bluuebunny/crossref_metadata_2025 huggingface dataset:
Anomalous Reaction Course in the Amidoalkylation With 4‐Substituted 2‐Methoxy N‐Trifluoroacetyl Piperidines
Authors: Callens R. E. A. , Duquet D. , Borremans F. A. M. , Anteunis M. J. O.
Published: September 2010

Amidoalkylation of suitably substituted benzo[b] furans and benzo[b] thiophenes with 2‐methoxy‐N‐acyl‐piperidines and morpholines gave very low yields of the 2‐(2'‐benzo[b] furanyl)‐, and 2‐(2'‐benzo[b] thienyl) piperidine derivatives. The amidoalkylation of 3‐phenyl‐benzo[b] furan with the isomeric mixture of the 4‐methyl‐2‐methoxy‐N‐trifluoroacetyl piperidines however gave a good conversion but trans‐4‐methyl‐2‐(2'‐(3'‐phenyl) benzo[b] furanyl)‐N‐trifluoroacetyl piperidine is only the minor product formed. Mass spectroscopy, H and 13C NMR spectroscopy proved that the major product is l‐trifluoroacetylamino‐3‐methyl‐5, 5‐bis (2'‐(3'‐phenyl)‐benzo[b] furanyl)‐pentane.
Anodic Methoxylation of Heterocyclic Compounds. Part II. Anodic Methoxylation of 4‐Methyl‐And 4‐T. Butyl‐N‐Trifluoroacetylpiperidine
Authors: Duquet D. , Callens R. E. A. , Borremans F. A. M. , Anteunis M. J. O.
Published: September 2010

Anodic methoxylation of 4‐methyl‐and 4‐t.butyl‐N‐trifluoroacetyl‐piperidine results in a 4:1 mixture of the trans‐and cis‐2‐methoxy derivatives. The isomeric 4‐methyl derivatives can be separated on a preparative scale by gas chromatography, while the 4‐t.butyl derivatives were purified by reversed phase chromatography on a (heptafluorodecyl) dimethylsilyl bonded phase.
2‐Pyrilideniminobenzohydroxamic Acid as Analytical Reagent for the Spectrophotometric Determination of Vanadium(V)
Authors: Salinas F. , Jiménez‐Arrabal M. , Durán I.
Published: September 2010

The synthesis and analytical properties of 2‐pyrilideniminobenzohydroxamic acid (2‐PIBHA) as well as its reactivity with inorganic ions are described.

The reaction between 2‐PIBHA and vanadium(V) was studied and two new methods for the determination of vanadium(V) are proposed: one in methanol‐water medium (40:60%, V:V) and the other one using an extraction in isoamyl alcohol. Fundamental characteristics of the first one are: λ=487 nm, β=3518 1.mol−1.cm−1

application range: 3 to 8 ppm of V(V), Sandell sensitivity (1): 1.4×10−2 μg V(V) cm−2 and for the other one: λ=485 nm, π=5080 1.mol−1.cm−1, application range: 0.6 to 1.6 ppm of V(V) and Sandell sensitivity: 1.02×102 μg V(V) cm−2 (refered to the aqueous phase).

Both methods were applied with sucess to the determination of vanadium(V) in steel.
Application of Linear Free Energy Relationships (LFER) in the Aromatic Hydroxylation of Anisoles by Chromic Acid in Acetic Acid‐Water Mixtures
Authors: Musala Reddy P. , Jagannadham V. , Sethuram B. , Navaneeth Rao T.
Published: September 2010

Kinetics and mechanism of aromatic hydroxylation of anisoles by chromic acid has been investigated in 50° aqueous acetic acid. The reaction followed second order kinetics, first order each in [substrate] and [oxidant] at constant [H+] and ionic strength. The effect of meta and para substituents on the reaction rates has been studied. The application of LFER to the rates reveals that the site of attack is at the ortho carbon atom but not at the oxygen atom.
[2+2] Cycloaddition Reactions of Isothiazoles Intramolecular Nucleophilic Attack On Isothiazolium Salts Preparation of New β‐Lactam Systems Based on Isothiazole Nucleus
Authors: Hassan Mohamed E.
Published: September 2010

[2+2] cycloaddition reactions of isothiazoles with diphenyl ketene afford new fused β‐lactam systems. The intramolecular nucleophilic attack of carbanions on isothiazolium salts is found to take place on the ring sulphur atom. 2‐H‐2‐benzoyl‐1, 3‐thiazines were prepared and allowed to react with diphenyl ketene, or with acid chloride in the presence of a tertiary amine, to afford the corresponding β‐lactams.
Molecular Complexes of Cyclophanes. Part V π‐π Molecular Complexes of Multibridged Cyclophanes With Tetracyanoethylene and 2‐Dicyanomethylene Indane‐1,3‐Dione
Authors: Mourad Aboul‐Fetouh E. , Eltamany El‐Sayed H.
Published: September 2010

The intermolecular charge‐transfer absorption spectra of tris‐, tetra‐ and penta‐bridged cyclophanes as β‐donors with tetracyanoethylene as well as 2‐dicyanomethylene indane‐1,3‐dione as β‐acceptors have been measured in methylene chloride at 22°C. Evidence of the strain and molecular structure of the β‐donors studied is to be seen from the values of λmax of the longest wavelength charge‐transfer (CT) band as well as the equilibrium constant of formation. All molecular complexes with tetracyanoethylene have been isolated and their constitution, melting points and infrared spectra are described. The tetra‐bridged cyclophane has proved to be the strongest β‐base of all β‐donors examined. Stoichiometry, equilibrium constant of formation and molar extinction coefficients of the molecular complexes under investigation have been determined.
Helicenes: Synthèse Photochimique Et Étude Rmn 19F, 13C et 1H De Fluoro‐1‐Hexahelicenes Et Fluoro‐1‐Heptahelicenes
Authors: Gorsane M. , Defay N. , Martin R. H.
Published: September 2010

1‐Fluorohexahelicene, 1‐fluoroheptahelicene and 12 substituted derivatives of these fluorohelicenes have been synthesized by the photocyclodehydrogenation of 1‐fluoro‐11‐styrylbenzo[c]phenanthrenes (Table 2) and 1‐fluoro‐13‐styrylpentahelicenes (Table 4) respectively. The photocyclisations to heptahelicenes were accompanied in five cases, by a side reaction, namely a protodefluoration. A new synthesis of heptahelicene is described (25±18: 40%). 1H, 19F and 13C‐NMR spectra are discussed. 19F and 13C‐NMR spectra of 1‐fluoro‐, 1‐fluoro‐13‐methyl‐ and 1‐fluoro‐13‐methoxycarbonylpentahelicene (8d, 8a and 8 R=‐CO2CH3) are also included.
Concentration Gradients of Some Minor Components In Human Tooth Enamel
Authors: Verbeeck R. M. H. , Driessens F. C. M. , Borggreven J. M. P. M. , Wöltgens J. H. M.
Published: September 2010

