Carbanions phosphonate préparés par voie électrochimique: formation et réactivité vis-à-vis d'un aldéhyde

1989 ◽  
Vol 67 (8) ◽  
pp. 1332-1343 ◽  
Author(s):  
Jean-Christophe Le Menn ◽  
Jean Sarrazin ◽  
André Tallec
Keyword(s):  
General Formula ◽  
Carbonyl Group ◽  
Darzens Reaction ◽  
Phosphonate Group ◽  
Mercury Cathode ◽  
Diethyl Phosphate ◽  
Electron Reduction ◽  
Chloride Elimination ◽  
Selection Of

Reactivity towards p-methoxybenzaldehyde (ArCHO) of electrochemically generated phosphonate carbanions has been investigated. Electrolyses were carried out at a mercury cathode in DMF and two routes to the desired carbanion have been compared: (i) Deprotonation of phosphonates of general formula (EtO)2P(O)CHYW (Y = W = Cl; Y = H, W = Cl; Y = Cl, W = CO2Et; Y = H, W = CO2Et; Y = CH3, W = CO2Et; Y = Cl, W = CH3), by the bases resulting from the electroreduction of azobenzene; addition of the carbanion formed onto the carbonyl group takes place and leads to the adduct (EtO)2P(O)CYW(Ar)O−. (ii) Two-electron reduction of halophosphonates (EtO)2P(O)CXYW (X = Cl, Y and W as above; X = Br, W = CO2Et, Y = Cl, Br, or CH3); when no H atom is present on the carbon bearing the phosphonate group (Y and W ≠ H), the same evolution leading to the above adduct is observed; on the contrary, when Y = H, the electrogenerated carbanion deprotonates the substrate and the resulting carbanion [Formula: see text] reacts with the aldehyde, giving the adduct(EtO)2P(O)CXW(Ar)O−.Evolution of the intermediate adduct depends on the substituants Y (or X) and W: when W = CO2Et, whatever the nature of Y (or X), diethyl phosphate is eliminated with formation of the ethylenic ArCH = CWY (or X) (Wittig–Horner reaction); the same evolution is observed when Y = W = Cl. When W = Cl and Y = H or CH3, the final product is the phosphonate epoxyde resulting from chloride elimination (Darzens reaction).Chemo- and stereoselectivity depend only on the nature of Y and W but are independent of the mode of generation of the carbanion. Yields are limited by side-protonation reactions, which are related to the basicity of the phosphonate carbanions. Analysis of the results permits selection of the optimal electrolysis conditions for purposes of synthesis. Keywords: electrosynthesis, electrogenerated bases, phosphonates, Wittig–Horner.

Selection of the Measuring Teeth Number of Involute Cylindrical Gear Common Normal

2012 ◽  
Vol 479-481 ◽  
pp. 908-912
Author(s):  
Quan Chao Yang ◽  
Zhi Liang Qian ◽  
Yan Jun Gu
Keyword(s):  
General Formula ◽  
Cylindrical Gear ◽  
Normal Length ◽  
Best Value ◽  
The Common ◽  
Selection Of

Focus on the inconvenient inquiring of non-standard gears common normal length and irrational selection of the measuring teeth number, the computational general formula of common normal length and measuring teeth number is educed. According to best value method, the scope of measuring teeth number is ascertained. A rational measuring teeth number is selected on the basis of the scope. According to Matlab-GUI, design a software which can calculate the common normal length and measuring teeth number of involute cylindrical gear. The result shows that the solving of measuring teeth number by best value method is more reasonable and the calculation of common normal length is exacter and swifter by the software.

Die Reduktion von Triphenylphosphan-Derivaten zu ihren Radikalanionen und zum Dibenzophosphol-Radikaldianion [1] / The Reduction of Triphenylphosphane Derivatives to their Radical Anions and to the Radical Dianion of Dibenzophosphole [1]

1982 ◽  
Vol 37 (11) ◽  
pp. 1382-1387 ◽  
Author(s):  
Wolfgang Kaim ◽  
Peter Hänel ◽  
Hans Bock
Keyword(s):  
Low Temperature ◽  
Alkali Metal ◽  
Ring Closure ◽  
Metal Reduction ◽  
Paramagnetic Species ◽  
Radical Anions ◽  
Spin Distribution ◽  
Pyramidal Geometry ◽  
Mercury Cathode ◽  
Electron Reduction

