Reactions of 1,2-dichloro-3,3-difluorocyclopropene with methanolic sodium methoxide

Slow addition of sodium methoxide in methanol to 1,2-dichloro-3,3-difluorocyclopropene yields initially 1-chloro-2-methoxy-3,3-difluorocyclopropene. Further addition of methoxide in methanol yields preferentially Z 1-chloro-2-fluoro-3,3,3-trimethoxypropene and a small amount of dimethyl malonate. The ortho ester undergoes facile hydrolysis during the reaction and work up to form the acrylate ester, Z methyl 2-fluoro-3-chloroacrylate. A mechanism is suggested to account for the selective isomer formation.     

Reaction of tris(trimethylsilyl)methylsilicon halides with methanolic sodium methoxide. Probability of sila-olefin intermediates

The compounds TsiSiR₂X [Tsi = Me₃Si)₃C; R = Me, X = Cl, Br, I, or R = Ph, X = F, Cl, Br, I)] react with boiling 2 M MeONa-MeOH to give products of the type (Me₃Si)₂CHSiR₂OMe. It is suggested that the reaction proceeds through an elimination, analogous to E2 eliminations of alkyl halides, involving synchronous attack of MeO^? at an Me₃Si group, liberation of X^?, and formation of (Me₃Si)₂CSiR₂. The compounds TsiSiPhMeF TsiSiPhCl₂ react analogously to give (Me₃Si)₂CHSiPhMe(OMe) and (Me₃Si)₂CHSiPh(OMe)₂ [tha latter presumably by solvolysis of the initially-formed (Me₃Si)₂CHSiPhCl(OMe)]. The compounds TsiSiMe₂OMe and TsiSiMe₃ do not react, while TsiSiMe₂H gives TsiH. The compound TsiSiCl₃ reacts with 0.1 M MeONa-MeOH to give the substitution and elmination products TsiSiCl₂(OMe) and (Me₃Si)₂CHSi(OMe)₃ in ca. $\text{1}\text{2}$ ratio.     

Formation of isoindole derivatives by reaction of phthalonitrile with sodium methoxide

It is shown by means of IR spectra that the reaction of phthalonitrile with sodium methoxide in benzene in the presence of traces of water or methanol proceeds via a series-parallel mechanism in two steps to give cyclic products. The proposed structure of the intermediate is an oligomeric isbindolenine chain with terminal NNa and OCH₃ groups. The final product is the sodium salt of monomethoxyiminoisoindolenine. The analogous reaction in methanol proceeds at a higher rate that makes it impossible to isolate or detect the intermediate; the final product is 1,1-dimethoxy-3-iminoisoindoline.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 63–68., January, 1977.     

Stereochemistry at tin and mechanism of three cleavage reactions of carbontin bonds

The cleavages of the trityltin bond by NaFe(CO)₂Cp, LiBHEt₃ and Ph₃-SnLi are not stereoselective. This is explained in terms of a one-electron transfer mechanism leading to a triorganostannyl radical which can undergo inversion before reacting with another radical to give the product.     

Stereochemistry and mechanism of the copper(I) halide cleavage of thallium-carbon bonds

Stereochemical studies on the copper(I) halide cleavage of thallium-carbon bonds in acetonitrile indicate that at 80°C a radical path accounts for approximately $\text{2}\text{3}$ of the product, whereas at 60°C an ionic path predominates. The results are consistent with e.s.r. measurements by a spin trapping technique.     

Abnormal nucleophilic substitution of 3-trichloromethylpyridines by methoxide

3-Trichloromethylpyridine and its α-chlorinated derivatives behave as ambident electrophilic substrates towards methoxide which attacks an α-position and the trichloromethyl group.     

Reductive cleavage of dichalcogenide bonds

Electrochemical reduction of 1,2-di(2,4,6-triphenylpyridinium-l)ethane, 1,4-di(2,4,6-triphenylpyridinium-1)butane, 1,6-di(2,4,6-triphenylpyridinium-l)hexane, 1,4-di(N-methyl-4,6-diphenylpyridinium-2)benzene, and 2,7-di(N-methyl-4,6-diphenylpyridinium-2)fluorene in solutions of DMF and MeCN in the potential range from−0.8 to −1.7 V (SCE) was studied by CV. The successive formation of stable radical cations, biradicals, and dianions was investigated by semiempirical MO calculations at the PM3 level.     