Rods with a cross section of 3 mm2 were prepared from the labial surface of premolars extracted either 0.5, 1.5 or 3.5 years after eruption. Enamel slices with a thickness of 100 μm were cut from these rods at a distance of 100 μm apart from each other. The infrared spectra of these slices showed that the carbonate and HPO42− content of enamel increase with depth, whereas the A‐type CO32− and OH− content decrease with depth. A possible involvement of these minor components in posteruptive maturation could not be detected.
Metal‐Solvent Interactions of Iron and Naphthalocyanines With Thionyl Chloride: An Xps Approach
Authors: Riga Joseph , Savy Michel , Verbist Jacques J.
Published: September 2010

X‐ray photoelectron spectroscopic investigations have been performed on phthalocyanine and naphthalocyanine samples previously exposed to thionyl chloride or dissolved into thionyl chloride solutions. With Fe and Mo compounds, fast oxidation of the central metal has been observed, and the data illustrate the dissociative character of the SOCl2 chemisorption.
Synthesis of Succinoylated Inulin and Application as Carrier For Procainamide
Authors: Vermeersch Joan , Schacht Etienne
Published: September 2010

Inulin was succinoylated by reaction with succinic anhydride using 4‐dimethylaminopyridine as acylation catalyst. The corresponding polyacid was activated by treatment with 1,1′‐carbonyldiimidazol and subsequently coupled with the N‐glycyl derivative of procainamide.
Normal Coordinate Analysis of Orthonitrate Anion NO
Authors: Hase Y.
Published: September 2010

Normal coordinate treatment was carried out for the orthonitrate anion NO43− to investigate the vibrational force field and the normal modes of internal vibration. Based on the differences between the observed and calculated fundamental wavenumbers, the internal tension k (NO43−) was found to be almost 0.25 mdyn. Å and for this value of k (NO43−) the Urey‐Bradley force constants adjusted by the least squares calculations were obtained to be K (N‐O)=1.743, H(ONO)=0.574, and F(O…O)=1.261 mdyn/Å
Oxydation D'Alcènes Cycliques Par L'Iodylbenzène Catalysée Par L'Acetylacétonate De Vanadyle
Authors: Barret R. , Pautet F. , Daudon M. , Mathian B.
Published: September 2010

Iodylbenzene with vanadyl acetylacetonate oxidizes cyclic alkenes, the experimental results accord with a free radical oxidation mechanism.
Synthese Und Eigenschaften Geminaler Bisphosphazide Und Bisphosphinimine Kristall‐Und Molekülstruktur Von (δ)‐3‐Amino‐2‐Cyan‐7‐(Diphenylphosphinoyl)‐5,5‐Diphenyl‐4‐Aza‐5λ5‐Phospha‐2,4‐Heptadiensaure‐Methylester
Authors: Saalfrank R. W. , Ackermann E. , Fischer M. , Weiß B. , Carrié R. , Danion D. , Peters K. , Von Schnering H. G.
Published: September 2010

Reaction of methyl 3,3‐diazido‐z‐cyanacrylate (7) with triphenylphosphane leads to a geminal bisphosphazide 11 and bisphosphinimine 12 respectively.

The structure of methyl (E)‐3‐amino‐z‐cyan‐7‐(diphenylphosphinoyl)‐5,5‐diphenyl‐4‐aza‐5λ5‐phoepha‐2,4‐heptadienate (16) was established by X‐ray analysis.
Infrared Spectrum (3000–500 cm−1) OF 2,4,5‐Trichloro‐6‐[(Diethylamino)Methyl] Phenol Oh and Od in the Solid State
Authors: Rospenk M. , Zeegers‐Huyskens TH.
Published: September 2010

The infrared spectra of 2,4,5‐trichloro‐6‐[(diethylamino)methyl]phenol and its deuterated analogue have been studied in the solid state. The bands observed in the vOH(OD) region are ascribed to a Fermi resonance interaction involving the 2OH(OD), 2OH(OD) +yOH(OD) and 2yOH levels.
Étude De La Réactivité De Composés Enaminocarbonyles Vis‐à‐Vis De L'Isocyanate Et De L'Isothiocyanate De Phényle
Authors: Maquestiau A. , Vanden Eynde J.‐J. , Monclus M.
Published: September 2010

Reactions between 4‐amino‐3‐penten‐2‐one, ethyl 3‐amino‐2‐butenoate or 3‐amino‐2‐butenanilide and phenyl isocyanate yield mixtures of N‐ and C‐adducts. Quantitative data allow to check the influence of the electronwithdrawing groups in the enaminocarbonyl precursors and of the solvent polarity on the course of these reactions.

Starting from the same derivatives and phenyl isothiocyanate, only C‐adducts are isolated.

Ethyl 2‐methyl‐3‐amino‐2‐butenoate adds phenyl isocyanate or isothiocyanate on the nitrogen atom of the amino group while ethyl 3‐methylamino‐2‐butenoate adds the same electrophiles on the C(2) atom.
Cristallisation D'Une Variété Triclinique De Yb(PO3)3
Authors: Rzaigui M. , Kbir Ariguib N.
Published: September 2010

A new crystal form of Vb(PO3)3 has been prepared, Its absorption IR and main crystallographic characteristics have been determined. This polyphosphate variety crystallizes with a triclinic cell: a=8.361(3), b=7.508(1), c=6.237(5)Å α=86.02(3)*, β=103.35(6)*, γ=90.92(1)*, V=380 Å3, Z= 2 and a space group Pl or Pl.
Homolytic Substitution in Trialkyltin Iodides by Photochemically Generated Iodine Atoms. III. Mechanism and thermodynamics
Authors: De Ryck P. H. , Verdonck L. , Van Kelen G. P. Der
Published: September 2010

A detailed reaction mechanism for the homolytic substitution of trialkyltin iodides by iodine atoms is presented.