Triphenylphosphane 1, its oxide 2 and sulfide 3 undergo one-electron reduction at a mercury cathode in DMF to yield the corresponding radical anions. ESE analysis of the paramagnetic species is facilitated by deuteration and suggests a pyramidal geometry of the radicals. Reduction with potassium metal in DME at low temperature yields also radical anions for 2 and 3. The phosphane 1, however, reacts under phenyl cleavage and potassiumphenyl-assisted ring closure to the dianion of 5H-dibenzophosphole 4. This radical 4· ⊖⊖ is also obtainod by alkali metal reduction of P-phenyldibenzophosphole o, and its spin distribution is compared to iso-.-π-electronic radicals containing CH, N, O, S, or Se links instead of the phosphorus atom.

Electron impact studies. XCVIII. Negative ion mass spectra of the carbonyl group. The Aryl-CO- and Aryl-COCO- systems

1975 ◽  
Vol 28 (10) ◽  
pp. 2169 ◽  
Author(s):  
JH Bowie ◽  
S Janposri
Keyword(s):  
Nitro Group ◽  
Electron Impact ◽  
General Formula ◽  
Carbonyl Group ◽  
Mass Spectra ◽  
Negative Ion ◽  
Aryl Group ◽  
Impact Studies ◽  
Molecular Anions

Collision-induced decompositions of molecular anions of the general formula aryl-CO-alkyl yield aryl- ions. The aryl-CO-aryl group is stable under these conditions. Parent anions from α-dicarbonyl systems do not generally fragment but, in the case of o-nitrobenzil, fragment anions are produced after cyclization of the nitro group at both carbonyl centres.

Zur Reaktion aromatischer Phosphanderivate mit Elektronen, I. / On the Reaction of Aromatic Phosphane Derivatives with Electrons, I.

1981 ◽  
Vol 36 (2) ◽  
pp. 150-156 ◽  
Author(s):  
Wolfgang Kaim
Keyword(s):  
Radical Anions ◽  
Solvated Electrons ◽  
Mercury Cathode ◽  
Electron Reduction

Abstract The compounds ;p-Me2P(X)-C6H4-P(X)Me2, X = O, S, Se, NPh undergo one-electron reduction at a mercury cathode or on reaction with solvated electrons in a K/18-crown-6/THF mixture. The radical anions formed are persistent and have been characterized by ESR. They may be described as complexes of the spin-bearing moiety p-Me2P-C6H4-PMe2 · with the coordinated groups X.

β Elimination of a phosphonate group from an alkoxyl radical — Intramolecular acylation using acylphosphonate derivatives as carbonyl group acceptors

2005 ◽  
Vol 83 (6-7) ◽  
pp. 917-921 ◽  
Author(s):  
Chang Ho Cho ◽  
Sunggak Kim
Keyword(s):  
Carbonyl Group ◽  
Direct Reduction ◽  
Catalytic Amount ◽  
Radical Cyclization ◽  
Alkoxyl Radical ◽  
Phosphonate Group ◽  
Radical Acceptor ◽  
Ready Access ◽  
First Time ◽  
Cyclohexanone Derivative

The possibility of β elimination of a phosphonate group in radical reactions was studied. The facile β elimination of the phosphonate group from an alkoxyl radical was observed for the first time, whereas the β elimination of the phosphonate group from an aminyl and an alkyl radical did not occur. On the basis of our findings, the use of an acylphosphonate as a carbonyl group radical acceptor was investigated. Radical cyclization of the acylphosphonate in the presence of hexamethylditin in benzene at 300 nm for 2 h gave a cyclopentanone or a cyclohexanone derivative in good yield without the formation of a direct reduction product. The reaction can be carried out in the presence of a catalytic amount of hexamethylditin (0.2 equiv.) under similar conditions. In addition, an alkyl phosphonothiolformate group can act as an alkylthiocarbonyl group equivalent radical acceptor, providing ready access to a thiolactone synthesis.Key words: radical, β elimination, acylation, cyclization, acylphosphonate.