Reductive cleavage of dichalcogenide bonds

The kinetics of reductive cleavage of the dichalcogenide bond in dimeric Schiff's bases ArEEAr (E=S, Te) induced by indirect electron transfer byin situ generated bridged bispyridinium radical cations and biradicals was studied by cyclic voltammetry. It was shown that the dependence between the apparent rate constants of intermolecular electron transfer and the electron-withdrawing properties of diaryldichalcogenides is violated. The mechanisms of homogeneous (chemical) and heterogeneous (electrochemical) reductive cleavage of diaryldichalcogenides were discussed. For Part 2, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1522–1526, August, 1999.     

Metal-catalysed cleavage of carbon-carbon bonds

Reactions cleaving carbon-carbon bonds with the assistance of transition metals as the catalyst have provided various molecular transformations that are otherwise difficult to execute, opening a scenic avenue along organic synthesis. Construction of structural motifs like medium-sized carbocycles and chiral quaternary carbon centres have been set within an access of such paradoxical approaches in the past decade.     

On the mechanism of formation of dimeric and reduced products from an α-halo amide with sodium methoxide

Treatment of 2-bromo-N,N-dimethyl-2,2-diphenylacetamide 1 with sodium methoxide in 2,2-dimethoxypropane furnishes mixtures of the reduced product 2 and the dimer 5. Crossing experiments have shown that 2 is not a precursor of 5, supporting thereby the S_RN1 mechanism for the formation of both 5 and 2.     

Structure of the product of reaction of 3-phenyl-3-chloro-2-oxopropionate esters with sodium methoxide

Using x-ray diffraction, mass spectral studies, IR and¹H and¹³C NMR, the unusual product obtained by reaction of 3-phenyl-3-chloro-2-oxopropionate esters with sodium methoxide has been found to be 2,5-diphenyl-3,6-bis(methoxycarbonyl)-2-methoxy-1, 4-diox-5-ene. The conformation of the heterocycle is semi-chair. The methoxy group and the methoxycarbonyl substituent at C⁶ are axially situated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1427–1431, June, 1991.     

Cyclic imides IV. The reaction of some N-substituted nitrophthalimides with sodium methoxide

Treatment of methyl 4-nitrophthalimidoacetate (I) with sodium methoxide in refluxing methanol results in a Gabriel-Colman rearrangement to give 7 - nitro-4-hydroxy-3-carbomethoxy-1(2H) - isoquinolone (II). Under the same conditions, N-substituted 3-nitrophthalimides (IV) yield N-substituted 3-methoxyphthalimides (V).     

Electrodialysis in a non-aqueous medium: production of sodium methoxide

A method is described for the production of an alkali alkoxide from an alcohol and a salt by way of electrodialysis. The principle involves the double decomposition of a salt and an alcohol. In effect, an alcohol is split into protons and alkoxide ions, the latter forming the alkoxide with the metal ions of the salt. This finding opens new venues of application and offers opportunities for new chemical processes.     

The reversible consecutive mechanism for the reaction of trinitroanisole with methoxide ion

Although the competitive mechanism for Meisenheimer complex formation during the reaction of 2,4,6-trinitroanisole with methoxide ion in methanol is generally accepted, no kinetic evidence has been presented to rule out a reversible consecutive mechanism. Simulation of the competitive mechanism revealed that a fractional order in [MeO(-)] is predicted by the latter. Conventional pseudo-first-order analysis of the kinetics resulted in cleanly first-order in [MeO(-)], which rules out the competitive mechanism. The kinetic data are consistent with the reversible consecutive mechanism, which is proposed for this important reaction. An intermediate is required for this mechanism, and we propose that a dianion complex (III) is formed reversibly from the initial 1,3-σ complex (I). The trimethoxy complex (III), the (1)H NMR spectrum of which was observed earlier by Servis (Servis, K. L. J. Am. Chem. Soc. 1965, 87, 5495; 1967, 89, 1508), then eliminates methoxide ion reversibly to form the 1,1-σ complex product (II).     

Titration of thiacetazone and isoniazid with sodium methoxide in non-aqueous medium

Thiacetazone and isoniazid dissolved in dimethylformamide can be accurately titrated with sodium methoxide in benzene-methanol mixture, with o-nitroaniline as indicator. Sodium 4-aminosalicylate does not interfere.     

Reduction of carbon-carbon double bonds and hydrogenolysis by sodium hypophosphite

Sodium hypophosphite plus palladium-charcoal is a mild, economical, selective system for the reduction of carbon-carbon double bonds and hydrogenolysis of benzyl ethers and benzyl carbonates.