The thermodynamic parameters, ΔH, ΔS and ΔG are calculated for the different reaction steps.
Study of Bis [N, N1‐Dicyclopropyldithiooxamidato (‐1)‐S,S'] Palladium(II) by X Ray Diffraction, UV‐VIS and IR Spectroscopy
Authors: Hofmans H. , Desseyn H. O. , Lenstra A. T. H.
Published: September 2010

Pd C16 H22 N4S4, Mr=505.0, monoclinic, P/c, Z=4, a=14.880(8), b=8.100(5), c=17.876(6) Å, B=110.50(4)Å at 150 K, V=2018(3)Å3, Dx=1.66 Mg m−3, λ(MoK)=0.7107 Å, μ=1.306 mm−1, crystal size 0.1×0.1×0.2 cm., F(000)=1024, Rw=0.10 for 2178 reflections with I>2σ(I) out of 3568 independent measurements.

The structure contains two crystallographically independent Pd atoms situated at inversion centers. Each Pd is surrounded by four S atoms in a square‐planar coordination. The distribution of bond lengths in the organic ligands suggests ionized thiolimid forms with extensive‐electron delocalization over the entire carbon‐nitrogen skeleton.

The UV‐Vis spectrum of the PdL2 (L=C3H5NCSCSNHC3H5) is compared with the spectra of related complexes and the absorption bands are assigned. An IR vibrational analysis is given for the complex in the solid state and in solution.
Méthylation En Phase Gazeuse De Quelques Fonctions Organiques Par L'Ion Diméthyliodonium
Authors: Jortay C. , Flammang R. , Maquestiau A.
Published: September 2010

Electron impact ionization of iodomethane at high pressure (∼ 1 torr) yields high concentrations of dimethyliodonium ions (CH3CH3). Their reactivity towards various functional groups has been studied by mass spectrometry techniques, including in some instances collisional activation. Most of the compounds studied show the methylation process, except aliphatic alcohols and some aromatic compounds like benzene, anisole, furan, thiophene. Nitriles and isonitriles present a very high methyl cation affinity. Other ionization processes have also been observed, e.a. protonation, charge exchange and hydride abstraction. The degree of competition between these processes depends on the nature of the functional groups. Some unusual ion structures have been detected for isonitriles and pyridines.
Synthèses Asymétriques et Synthèses Asymétriques Potentielles D'α‐Amino Alcools: Hydroxyamination D'Oléfines par la Méthode de Sharpless
Authors: Hassine B. Ben , Gorsane M. , Pecher J. , Martin R. H.
Published: September 2010

Optically active α‐amino alcohols have been synthesized by Sharpless method with (‐)‐10,11‐dihydroquinine 2 and (R) ‐ (‐)‐pantolactone 8 as chiral inducers.

Five secondary (dl)alcohols: 3,4,5,6,7 and (dl) 2‐hydroxyheptahelicene 1 have also been used to prepare the intermediate diastereomeric (dl)α‐hydroxy carbamates 9. The highest inductions were obtained with (‐)‐10,11‐dihydroquinine and (E)‐stilbene (e.e. ≥98%) and with (dl)2‐hydroxyheptahelicene and (E)‐stilbene (d.e. ≥98%).
Étude du Polymorphisme et de L'Intersolubilité de Triglycerides Palmito‐Oleiques par Diffraction RX de Poudres et Analyse Calorimétrique Différentielle
Authors: Gibon V. , Durant F.
Published: September 2010

The study of the polymorphism and the intersolubility of some palmitic p and oleic O triglycerides: PPP, OPP and POO, has been performed using differential scanning calorimetry and powder X‐ray diffraction.

Binary and ternary phase diagrams have been constructed by differential scanning calorimetry; the different polymorphic forms have been verified by variable temperature X‐ray powder diffraction. Each system has been studied by two ways: after melting and quenching, and after tempering a few months at room temperature. The construction of those phase diagrams shows the formation of solid solutions, monotectic interactions …, according to the nature and the polymorphic form of the triclycerides.
Mechanism of Ester Aminolysis in Aprotic Media and Specific Solvent Effects
Authors: Nagy Otto B. , Reuliaux Victor , Bertrand Nicole , van Der Mensbrugghe Anne , Leseul Jean , Nagy Janos B.
Published: September 2010

The n‐butylaminolysis of nitro‐substituted 4′‐nitrophenyl benzoates and cinnamates as well as of phenylacetates in aprotic solvents is governed by a kinetic law implying higher order terms in nucleophile. It is shown that the attacking nucleophile forms a n‐π type molecular complex with the substrate before reaching the transition state in the subsequent kinetic step. This molecular complex is a true reaction intermediate as evidenced by the observed negative activation enthalpy. Other nucleophile molecules intervene as general base catalysts. Tertiary amines also catalyse the reaction. Their catalytic activity is linearly related to their hydrogen bond forming ability and it is not a direct function of their proton basicity. By varying the nucleophile structure, an excellent Brönsted relationship could be obtained for the first time in aprotic media, the ß of which confirms that the catalytic collapse of tetrahedral intermediate is the rate determining step. The reaction of cinnamates turns out to be less sensitive to structural changes of the substrate than is the reaction of benzoates as shown by the corresponding Hammet σ values. The electronic effects of 2‐nitro groups are strongly solvent dependent. Once more, it is established that whenever specific solvent effects (π‐donor or n‐donor ability) are present, they dominate the overall effect. A general reaction mechanism is proposed which not only explains the various roles played by the nucleophile but also accounts successfully for the great variety of kinetic schemes observed in aprotic media.
X‐Ray Photoelectron Spectroscopy of Sulfur Containing Ni/SiO2 Catalysts
Authors: Montes M. , Genet M. , Hodnett B. K. , Stone W. E. , Delmon B.
Published: September 2010

Attempts were made to regenerate two Ni/SiO2 catalysts which were exposed to sulfur‐containing compounds. Attempted regeneration was by oxidation followed by reduction. The amount of sulfur present after these treatments was followed by chemical analysis and X‐ray photoelectron spectroscopy. Oxidation and reduction was successful in removing a large part of the sulfur but catalytic activity for benzene hydrogenation could not be restored. The XPS data indicate that the small amounts of sulfur which remained after treatment in hydrogen were located largely in the bulk rather than at the surface of the nickel particles.
Synthesis of a Protected Acetylene Dipeptide Isostere
Authors: van Marsenille M. , Gysen C. , Tourwé D. , van Binst G.
Published: September 2010

A racemic dipeptide analogue of Leu‐Gly in which the peptide bond is replaced by a carbon‐carbon triple bond has been prepared. Key steps are the use of a Mitsunobu reaction to introduce a phtaloyl‐protected aminogroup and subsequent Jones oxidation of a primary alcohol to the carboxylic acid.
Dihydronaphtalène Carbolactone‐1,8: Aromatisation en Présence D'Isocyanate de Phényle
Authors: Bouaziz Z. , Laharotte C. , Rougny A. , Fillion H.
Published: September 2010

The aromatization of conjugated dihydronaphtalene carbolactone‐1,8 with Pd‐C and phenylisocyanate is described; the reaction is accelerated in presence of this hydrogen acceptor.
Étude de la Réaction Entre la 5‐Amino‐2,4‐Dihydro‐4‐|(Phénylamino) Méthylène|‐2‐Phényl‐3H‐Pyrazole‐3‐One et Le 3‐Oxobutanoate D'Éthyle
Authors: Maquestiau A. , Vanden Eynde J.‐J.
Published: September 2010

Reaction between the title compounds, when carried out in refluxing chlorobenzene, leads to a mixture of three products: ethyl 2,3‐dihydro‐3‐oxo‐1H‐pyrazolo |3,4‐b|pyridine‐5‐carboxylate and two isomeric pyrazolo |1,5‐a| pyrimidinediones.

