bluuebunny/crossref_metadata_2025 huggingface dataset:
Carbon-13 magnetic resonance: hydrogen involvement in γ-anti substituent effects
Authors: Forrest T. P. , Thiel J.
Published: May 2006

Chemical shifts have been determined for the carbons in a series of 3,3-dimethylcyclohexyl derivatives, (substituent = H, CH3, NH2, OH, Cl, Br, I). Comparison of the γ-anti substituent effects at carbons 3 and 5 indicates that presence of axial protons on these carbons causes increased shielding by all of the above substituents. The shielding by γ-anti substituents is decreased by the replacement of either the α or γ protons by methyl groups; the extent of the decrease is dependent upon the substituent and upon the position of the hydrogen which is replaced.
13C lithiation shifts in aldimines and ketimines. Evidence on the configuration of lithiated N-tert-butylimines
Authors: Fraser Robert R. , Chuaqui-Offermanns Noemi
Published: May 2006

The 13C shieldings for a series of aldimines and ketimines have been measured along with the shifts for their 1-lithio derivatives. For those aldimines with a primary or secondary alkyl group attached to nitrogen, the "lithiation shifts" for the attached carbon (C-4) were all upfield due to the change from anti to syn configuration on lithiation. In the ketimines and in the N-tert-butyl aldimines and ketimines, the lithiation shifts for the C-4 carbon failed to provide stereochemical information. The shifts at C-1 and C-2 proved similar to those previously observed for lithiated alkenes.
The kinetics of proton and deuteron transfer from 4-nitrophenylnitromethane and l-(4-nitrophenyl)-l-nitroethane to 2,7-dimethoxy-l,8-bis(dimethylamino)naphthalene in acetonitrile solvent
Authors: Leffek Kenneth T. , Pruszynski Przemyslaw
Published: May 2006

4-Nitrophenylnitromethane reacts with 2,7-dimethoxy-1,8-bis(dimethylamino)naphthalene in acetonitrile in a bimolecular proton transfer, which shows a primary deuterium isotope effect, kH/kD = 12.2 at 25 °C. The large isotope effect on the enthalpy of activation, (ΔHD≠ – ΔHH≠) = 4.6 ± 0.3 kcal mol−1 is consistent with a significant contribution of proton tunnelling to the reaction rate of the protium substrate.The analogous reaction of 1-(4-nitrophenyl)-1-nitroethane with the same base in acetonitrile gives contrasting kinetics and reaction parameters. The reaction is first order, showing no dependence on base concentration. While the isotope effect kH/kD = 9.3 at 25 °C, the enthalpy of activation difference (ΔHD≠ – ΔHH≠) is only 0.5 ± 0.1 kcal mol−1. It is concluded that the 1-(4-nitrophenyl)-1-nitroethane undergoes a slow dissociation, with a very small dissociation constant, followed by a fast association with the base to yield the carbanion ion-pair.
Products of reaction between styrene and some radicals with 2,2-diphenyl-1-picrylhydrazyl
Authors: Kopecky Karl R. , Hall Michael C.
Published: May 2006

Addition of 2,2-diphenyl-1-picrylhydrazyl DPPH to styrene at 75 °C results in little change in the amounts of cis- and trans-1,2-diphenylcyclobutane and 1,2,3,4-tetrahydro-1-phenylnaphthalene, in a slightly smaller amount of 1-phenylnaphthalene, and in a considerable increase in the amount of 1,2-dihydro-1-phenylnaphthalene that are formed. Formation of the styrene trimer 1,2,3,4-tetrahydro-1-phenyl-4-(1-phenylethyl)naphthalene is eliminated completely. Products derived from DPPH are l-(4-nitro-phenyl)-1-phenyl-2-picrylhydrazine 9 and 1-[2,6-dinitro-4-(1,2,3,4-tetrahydro-4-phenyl-1-naphthyl)phenyl]-2,2-diphenylhydrazine, 10. DPPH intercepts the thermally formed Diels–Alder dimer of styrene as soon as it is formed to give the 1,2,3,4-tetrahydro-4-phenyl-1-naphthyl radical.Thermolysis of bis(1,2,3,4-tetrahydro-4-phenyl-1-naphthyl)diazene in the presence of DPPH yields 20% of 10, 10,% of l-[2,6-dinitro-4-(1,2,3,4-tetrahydro-4-phenyl-1-naphthyl)phenyl]-2-(4-nitrophenyl)-2-phenylhydrazine and 9 while thermolysis of 1,2-bis(1-phenylethyl)diazene in the presence of DPPH yields 9 and 44% of 1-[2,6-dinitro-4-(1-phenylethyl)phenyl]-2,2-diphenyl-hydrazine showing that substituted benzyl radicals efficiently displace the 4-nitro group of DPPH. The nitro group is transferred to an unsubstituted phenyl group of DPPH.
Free energies and entropies of transfer of hydrogen halides from water to aqueous solutions of tetrahydrofuran, dioxane, and 1,2-dimethoxyethane and the structuredness of the solvents
Authors: Datta Jayati , Kundu Kiron K.
Published: May 2006

