrode material and the electrolyte. At the platinum anode in sodium hydroxide-methanol/tetrahydrofuran yields of 80% are obtained for acyclic alkyl groups, and lower ones for cycloalkyl groups. They exceed those obtained by the Kolbe electrolysis or the oxidation with neutral hydrogen peroxide and they are comparable to those of the AgNO3 oxidation. - The selective preparation of unsymmetrical products from borates with different alkyl groups is not possible, the dimerization proceeds likely via free radicals that couple statistically. Good yields of unsymmetrical coupling products are achieved, when one olefin is used in excess. With chloro-, ethoxy-, acetoxy-, and aryl-substituted alkyl groups the dimers are obtained in 21 - 66% yield, with bromide the yield are lower and with nitriles the dimerization fails.
    Notes: Organoborane werden durch Nucleophile in leichter oxidierbare Borate übergeführt und die Alkylreste durch anodische Oxidation dimerisiert. Die Oxidationspotentiale (Ep) der Borate werden stark vom komplexierenden Nucleophil beeinflußt, z. B. Ep = +0.37V (gKE) mit OH- oder + 1.65 V mit Tetrahydrofuran. Mit Trioctylboran (5) werden die Dimerenausbeuten (10) durch Variation von Elektrodenmaterial und Elektrolyt optimiert. An der Platinanode in KOH-Methanol/Tetrahydrofuran liegen die Ausbeuten für acyclische Alkylreste um 80%, die für Cycloalkane niedriger. Sie übertreffen die der Kolbe-Elektrolyse oder der Oxidation mit neutralem Wasserstoffperoxid und sind denen bei der Oxidation mit Silbernitrat vergleichbar. - Die selektive Darstellung unsymmetrischer Produkte aus Boraten mit unterschiedlichen Alkylresten gelingt nicht; die Dimerisierung verläuft wahrscheinlich über freie Radikale, die statistisch kuppeln. Gute Ausbeuten an unsymmetrischen Kupplungsprodukten werden jedoch erzielt, wenn ein Olefin im Überschuß eingesetzt wird. Mit chlor-, ether-, ester- und arylsubstituierten Alkylresten erhält man Dimere mit 21 - 66% Ausbeute. Mit Bromiden gelingt die Kupplung schlecht, mit Nitrilen überhaupt nicht.
    Additional Material: 12 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19841170412
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  • 9
    Electronic Resource
    Electronic Resource
    Anodische Hydroxylierung und Acetamidierung von konjugierten Dienen (1979)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 807-817 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Anodic Hydroxylation and Acetamidation of Conjugated DienesAnodic oxidation of 2,4-hexadiene (1), 1,3-butadiene (2), and 1,3-cyclohexadiene (3) in acetonitrile water/sodium perchlorate yields diols, 2-oxazolines, and 3-pyrrolines. Methyl sorbate (5) forms methyl 4,5-epoxy-(E)-2-hexenoate (26); 1,4-diphenyl-1,3-butadiene (4) is cleaved to benzaldehyde (24) and cinnamaldehyde (25). The product distribution is influenced by the supporting electrolyte. With tetrafluoroborate nearly exclusively diols are obtained, whilst in acetamide/acetonitrile 2-oxazolines and 3-pyrrolines are formed. As intermediates radical cations (31) are assumed.
    Notes: Die anodische Oxidation von 2,4-Hexadien (1), 1,3-Butadien (2) und 1,3-Cyclohexadien (3) in Acetonitril/Wasser/Natriumperchlorat führt zu einem Gemisch aus Diolen, 2-Oxazolinen und 3-Pyrrolinen. Sorbinsäure-methylester (5) liefert 4,5-Epoxy-(E)-2-hexensäure-methylester (26); 1,4-Diphenyl-1,3-butadien (4) wird zu Benzaldehyd (24) und Zimtaldehyd (25) gespalten. Die Produktverhältnisse werden vom Leitsalz beeinflußt. In Gegenwart von Tetrafluoroborat entstehen nahezu ausschließlich Diole, während die Elektrolyse in Acetamid/Acetonitril zu 2-Oxazolinen und 3-Pyrrolinen führt. Als Zwischenprodukte werden Radikalkationen (31) angenommen.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19791120305
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  • 10
    Electronic Resource
    Electronic Resource
    Elektrochemische Reduktion und Oxidation von Allenen (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 960-969 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Electrochemical Reduction and Oxidation of AllenesThe allenes 1-3 are reduced on mercury at -2.17 V (sce) (1), -3.12 V (2), and below -3.30 V (3); they are oxidized on glassy carbon at 1.25, 1.65 V (1), 1.75 V (2), and above 2.25 V (3). In the preparative reduction 1 forms, depending on the workup, 86% of 1,1,3,3-tetraphenyl-1-propene (6a) or up to 50% of aldehyde 9, a formylation product of the rearranged radical anion intermediate; on carboxylation of the electrolyte 54% of carboxylic acid 8 are formed. The allene 2 is hydrogenated to give 30% of (E)-1-phenyl-1-propene (10) and hydrodimerized to form 30% of 2,3-dimethyl-1,4-diphenylbutane (11). 3 is nearly inert to reduction. The anodic oxidation of 1 yields in methylene dichloride/methanol 61-73% of 2-chloro-1,1,3-triphenylindene (13), which is probably formed by chlorine, that is electrochemically generated from methylene chloride. In methanol/dioxane 13 is not obtained but 71% of indanone 16 are produced. The oxidation of 2 and 3 is unselective; due to follow-up oxidations many products are formed in low yield.
    Notes: Die Allene 1-3 werden bei -2.17 V (gKE) (1), -3.12 V (2) und kathodischer als -3.30 V (3) an Quecksilber reduziert; an Glaskohlenstoff werden sie bei 1.25, 1.65 V (1), 1.75 V (2) und über 2.25 V (3) oxidiert.  -  Bei der präparativen Reduktion entstehen aus 1, je nach Aufarbeitung, 86% 1,1,3,3-Tetraphenyl-1-propen (6a) oder bis 50% des Aldehyds 9, ein Formylierungsprodukt des umgelagerten Radikalanions; beim Carboxylieren des Elektrolyten bilden sich 54% der Carbonsäure 8. Das Allen 2 wird zu 30% (E)-1-Phenyl-1-propen (10) hydriert und zu 30 % 2,3-Dimethyl-1,4-diphenylbutan (11) hydrodimerisiert. 3 läßt sich kaum noch reduzieren. Die anodische Oxidation von 1 führt in Methylenchlorid/Methanol zu 61-73% 2-Chlor-1,1,3-triphenylinden (13), dessen Bildung vermutlich Chlor bewirkt, das elektrochemisch aus Methylenchlorid erzeugt wird. In Methanol/Dioxan entsteht kein 13, sondern 71% des Indanons 16. Die Oxidation von 2 und 3 verläuft unselektiv; durch Folgeoxidationen bilden sich zahlreiche Produkte in niedriger Ausbeute.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160313
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