Possible reaction pathways are proposed and dependance of several experimental parameters on the distribution of the final products is discussed.
Homolytic Substitution in Trialkyltin Iodides by Photochemically Generated Iodine Atoms. IV. Evaluation of Solvent Effects on the Electron Donor Acceptor Complexes and the Reactivity of Alkylmetals
Authors: De Ryck P. H. , Hoste S. , van Der Kelen G. P.
Published: September 2010

The spectrophotometric properties of the trialkyltiniodide‐iodine charge transfer complexes in solution are found to depend on the nature of the solvent. The correlations of these solvent shifts of the absorption bands with various solvent properties are discussed within the frame of the Onsager model of dielectrics. Thus data like dipole moments and stabilization energies of excited states can be obtained.

Furthermore a kinetic study of the reactivity of three trialkyltin iodides with iodine atoms has been made in different solvents. The correlation between the absolute rate constants and the polarity (dielectric constant) of the medium suggests increasing solvation of the activated complex with increasing bulkyness of the alkylsubstituent.

The solvent free energy of the initial reactant, the excited CT complex, could be calculated from two independently obtained differences of free energies, i.e. the solvent free energy Esolvent going from the standard solvent to the actual solvents and δΔGsolv,x≠' determined from kinetic experiments at different temperatures.
Synthèse et Étude des Propriétés Spectroscopiques D'Halogénures de Benzène Tellurenyle Orthocarbonyles
Authors: Piette J. L. , Pardon M. C. , Weber R. , Baiwir Et M. , Liabrès G.
Published: September 2010

General preparation and chemical properties of ortho carbonyl benzene tellurenyl halides are reported. The cis conformation of the oxygen of the carbonyl group and the tellurium atom is in all cases detected by NMR and IR spectroscopies.
Cervicol, a Further Secodolastane Diterpene from the Marine Brown Alga Dictyota Cervicornis kützing (Phaeophyceae, Dictyotaceae)
Authors: Teixeira V. L. , Tomassini T. , Kelecom A.
Published: September 2010

Cervicol (6) has been isolated from the marine brown alga, Dictyota cervicornis and is shown by spectral methods to be a new secodolastane diterpene.
On the Synthesis and Conformational Aspects of 2‐methyl and 2‐t. Butyl Substituted 1,3‐Cyclopentane and Cyclohexane Diols
Authors: D'Haenens L. , van de Sande C. C. , Tavernier D. , Vandewalle M.
Published: September 2010

The diastereomers of 2‐methyl‐1,3‐cyclopentanediol, 2‐t.butyl‐1,3‐cyclopentanediol, 2‐methyl‐1,3‐cyclohexanediol and 2‐t.butyl‐1,3‐cyclohexanediol have been prepared. Configurational assignment and some conformational aspects are described.
Bioactive Polymers XVI. Immobilization of Novocaine on BiozanR
Authors: Dumitriu S. , Popa M. I. , Simionescu C. R.
Published: September 2010

Novocaine was immobilized on BIOZANR after activation with dicyclohexylcarbodiimide.

Under the optimum coupling conditions described (temperature, reagent concentration) a reaction product with novocaine content of 37% was obtained. Penicillin G was then bound to the BIOZAN‐novocaine complex resulting in an antibiotic with prolonged action and high water solubility.

Penicillin G is continuously released after hydrolysis in acid and basic media.
Preparation of White Marble Samples for Instrumental Neutron Activation Analysis
Authors: Moens L. , De Rudder J. , De Paepe P. , Waelkens M.
Published: September 2010

When sampling white marble for INAA, using a diamond core drill and circular saw the inevitable contamination can be removed by etching the samples with HNO3 (1N). Samples are etched for five minutes, first immediately after extraction and a second time after irradiation. For cooling the drill and saw, distilled water must be used whereas pro analysi acid is shown to be sufficiently pure to prepare the etchant with.
Solubility Behaviour of Mg‐Containing β‐Ca3 (PO4)2
Authors: Verbeeck R. M. H. , De Bruyne P. A. M. , Driessens F. C. M. , Terpstra R. A. , Verbeek F.
Published: September 2010

The solubilities of synthetic β‐Ca3 (PO4)2 [TCP] and Mg‐containing β‐Ca3 (PO4)2 [TCMP] were determined in the system Ca(OH)2‐Mg(OH)2‐H3PO4‐KCl‐H2O at 25° C. The thermodynamic solubility product of TCP is found to be (1,14 ± 0.10) x 10−30 mol5. l−5. The incorporation of Mg2+ results in a remarkable stabilization of the β‐TCP structure as reflected by a drastic decrease in the amount of solid dissolved for TCMP compared to that for TCP and by the fact that the solutions are undersaturated with respect to calciumhydroxyapatite. On the basis of solid state chemical and thermodynamical principles the solubility behaviour of TCMP solid solutions is discussed. Indications are found that magnesium whitlockite possibly precipitates during the equilibrations of TCMP.
Déplacements Homolytiques Intramoléculaires 10‐Additions Radicalaires À des Peresters γ‐Insatures Influence de Divers Facteurs Sur la Formation D'Esters Cycliques
Authors: Kharrat A. , Gardrat C. , Maillard B.
Published: September 2010

Free radical additions of ZH compounds to γ‐unsaturated peresters have been performed in order to determine the limitations upon the induced decomposition (steric effects, type of unsaturation, nature of the neighbouring atom of the perester function). Using γ‐ethylenic peresters and percarbonates led generally to lactones and cyclic carbonates.
Photocyclisation of Diphenylamine as a Fluorogenic Reaction for Photochemical‐Fluorimetric Analysis
Authors: Fall C. A. T. , Diop A. , Aaron J. J.
Published: September 2010

