Reactions of glycals with xenon fluoride: an improved synthesis of 2-deoxy-2-fluorosaccharides

The 1,2-double bond in acetylated glycals has been fluorinated with XeF₂ in the presence of BF₃ to give 1,2-deoxy-1,2-difluorosaccharides. A mechanism for this reaction has been proposed. This method represents an improvement in the synthesis of 2-deoxy-2-fluorosaccharides.     

Reaction of iron(II) with 1,2-cyclohexanedionedioxime in acid solution

Information about a decomposition of 1,2-cyclohexanedionedioxime in 0.1N acid has been presented. A spectrophotometric study of the reaction of Fe(II) with 1,2-cyclohexanedionedioxime in dilute, acetate buffered solutions containing no ammonia or amine has been reported. The ratio of 1,2-cyclohexanedionedioxime to Fe(II) was found to be 2:1 by JOB's method. The solid compound formed when an excess of 1,2-cyclohexanedionedioxime is added to more concentrated Fe(II) solutions has been studied. Analysis of the vacuum-dried solid is in agreement with the theoretical composition of the compound Fe(DH)₂.2H₂0.     

Isomerization of 1,2-diiodoethylene in a laser-induced chemical reaction of I2 + C2H2

A laser-induced chemical reaction of I₂ + C₂H₂ has been studied and the formation of cis and tians isomers of 1,2-diiodoethylene has been observed. The ratio of the two isomers of 1,2-diodoethylene changes markedly upon changing the laser wavelengths of excitation of the I₂ molecule     

Generalized structural and kinetic relationships for 1,2-shifts of a hydrogen atom in carbocations and neutral compounds

Dynamic PMR has been used in a kinetic study of degenerate rearrangement of 5,6-X₂-1-H-1, 2-dimethylacenaphthylenonium ions (X=CH₃, Br), accomplished by means of a 1,2-shift of the hydrogen atom. It has been found that the free energy of activation of the 1,2-shift of the H atom in the 5,6-X₂-1-H-1,2-dimethylacenaphthylenonium cation (X=H, CH₃, Br), in the 1-H-1,2-dimethylcyclopentyl cation, and in 5-H-1,2, 3,4,5-pentamethyl-1,3-cyclopentadiene exhibits a linear correlation with parameters characterizing the electron density on the atom to which the migrant is shifted.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1352–1358, June, 1991.     

Synthesis of benzo-1,3-ditellurole and its precursors

Poly(o-phenyleneditelluride) 6 has been prepared by the reduction of 1,2-bis(trichlorotelluro)benzene obtained by treatment of 1,2-bis(trimethylsilyl)benzene with TeCl₂. The reduction of 6 with NaBH₄ in ethanol solution affords sodium benzene-1,2-ditellurolate, which, upon treatment with methylene bromide, forms benzo-1,3-ditellurole in 40–47% yield. Benzo-1, 3-ditellurole has also been synthesized in 18–20% yeild by the reaction of 1,2-bis(trimethylslyl)benzene with bis(trichlorotelluro)methane, with subsequent reduction of the product, 1,1,3,3-tetrachlorobenzo-1,3-ditellurole.     

1,2-Dimethyl-1,2-diphenyidisilane-1,2-diol and its K,Na, and FeII derivatives. Molecular structure of the all-trans-isomer, 2,3,5,6-tetra-methyl-2,3,5,6-tetraphenyl-1,4-dioxa-2,3,5,6-tetrasilacyclohexane

Hydrolysis of 1,2-dimethyl-1,2-diphenyl-1,2-dichlorodisilane yields 1,2-dimethyl-1,2diphenyldisilane-1,2-diol, which undergoes dimerization into stereoisomeric 2,3,5,6-tetramethyl-2,3,5,6-tetraphenyl-1,4-dioxa-2,3,5,6-tetrasilacyclohexanes under the action of H₂SO₄. Pure all-trans-isomer has been isolated and characterized by¹H NMR and IR spectroscopy and X-ray analysis. The reaction of sodium disilanediolate with FeBr₂ results in the formation of 1,2-dimethyl-1,2-diphenyl-4-ferra(ii)-3,5-dioxa-1,2-disilacyclopentane.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2550–2556, October, 1996.     

The Formation of Thioacylthioketenes by Flash Vacuum Pyrolysis of 1,2-Dithiole Derivatives

Abstract

The formation of thioacylthioketenes has been observed in Flash Vacuum Pyrolysis of various 1,2-dithiole derivatives. In some cases C₃S₂, 1,2-propadiene-1,3-dithione is formed too.     