The electrochemistry and the kinetics of the formation of ruthenium(II) nitrogen complexes

1968 ◽  
Vol 46 (16) ◽  
pp. 2743-2747 ◽  
Author(s):  
I. J. Itzkovitch ◽  
John A. Page
Keyword(s):  
Mercury Electrode ◽  
Reduction Wave ◽  
Base Electrolyte ◽  
Mercury Cathode ◽  
Standard Calomel Electrode ◽  
Oxidation Wave ◽  
Dropping Mercury Electrode ◽  
Aqueous Base ◽  
Electron Reduction ◽  
Ar Gas

Electrolysis at a mercury cathode controlled at −0.50 V (vs. standard calomel electrode s.c.e.) in a H2SO4–K2SO4 electrolyte with pH of 2.6 and saturated with Ar gas has been used to prepare RuII–(NH3)5X. The reaction of this species with N2 in the aqueous base electrolyte at 26 °C has been studied and found to follow the equations:[Formula: see text]In base electrolyte saturated with N2 at 1 atm (CN2 ≈ 6 × 10−4 M) the value of the apparent first order constant, k′m is 4.4 × 10−5 s−1 and the value of kd is 4.2 × 10−2 1 mole−1 s−1.The electrochemistry of the various ruthenium species was also investigated in the H2SO4–K2SO4 electrolyte. At the dropping mercury electrode, RuIII (NH3)5Cl gave a well-defined one electron reduction wave with E1/2 = −0.27 V; RuII (NH3)5X gave a well-defined one electron oxidation wave with E1/2 = −0.25 V. The nitrogen complexes gave oxidation waves at a rotating platinum microelectrode, the monomer with E1/2 = +0.72 V and the dimer with E1/2 = +0.78 V.

4,5-Dihydro-4,5-dihydroxyimidazoles as products of the reduction of 2-nitroimidazoles. HPLC assay and demonstration of equilibrium transfer of glyoxal to guanine

1989 ◽  
Vol 67 (12) ◽  
pp. 2128-2135 ◽  
Author(s):  
Rick Panicucci ◽  
Robert A. McClelland
Keyword(s):  
Electrochemical Reduction ◽  
Hplc Analysis ◽  
Chemical Reduction ◽  
Authentic Sample ◽  
Hplc Method ◽  
Radiation Chemical ◽  
Mercury Cathode ◽  
Guanine Derivatives ◽  
Electron Reduction ◽  
Quantitative Hplc Analysis

An HPLC method has been employed to study the electrochemical reduction (mercury cathode at −800 mV with respect to calomel electrode) of the 2-nitroimidazole benznidazole (N′-benzyl-(2′-nitro-1′-imidazoyl)acetamide). The principal product of this reduction is the cyclic guanidinium ion 3c (protonated N′-benzyl-(2′-amino-4′,5′-dihydro-4′,5′-dihydroxy-1-imidazoyl)acetamide), which forms in a linear fashion as the nitroimidazole is reduced and accounts for 75% of the product upon completion of the reduction. To perform the HPLC analysis quantitatively an authentic sample of this product (isolated as cis-trans isomers) was prepared as the sulfate salt through the reaction of N-benzyl-2-guanidinoacetamide sulfate with aqueous glyoxal. The two isomers of 3c arise through the nonreductive decomposition of the 2-hydroxylaminoimidazole, which is the product of a four-electron reduction of the nitroimidazole. Analysis of high field 1H NMR spectra also showed that the two isomers of 3c were the principal products following electrochemical reduction, neutral aqueous zinc reduction, and radiation chemical reduction. Previous investigations using NMR of the reductions of misonidazole (3-methoxy-1-(2′-nitro-1′-imidazoyl)-2-propanol) and 1-methyl-2-nitroimidazole have shown that the corresponding dihydroimidazoles 3a and 3b are the major products. The agreement of these various NMR and HPLC results suggests that the formation of dihydroimidazoles 3 is a general phenomenon for model reductions of 2-nitroimidazoles in neutral aqueous solution. Previous workers have shown that 2-nitroimidazole reduction mixtures, when treated with guanine derivatives, form the adduct 4 derived from the guanine and glyoxal. This work demonstrates that this adduct is also formed when authentic samples of 3a, 3b, and 3c are reacted with 2′-deoxyguanosine. A quantitative HPLC analysis, however, demonstrates that the reaction does not proceed to completion, and in fact the equilibrium for formation of 4 is unfavorable. This suggests that guanines are not useful derivatizing agents for the quantitative assay of "glyoxal-like" products formed in chemical or biological reductions of 2-nitroimidazoles. Keywords: nitroimidazole, reduction of nitroimidazoles, glyoxal from nitroimidazoles.

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