The photocyclisation reaction of diphenylamine has been studied spectrophotometrically and spectrophotofluorometrically in several organic solvents at room temperature. A two‐step photoreaction takes place, with the formation of carbazole as the main fluorescent photoproduct. In most solvents, the fluorescence intensity of diphenylamine is increased upon UV irradiation, reaching a maximum within 10 to 15 min. Photochemical‐fluorescence enhancement factors range between 3 and 35. Linear log‐log calibration plots are obtained over several orders of magnitude in concentration units. Photochemical‐fluorimetric limits of detection are as low as 20 μg 1−1. The photocyclisation of diphenylamine is shown to be a very useful fluorogenic reaction for its quantitative analysis.
Chemistry of Methyl 1‐Butyl‐Cyclopropene‐3‐Carboxylate: The Role of Transition Metal in Reaction Control: Rhodium‐Catalysed Synthesis of a Bicyclobutane, Coppercatalysed Dimerisation, Selective (Tl+++) Oxidation
Authors: Condé‐Petiniot N. , Hubert A. J. , Noels A. F. , Warin R. , Teyssié Ph.
Published: September 2010

Some typical reactions of a cyclopropenecarboxylate(I) were tentatively controlled by the use of transition metal catalysts. The reaction of (I) with methyl diazoacetate (DAM) afforded a dihydropyrazine(III) which was further dehydrogenated photochemically to the pyrazine(IV) whereas, the bicyclobutane(II) was obtained in the presence of rhodium acetate as catalyst. Copper triflate catalysed the ring opening of the cyclopropene ring and a dimer (the octatrienedicarboxylate(V) was thus isolated. Attempts to epoxidize(I) with a peracid (MCPBA) or V0(acac)2 and Mo0(acac)2‐t‐butyl hydroperoxide failed. Up to now, only thallium(III) nitrate afforded satisfactory selective oxidation of (I) (formation of the lactone VII).
Solution Densities of Aqueous Al2(SO4)3 From 50 to 70°C
Authors: Kumar Anil
Published: September 2010

Accurate densities data of aqueous aluminium sulphate solutions at 50, 60 and 70°C are reported with a precision of 30 × 10−6 g cm−3.
Novel Macrocyclic Trichothecenes from Myrothecium Roridum
Authors: Jarvis Bruce B. , Taha Çömezoglu F. , Lee Yin‐Won , Flippen‐Anderson Judith L. , Gilardi Richard D. , George Clifford F.
Published: September 2010

An isolate of Myrothecium roridum (ATCC 60379) produced a series of novel enol ether containing macrocyclic trichothecenes, myrotoxins A‐D, when grown on rice substrate. The stability of the myrotoxins depends strongly on the stereochemistry of the hydroxy group at C12'. In liquid culture, this fungus produced, in addition to myrotoxins A and B, three new macrocyclic trichothecenes, mytoxins A‐C which are related in structure to satratoxins. The myrotoxins and mytoxins are acutely cytotoxic and in vivo toxic agents.
Synthesis and Absolute Configuration of Zonarol. A Fungitoxic Hydroquinone from the Brown Seaweed Dictyoptfris Zonarioides(1)
Authors: Mori Kenji , Komatsu Makoto
Published: September 2010

A total synthesis of both the enantiomers of zonarol 1 was accomplished. Measurements of the ORD‐CD spectra of two bicyclic intermediates coupled with direct comparison of the natural and synthetic zonarol 1 established the absolute configuration of the naturally occurring (+)‐zonarol 1 as 1R, 4aR, 8aR.
Diterpenes from a Soft Coral, Minabea SP., from Truk Lagoon
Authors: Ksebati M. B. , Schmitz F. J.
Published: September 2010

Ten new diterpenoids, minabeins‐1 to −10, possessing the known briarein skeleton have been isolated from a soft coral, Minabea sp., collected from Truk Lagoon, Eastern Caroline Islands. This is the first report of the occurrence of this class of compounds in soft corals. An analysis of the distribution of cembranoids and various cyclized cembranoids among three orders of octorcorals (soft corals, gorgonians, and sea pens) is presented. Structures and relative stereochemistry of the minabeins was determined by extensive1H and13C NMR spectral analysis.
The Chemistry of Lissoclinum Patella
Authors: Sesin David F. , Gaskell Simon J. , Ireland Chris M.
Published: September 2010

Lissoclinum patella is the source of a family of cyclic peptides characterized by the presence of thiazole amino acids. Detailed analysis of 2D COSY 45 NMR data for the Lissoclinum peptides revealed homoallylic coupling between the α‐amino protons both through the peptide bonds and the oxazoline rings. This data was used to reassign the structures of the patellamides A‐C, and to assign structures to three new metabolites prelissoclinamide‐2, prepatellamide‐B‐formate and preulicyclamide.
Reactive Double Bond Systems Via (3+2) Cycloreversion of Heterocycles
Authors: Schaumann Ernst
Published: September 2010

After deprotonation, saturated five‐membered heterocyclic rings give a facile (3+2) cycloreversion. This approach is employed in syntheses of ketenes, thioaldehydes, thioketones, thioketenes and a thioquinone at low temperature. These highly reactive double‐bond systems are usually trapped in situ using (2+2), (2+3), or (2+4) cycloadditions to give various types of heterocycles.
Performances des Faujasites Échangées Avec des Éléments de la Série des Terres Rares Dans Le Processus de Disproportionnement du Toluene
Authors: Azzouz Abdelkrim , Fourar Mokrane , Berrak Abderrezak
Published: September 2010

The process of toluene disproportionation was carried out using modified Y‐type faujasites. The X‐ray diffraction analysis shows that the cation exchange of the NaY zeolite with La(3+) or Ce(3+) causes 311 plane displacement and affects the crystallinity. This effect was not observed when the faujasites were previously exchanged with NH4(+) cations.