A linear rod-packing coordination polymer constructed from a non-linear dicarboxylate and the [Zn4O]6+ cluster

A 1-D coordination polymer, [Zn₄O(1,2-BDC)₃]_n (1,2-BDC?=?1,2-benezendicarboxyate), has been synthesized under solvothermal conditions and structurally characterized by single-crystal X-ray diffraction. The coordination polymer contains [Zn₄O]⁶⁺ clusters with a central μ₄-oxygen tetrahedrally coordinated by four Zn²⁺ ions, which stack into a linear rod connected by 1,2-BDC units.     

A study of the reaction of sulfur with organic compounds

The reactions of sulfur with alip-halogen derivatives of 1,2-diphenylethane, 1,2-diphenylethylene, and tetraphenylethane have been studied. A new method for the production of tetraphenylthiophene (from C₆H₅CHClCHClC₆H₅), benzothieno[3,2-b]benzothiophene (from C₆H₅CHClCCl₂C₆H₅), and of 2-phenylbenzo[b] thiophene (from C₆H₅CHBrCHBrC₆H₅) has been developed. On being treated with sulfur, tetraphenyl-1,2-dichloroethane is converted into tetraphenylethylene. 1,2-Diphenylethylene reacts with sulfur in the presence of hydrogen bromide forming 2-phenylbenzo[b]thiophene and tetraphenylthiophene.For part XVII, see [1].     

THE CHAIN STRUCTURE OF 1,2-POLYBUTADIENES PREPARED WITH MOLYBDENUM CATALYST SYSTEMS

The chain structure of 1,2-polybutadienes prepared with molybdenum catalyst systems has been studied by IR, ~(13)C-NMR and T_g method, and the method to regulate the chain structure investigated. It was found that some polar additives, e. g., allyl halides, are able to regulate not only the content of 1,2-units in the polymer, but also its configuration and sequence distribution. Attempt has been made to estimate the sequence length of stereo-isomers of 1,2-units by statistical theory.     

K x-ray emission spectra from natural silicates

Chemical shifts of Si Kα_1,2 and Al Kα_1,2 lines in seven natural silicates has been measured comparatively to the lines of the pure elements. An attempt is made to correlate these shifts to the surroundings of Si and Al in the minerals.     

Using the 1,2‐dihydro‐1,2‐diphosphinine ring as a template for the synthesis of new bicyclic structures and new trans‐chelating bis‐phosphines

The 1,2‐dihydro‐1,2‐diphosphinine decacarbonylditungsten complex 1 has been used as a synthetic equivalent of the corresponding 1,2‐dianion 2 . These two 1,2‐positions can be linked by a (CH₂)₄ bridge to yield a [4.4.0] bicyclic structure 6 whose identity has been confirmed by X‐ray crystal structure analysis. Alternatively, two ω‐iodohexyl chains can be grafted onto these positions and the resulting diiodo derivative 9 transformed into a long‐chain bis‐phosphine 10 by reaction with lithium diphenylphosphide. This bis‐phosphine gives a chelate complex with PdCl₂ whose trans‐stereochemistry was established by X‐ray crystal structure analysis. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:44–48, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20073     

Synthesis of some L-idose derivatives

The synthesis of 3-0-benzyl- and 3-0-mesyl-1,2-0-isopropylidene-β′-L-iodofuranose has been effected on the basis of the intramolecular nucleophilic exchange of a mesyloxy group at C₅ in derivatives of 1,2-0-isopropylidene-α-D-glucofuranose. It has been found that in a system of vicinal primary and secondary mesyloxy groups a selective replacement of the primary mesyloxy group by an acetyl group is possible. It has been shown in benzyl and mesyl ethers of 5,6-anhydro-1,2-0 -isopropylidene-β-L-idofuranose the opening of the oxide ring under conditions of acid hydrolysis with the retention of the isopropylidene group is possible.     

Spectroscopic studies on the initial stages of thermal degradation of polychloroprene

Thermal degradation of polychloroprene under nitrogen, especially at the initial stages, has been studied by using ¹H-NMR, ¹³C-NMR and FT–IR spectroscopy. A model polymer of low molecular weight (M _n = 6300) was prepared to avoid gelation during degradation. None of isomerized 1,2 unit has been found in the original polymer. Allylic rearrangement of 1,2 unit was the first-stage reaction, which was finished within 30 min at 150°C. The extent of HCl loss was proportional to the decrease of isomerized 1,2 unit. It has been suggested that the next-stage reaction is dehydrochlorination of the isomerized 1,2 unit. The presence of terminal vinyl group and the increased amount of olefinic proton were not found in the degraded polymer. The back-biting mechanism involving a six-membered cyclization process is proposed for the dehydrochlorination. The thermal racemization has been also found to take place in the 3,4 unit.     