The faujasites which have undergone about 73% cation exchange and a programmed calcination gave the best performances. In the temperature range 350–500°C, the toluene conversion was about 20–60 mol. The NaLaY catalysts are slightly more active than those containing cerium, but the latter present a higher selectivity with respect to the main process. Nevertheless, with both types of catalysts the temperature decrease enhances p‐xylene formation.
Effect of Amines on the Kinetics of alkaline Decomposition of Benzyltriphenylphosphonium Chloride in Binary Solvent Mixtures
Authors: Hanna Morcos T. , Khalil Fayez Y. , Beder S. M.
Published: September 2010

The kinetics of decomposition of benzyltriphenylphosphonium chloride by sodium hydroxide was studied in binary aqueous solvent mixtures ranging from pure water to about 70% (v/v) of dipolar aprotic solvents such as DMSO or acetone in presence of a series of aliphatic and aromatic amines. The rate, which is directly proportional to the organic solvent content, was found to increase to a maximum at 0.1 M amine concentration and then to decrease. The small increase in rate due to the addition of amine is explained on the basis of an amine‐water interaction, where the concentration of OH−ions in the solution increases slightly due to the ability of the amines to abstract protons from water molecules in the medium. However, the decrease in rate beyond 0.1 M amine concentration is explained as due to the decrease of hydroxide ion concentration by formation of a weakly ionised quaternary ammonium hydroxide. The observed activation energies, thermodynamic parameters and radii of the activated complex for all solvent compositions are computed. The effect of the bulk dielectric constant on the reaction rate was investigated in the light of the available electrostatic theories.
The Cycloaddition Reaction Between Styrene and 2,3,4,5‐Tetrahydropyridine 1‐Oxide
Authors: Hootelé C. , Ibebeke‐Bomangwa W. , Driessens F. , Sabil S.
Published: September 2010

The cycloaddition of styrene to 2,3,4,5‐tetrahydropyridine 1‐oxide leads, with a high yield, to a 97:3 mixture of the diastereoisomeric isoxazolidines 3c and 4c respectively.
Synthesis and Potential Anticancer Activity for Diaminoalkyl Complexes of Tin Halides
Authors: Eng G. , Engle T. W.
Published: September 2010

A series of dimethyltin dihalide bidentate complexes modelled after analogs of cis‐diammine dichloroplatinum, a widely used anticancer drug, were prepared and tested for anticancer activity. An analogous series of pentacoordinated trialkyltin halides were also prepared and tested for comparison. These compounds displayed toxicity too high to make these complexes useful as anticancer agents.
Functionalization of Isophorone Involving Polychlorination. Part I: Heptachlorination Catalyzed by Dimethylformamide Hydrochloride and Solvolysis Induced by Concentrated Sulfuric Acid
Authors: De Buyck L. , Speybrouck J. , Sulmon P. , De Kimpe N. , Verhé R. , Schamp N.
Published: September 2010

Polychlorination of isophorone (1), catalyzed by dimethylformamide hydrochloride, under drastic conditions afforded mainly 2,2,4,6,6‐pentachloro‐3‐dichloromethyl‐5,5‐dimethyl‐3‐cyclohexenone (3) (35‐45% isolated). Moderate conditions (below 90°C, excess DMF) permitted the isolation of 2,6,6‐trichloro‐3‐dichloromethyl‐5,5‐dimethyl‐2‐cyclohexenone (2) in 45‐55% yield. Selective solvolysis induced by concentrated sulfuric acid was used in the purification of 2 and for synthesis of 6,6‐dichloro‐3‐formyl‐5,5‐dimethyl‐1,2,4‐cyclohexanetrione (4) (45‐58% yield from 3). Side products containing a 3‐trichloromethyl group were converted into carboxylic acids.
The Reactivity of Selenium Dioxide Towards Aromatic Aldehydes Hydrazones, Azines and Phenylhydrazones: Carbonyl Regeneration and a New One‐Pot Oxidation of Aldehydes to Aromatic Acids
Authors: Dekova B. Y. , Evers M. J. , Christiaens L. R. , Guillaume M. R.
Published: September 2010

Selenium dioxide is a mild oxidizing reagent able, in hot D. M. F. solution, to regenerate arylaldehydes from their hydrazones and azines. The same experimental conditions in the case of phenylhydrazones of aromatic aldehydes yield the corresponding substituted benzoic acids. In this respect the behaviour of SeO2 differs from that of benzeneseleninic anhydride.
Synthesis and Thermal Decomposition of 4‐Azidoisoxazoles
Authors: L'abbé Gerrit , Godts Prançoise
Published: September 2010

The diazonium salts derived from 1a, b decompose at 0°C to give α‐cyanodiazoketones 3a, b and, in the case of 1b, also the N‐hydroxytriazole 4. The azides 2a, b were prepared from the diazonium salts at ‐15°C. The diazonium salt from 1c is more stable and can be converted into the azide 2c at 0°C, along with formation of 5 as a side product. Kinetic measurements have been carried out for the thermal fragmentation of 2a, c which indicated that the reactions occur by a concerted mechanism.
Relationship Between the pH‐Dependence of the Half‐Wave Potential and the Limiting Current in Second Reduction Waves of CE Mechanisms
Authors: Muñoz E. , Camacho L. , Avila J. L. , Heras A. M. , Ruiz J. J.
Published: September 2010

Electrode processes involving chemical stages prior to and subsequent to the electric transfer allow the theoretical and experimental separation of the influence of both reactions on the half‐wave potential. This paper contributes a new example to the study of processes corresponding to second reduction wave coupled to CE mechanisms.
Oxydation d'Amines Aromatiques Primaires en Présence du Radical Tritertiobutyl‐2,4,6 Phénoxyle
Authors: Hedoyatullah Mir , Thevenet Francis
Published: September 2010

The trapping of onilino radicals generated by a mild dehydrogenetion of primary aromatic amines, at 20°C, in homogeneous medium or in two‐phase system, by 2,4,6‐tritertiobutylphenoxy radical is carried out and the structures of the corresponding C‐N or C‐C coupling products are established by spectral data (IR, UV, RMN 1H).
Potentiometric Investigation of the Dissociation of α‐Hydroxyisobutyric Acid in Aqueous Sodiumperchlorate Solutions of Unit Ionic Strength at 25°C
Authors: Vantomme Paul , Bouserie Frank L. G. , Thun Harry P.
Published: September 2010

From emf measurements in titrations at constant ligand concentration (cL) the formation function nH is calculated for aqueous solutions of α‐hydroxyisobutyric acid of I=1 at 25°C. From cL = 0.2 M on these functions grow separate, keeping only one cross‐over point in common. Considering then the presence of associated forms a reasonably good agreement was obtained with the experiment. However, after correction of the emf data for all effects leading to a changed activity coefficient of the measuring electrolyte and for the consequent changes in the formal dissociation constant, the data again can best be described by a normal monoprotic dissociation behaviour.
Crystal Structure and Conformation of Short Linear Peptides: Part IV: Glycyl‐Glycyl‐L‐Isoleucine Monohydrate Methanol Solvate
Authors: Wu S. , Tinant B. , Declercq J. P. , van Meerssche M.
Published: September 2010

C10H19N3O4. 1/2CH3OH. H2O, Mr = 279.31, orthorhombic, P212121, a = 35.826 (15), b = 9.793(3), c = 8.969(2)Å, V = 3146(2)Å3, Z = 8, Dx = 1.18 gcm−3, Cukα, λ = 1.5418 Å, μ = 8.10 cm−1, F(000) = 1208, T = 291K, R = 0.072 for 3508 observed reflections. The two molecules have rather different conformation in the main chain. The side chains take a sterically unfavorable conformation characterized by (X11, X12, X2) of (60°, ‐67°, 170°) for molecule A and of (67°, ‐61°, 162°) for molecule B with the ethyl group gauche to both the carbonyl group and the N atom. Three of four 0 atoms of the carboxylate groups accept two H‐bonds. The crystallization conditions ‐ pH and temperature ‐ seem to affect strongly the conformation of peptide in this case.
Application of Cinnamyloxycarbonyl (Coc) Protection During the Synthesis of Coc‐Pro‐MePhe‐MeAla‐OMe. Chain Rupture of the Tripeptide on Chromatography
Authors: Sharma N. K. , Anteunis M. J. O.
Published: September 2010

The preparation of 1‐(cinnamyloxycarbonyloxy)benztriazole (Coc‐OBt), as reported in literature, results in a mixture of 50% Coc‐OBt (6) next to 13%. of 1‐(cinnamyloxy)benztriazole (7). The reagent 6 is stable for several months in the fridge. Coc‐protection of Pro can be obtained in an improved yield by a slightly modified procedure.

Coc‐Pro‐MePhe‐MeAla‐OMe was prepared in good yields using BOP‐Cl as the activator for coupling. In an attempt to isolate the tripeptide by chromatography on SiO2 we found it to decompose into Coc‐Pro and the cyclic dipeptide (DKP) c(MePhe‐MeAla). The same DKP is formed from the dipeptide ester salt Tfa. MePhe‐MeAla‐OMe on standing in COCl3. These findings stress the ease of chain rupture of peptides caused by acidic agents when they possess a triad of N‐alkylated amino acids (3).
Synthesis and Reactions of 3‐Phenyl‐3,4‐Dihydro‐1, 4‐Quinoxalin‐2 (1H) ‐One and its Heterocyclic Analogues
Authors: Olagbemiro T. O. , Nyakutse C. A. , Lajide L. , Agho M. O. , Chukwu C. E.
Published: September 2010

The lactams quinoxalinone 3a, benzothiazinone 3b and benzothiazinone 3c were synthesized by reactions of methyl 2‐bromo‐2‐phenylethanoate 1 with orthosubstituted arylamines 2a ‐ 2c. Subsequent reductive alkylation of the lactams with sodium hydride and iodomethane afforded only the N‐alkylated quinoxalinone 4a and benzothiazinone 4b. Lithium aluminium hydride reduction of the lactams 3a‐3c gave the dihydro‐derivatives 5a, 5b and 5c while similar reduction of the N‐alkylated lactams 4a and 4b yielded the unsaturated quinoxaline 6a and benzothiazine 6b respectively. Lead tetraacetate oxidation of the quinoxalinone 3a furnished the unsaturated quinoxalinone 9 which was N‐alkylated using sodium borohydride in formic acid to give 10. Treatment of the lactams 3a, 3b and 3c with phosphorus pentasulphide produced only the quinoxalinethiol 11 and benzothiazinethione 12. Compounds 11 and 12 were alkylated with iodomethane and sodium ethoxide to give the S‐alkylated products 13 and 14 respectively.
ESR Studies of Some Copper (II) Complexes
Authors: Bhoopathy T. J. , Payami Feridoun , Mohan S.
Published: September 2010

The ESR and optical absorption spectra of four transition metal complexes, copper (II) dichloroacetate, copper (II) trichloroacetate, copper (II) cyanoacetate, and copper (II) N‐acetyl methioninate were recorded at room temperature in powder and solution, and at liquid nitrogen temperature (LNT) in frozen solution with DMF or DMSO as solvent. The g‐parmeters and hyperfine constants were obtained from the spectra. Using optical and ESR data, the covalency factor has also been calculated.
Trans 8‐Tert‐Butyl‐2‐Oxaspiro [4. 5] Decan‐3‐One C13H22O2
Authors: Tinant B. , Declercq J. P. , van Meerssche M. , Picard Ph. , Moulines J. , Lecoustre M.
Published: September 2010

Mr = 210.32, monoclinic, P21/a, a = 41.943(7), b = 6.410(2), c = 10.161 (3) Å, β= 114.42 (2)°, V = 2487.4(11) Å3, Z = 8, Dx = 1.12 gcm−3, MoKα, λ = 0.71069 Å, μ = 0.79 cm−1, F (000) = 928, T = 291K, R = 0.058 for 2248 observed reflections. The trans configuration is observed. The two independent molecules of the asymmetric unit have a similar geometry with perfect chair and envelope conformations for respectively the 6‐ and 5‐membered rings.
Preparation of (S)‐2‐Methylbutylamine and Synthesis of Chiral Isoleucine and Alloisoleucine
Authors: Anteunis M. J. O. , Callens R. , De Nitte M. , Reyniers M.‐F. , Spiessens L.
Published: September 2010

A four‐step synthesis (45% total yield) of a mixture of chiral pure L‐isoleucine and D‐alloisoleucine is reported, via a route comprising anodic oxidation of suitable acylamide precursors. Efficient preparations for (s)‐2‐ methylbutylamine from the cheap parent (s)‐alcohol are described.
Synthesis and Crystal Structure of Bis [1,2,3] Triazolo [1,5‐a:4′,5′‐d] Pyrimidin‐9‐Ones
Authors: L'abbé Gerrit , Godts Françoise , Toppet Suzanne , Meervelt Luc Van , King Geoffrey S. D.
Published: September 2010

The reactions of 5‐azido‐4‐alkoxycarbonyl‐1,2,3‐triazoles with active methylene nitriles (phenylacetonitrile, malononitrile) yield bis‐[1,2,3] triazolo [1,5‐a:4′,5′‐d] pyrimidinones 7 instead of the previously reported3 bis[1,2,3] triazolo[1,5‐a:4′,5′‐e] pyrimidinones 6. The structures were established by 1H and 13C NMR analyses and confirmed by a crystal structure determination of a selected derivative obtained by methylation.
Effet des Substitutants Aromatiques en RMN du Carbone‐13: Extension du Modèle de Smith et Proulx aux Composés Hétérocycliques et Analyse Statistique des Résultats
Authors: Faure Robert , Llinares Jeanine , Elguero Jose , Goya Pilar
Published: September 2010