Pseudoasymetrie dans la serie du benchrotrene I. Synthese des trois glycols ortho-substitues (OC)3CrC6H4(CHOHCH3)2

The three stereoisomeric glycols (CHOHCH₃)₂C₆H₄Cr(CO)₃ have been prepared via 1,2-diformyl- and 1,2-diacetyl-benchrotrenes. The racemic (pseudosymmetric) form and the two meso (pseudoasymmetric) forms of the glycols have been identified by chemical derivatization and analysis of the spectroscopic data. The photochemical decomplexation of these glycols is a specific route for the preparation of the two corresponding benzenic glycols. The stereoselectivity which has been observed in some reactions is discussed.     

Perchloroimidazo[1,2-a] pyridine. Synthesis and nucleophilic substitutions

Perehloroimidazo[1,2-a]pyridine has been prepared and it has been shown that nucleophilic substitution occurs preferentially at C₅ possibly followed by substition at C₇.     

1,2 Enriched polymerization of isoprene by cobalt complex carrying aminophosphory fused (PN3) ligand

Metal-catalyzed selective isoprene polymerization has been a major entry toward cis-1,4, trans-1,4, and 3,4 isomers of polyisoprene, however, 1,2 selective polymerization of isoprene has not yet been achieved due to the steric problem. In this work, difluoro cobalt complexes carrying aminophosphory (-HN-P(=O) ^tBu₂-) fused pyrazol-pyridine ligand has been prepared and characterized. In combination with Mg^n-Bu₂, the formed catalyst unprecedentedly converts isoprene to polyisoprene with 1,2 enchainment up to 50 mol% in a molecular weight controlled polymerization mode. The resultant polymers are fully characterized by NMR, IR, DSC, and GPC. The 1,2 incorporation of polyisoprene is weakly dependent on feeding of Mg^n-Bu₂ and reaction temperature. The weak affinity between Mg²⁺ and allylic terminal of propagating chain is possible for the unique 1,2 irregular insertion and non-irreversible chain transfer and termination reactions throughout the chain propagation. The ability of current catalyst demonstrates a big advantage for application in the development of 1,2 selective polymerization of isoprene, and a potential for access to a new family of polyisoprene. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2286–2293     

Tetrazinodiheteroarene: ‘Charge-Transfer’-Komplexbildung mit Akzeptorverbindungen

Charge-Transfer Complexes of Tetrazinodiheteroarenes with Acceptor Compounds The formation of charge-transfer complexes and radical-ion pairs of donor compounds 1 – 6 with acceptor compounds 7 – 12 has been investigated by means of VIS/NIR-spectroscopic methods. The equilibrium constants K_CT up to 1100_M-1 for the donor/acceptor couple dipyrido[1,2-b:1,2′-e][1,2,4,5]tetrazine ( 2 )/ethylenetetracarbonitrile ( 11 ) and spectra of the CT complexes have been determined in 1,2-dichloroethane solution at 25°. Results are discussed in relation to known CT-complex properties and to voltammetric redox-potentials E_1/2.     

<Emphasis Type="Italic">N</Emphasis>-alkylation of ethylenediamine with alcohols catalyzed by CuO-NiO/<Emphasis Type="Italic">γ</Emphasis>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

A simple method for N-alkylation of 1,2-diaminoethane with different alcohols in a fixed-bed reactor using cheap CuO-NiO/γ-Al₂O₃ as the catalyst has been developed. The present catalytic system was applicable in the N-alkylation of 1,2-diaminoethane with both primary and secondary alcohols. Mono-N-alkylation of 1,2-diaminoethane with low-carbon alcohols resulted in high yields; the yields of tetra-N-alkylation of 1,2-diaminoethane with low-carbon alcohols declined markedly with the increase of the molecular volume of alcohols.     

C2 molecule: formation from bromoacetylene and reactions with cyclohexene or 2,3-dimethyl-2-butene

The C₂ molecule (1,2-ethynediyl) has been prepared by dehydrohalogenation of 1,2-dibromoethylene with an excess of potassium tert-butoxide in 2,3-dimethyl-2-butene as the solvent and the reagent. The major products of this reaction were 2,3-dimethylbut-3-en-2-ol and dibromoacetylene.