Three new Q* parameters have been calculated for dimethylamino, amino and tert‐butyl substituents, thus completing a set of fifteen substituents for which F, R and Q* are well characterized. The substituent carbon‐13 chemical shifts of several aromatic heterocycles have been analyzed using the model Δδ=aF+bR+cQ*+d. The set of fifteen substituents (three variables, natural or coded) has been submitted to two statistical treatments. In the first one, with the Fedorov type exchange algorithms it has been possible to select the most significant substituents. In the second one, the possibility to reduce the number of variables has been considered and rejected.
Crystal Structure of 2 ‐(2‐ Amino ‐ 4 ‐ Thiazolyl ‐ 5 ‐ Chloro ) ‐ 2 ‐Z‐Methoxyimino N‐ Methyl Acetamide, C7O2N4 S Cl H9
Authors: Laurent Guy , Norberg Bernadene , Durant Francois
Published: September 2010

Mr = 248.70, dx = 1.53 Mgm−3, C2/c, Z = 8, a = 15.704(1), b = 7.623(1), c = 18.659(4) Å, β = 104.83(1)°, V = 2159.3 Å3, λ CuKα = 1.54178 Å, μ = 46.91 cm−1, F(000) = 1024, T = 293 K, final R value = 0.043, 2190 independent reflections, 1971 considered as observed (I ≥ 2.5 σ (I)) collected on a Enraf‐ Nonius CAD‐4 diffractometer.

The chlorine substitution on the aminothiazol nucleus does not induce any conformational change by comparison with the unsubstituted analogue. This could explain the identical biochemical activity of cefotaxime, a third generation cephalosporin, and its chloro analogue.
Chemoselective Intramolecular Nitrone‐Olefin Cycloaddition : An Efficient Route to Functionalized Cis Hydrindane Systems
Authors: Stanssens Dirk , Keukeleire Denis De , Vandewalle Maurits
Published: September 2010

Isoxazolidines 5a‐c and 8 were obtained via chemoselective nitrone‐olefin cycloaddition in suitably modified 1,4‐cyclohexadienes 1a‐c: 5a and 5c were transformed to highly functionalized cis‐hydrindanes.
Transformation of Quinolines and Anilines Over NiMo‐Al2O3 Catalysts
Authors: Perot G. , Brunet S. , Canaff C. , Toulhoat H.
Published: September 2010

The decomposition of nitrogen‐containing compounds : 1,2,3,4 tetrahydroquinoline, 6‐methylquinoline, decahydroquinoline, orthopropylaniline and 2,6‐diethyl, l‐aniline, was studied at 623 K, 7 MPa in a continuous flow microreactor over two commercial nickel‐molybdenum‐alumina catalysts, (HR346 and HR348, Procatalyse). Decahydroquinoline was found to react very rapidly under the conditions of 1,2,3,4‐tetrahydroquinoline hydrodenitrogenation. The simultaneous transformations of quinoline and anilines showed that the aniline transformation was inhibited by the quinolines. However the inhibiting effect was much less significant with HR348 which also happens to be more active in aniline transformation.
An Exafs Study on Carbon‐Supported Mo and Co‐Mo Sulfide Hydrodesulfurization Catalysts
Authors: Bouwens S. M. A. M. , Koningsberger D. C. , De Beer V. H. J. , Prins R.
Published: September 2010

The structure and dispersion of the active phase present in sulfided Mo/C and Co‐Mo/C catalysts are studied by means of Mo K‐edge EXAFS. EXAFS measurements were carried out at liquid N2 temperature on freshly sulfided catalysts in situ. Due to a high signal‐to‐noise ratio of the experimental data, detailed information about the structural parameters of the active phase can be obtained. The Mo/C and Co‐Mo/C catalysts consist of very small MoS2‐like particles, which contain on average 5 to 6 Mo ions (Mo/C), and 7 to 8 Mo ions (Co‐Mo/C). There are indications for the presence of a Mo‐C interaction in Mo/C and Co‐Mo/C. The Mo‐C coordination distance is estimated to be 1.9 ± 0.1 Å. There are also indications for the presence of a Mo‐Co interaction. The Mo‐Co coordination distance was estimated to be 2.8 ± 0.1 Å.
Crystal structure of 3‐methyl‐4‐pyrimidonium picrate
Authors: Kasende Okuma , King Geoffrey S. D. , Zeegers‐Huyskens Thérèse
Published: September 2010

Crystal structure analysis of the 1:1 complex of 3‐methyl‐4‐pyrimidone with picric acid has shown that the proton from the picric acid is attached to the pyrimidone N(1) to form an O−.....H+‐N bond rather than to the carbonyl group. The complex crystallizes in the space group C2/c with a = 22.357 (5), b = 9.022 (3), c = 13.882 (4) A, B = 98.85 (2) and Z = 8.
Functionalization of isophorone involving polychlorination part IV: Synthesis of 2, 5‐cyclohexadienones related to filicinic acid
Authors: De Buyck L. , De Pooter H. , Schamp N.
Published: September 2010

Cyclohexadienone 2 was obtained in 90% yield from heptachloroisophorone 1 by selective dechlorination and hydrolysis in 90% methanol containing iodide and bisulfite. Reaction of 2 with methanolic sodium methoxide allowed isolation of aldehyde 4 (95% yield) or the intermediate acetal 3 in 65‐75% yield. Substitution of all chlorine atoms with methoxide occurred after conversion of 2 into the methyl enol ether 5, resulting in acetal 8 (55% yield) or aldehyde 9 (55%). Using potassium carbonate in boiling methanol one chlorine atom in 5 was left, resulting in acetal 6 (62%) or aldehyde 7 (95%). Careful hydrolysis of the acetals left the enol ethers intact and yielded the aldehydes 10, 11 and 12 which all show remarkably large geminal coupling constants (2J 13C‐CH=O=22 to 23 Hz). Analogous substitution reactions were performed on the chloromethyl analog 18. The resulting methyl enol ethers with methoxymethyl side chain were exceptionnally resistant to acidic hydrolysis.
Preparative separation of factors B (virginiamycins S) from commercial feed additive formulations
Authors: Sharma N. K. , Anteunis M. J. O.
Published: September 2010

Mixtures of VS1 and VS4 (1) can be preparatively separated by adsorption chromatography on SiO2 with benzene: isobutanol: acetic acid (90: 30: 5) as the eluent system. The purity of the separated congeners was checked by HPLC and H NMR. Although analytically highly efficient eluent systems have been found for similar separations by reverse phase HPLC, this method suffers from difficulties that are big enough as to render this approach less practical for preparative purposes.