Standard free energies (ΔGt0) and entropies (ΔSt0) of transfer of hydrogen iodide from water to some aqueous solutions of tetrahydrofuran (THF), dioxane (D), and 1,2-dimethoxyethane (DME) have been determined by measuring the emf's of the cell: Pt, H2 (g, 1 atm)|KOH (m1), KI (m2), solvent|AgI, Ag at seven equidistant temperatures ranging from 5 to 35 °C. In each of these ethereal solvent systems ΔGt0 values of HI, as well as of HCl and HBr obtained from the literature, and particularly of the individual ions, suggest that while H+ is increasingly stabilized, halide ions are increasingly destabilized due to the influence of cosolvent-induced larger "basicity" and smaller "acidity" of the mixed solvents compared to that of water, and both conformed to the expected order: D < THF < DME. Moreover, the relative order: Cl− > Br− > I− in all the solvent systems is ascribable to the combined effects of "acid–base" and "soft–soft" interactions and the superimposed quadrupolar interactions in the case of D and the charge transfer to solvent (CTTS) complexation effect, especially on I− in the case of THF. Analysis of the entropie contributions, TΔSt0, and particularly of the relative order of ΔY (≡TΔSt0(H+) + TΔSt,ch0(X−)) for X = Cl, Br, and I, in the light of the semi-quantitative theory proposed earlier by Kundu et al., reveals that at initial compositions, while THF promotes 3D structures of water, both D and DME break down the same; at higher compositions all the cosolvents disrupt the structure as usual due to packing imbalance. The nature and relative positions of ΔY–composition profiles also suggest that while increase of hydrophobic groups of the cosolvents increases the stabilization, increase in hydrophilicity or H-bonding sites decreases the stabilization of the 3D structure of water.
Conformational effects on the enthalpy of formation of straight and branched-chain alkanes
Authors: Edward John T.
Published: May 2006

Benson's scheme for calculating the enthalpy of formation of straight and branched-chain alkanes by addition of increments for methyl, methylene, methine, and quaternary carbon groups, and by correction (where necessary) for steric effects, has been modified by a more detailed consideration of the effect of gauche interactions.
The electroreduction of aromatic aldehydes in aprotic solvents
Authors: Fawcett W. Ronald , Lasia Andrzej
Published: May 2006

The mechanism of electroreduction of aromatic aldehydes was investigated by cyclic voltammetry in dimethylformamide and acetonitrile in the presence of tetraethylammonium, potassium, and sodium perchlorates. It was found that the reaction products disappear in a dimerization reaction. Rate constants for the subsequent dimerization and association constants for ion pair intermediates were determined. The reactivity of the anion radicals initially formed decreases in the sequence: 9-anthraldehyde > benzaldehyde > 2-naphthaldehyde > 1-naphthaldehyde. The Hückel molecular orbital method was used to explain the reactivity sequence and the properties of the radical intermediates.
Separation of fluorescent impurities from Amphotericin B
Authors: Petersen Nils O. , Henshaw Paul F.
Published: May 2006

Reverse phase high pressure liquid chromatography of Amphotericin B samples provides one means of cleanly separating Amphotericin B from a strongly fluorescent contaminant. Purified Amphotericin B does not exhibit any fluorescence.
Semiempirical HAM/3 calculation of valence-electron shake-up satellite bands in the ionization spectra of CO2, N2O, and C2F4
Authors: Chong Delano P.
Published: May 2006

Valence-electron shake-up satellite bands in the ionization spectra of carbon dioxide, nitrous oxide, and tetrafluoroethene have been calculated with a modified version of the HAM/3 program. The results are compared with experiment and with the computations based on two-particle-hole Tamm-Dancoff approximation Green's function method. Because of the limitation of such Green's function procedures for inner-valence electrons, the results can often be inferior to those from the present HAM/3 calculations.
Reactions of sydnones. Part III. Bromination of 3-[p-(1′-pyrazolyl)]phenylsydnone
Authors: Havanur Shambhuling B. , Badami Bharati V. , Puranik Gurubasav S.
Published: May 2006

3-[p-(1′-Pyrazolyl)]phenylsydnone (2) and its derivatives have been subjected to bromination in order to study the relative reactivities of the sydnone and pyrazole moieties. The products have been confirmed by their elemental analysis and their spectral data.
Synthesis of 4-hydroxy-3,4-dihydro-1,2,3-benzotriazines via 2-(3-alkyl-1-triazeno)benzaldehydes and 2-(3-alkyl-1-triazeno)benzophenones
Authors: Faye Patricia L. , Vaughan Keith , Hooper Donald L.
Published: May 2006

Diazotization of o-aminobenzaldehyde, followed by immediate coupling of the diazonium salt with primary alkylamines, affords unstable l-aryl-3-alkyltriazenes which immediately cyclize to the 4-hydroxy-3-alkyl-1,2,3-benzotriazines. Analogous reaction of o-aminobenzophenones affords stable 4-aryl-4-hydroxy-3-alkyl-1,2,3-benzotriazines. The 4-hydroxytriazine derived from o-anthraniloylbenzoic acid undergoes further cyclization spontaneously to a novel spiro-1,2,3-triazine-furan. Diazotization of o-aminopropiophenone and coupling to methylamine affords a surprisingly stable 4-alkyl-4-hydroxytriazine. Preliminary assay of the biological activity of the 4-hydroxytriazines shows significant cytotoxicity of two members of the series towards M21 melanoma cells in vitro.
Crystal structure of N,N′-dimethyl-2-imidazolidinethione, a by-product from the reaction of Na2(CH2N(CH3)CS2)2 and HgCl2
Authors: Chieh Chung , Cheung Sing Kwen
Published: May 2006

The reaction between mercury (II) chloride and N,N′-dimethylethylenebisdithiocarbamate gave a white precipitate. In an attempted recrystallization from an aqueous–ethanol solution, a cyclic thiourea-type compound, N,N′-dimethyl-2-imidazolidinethione, was obtained. The crystals of this compound are monoclinic, a = 10.388(2), b = 6.139(1), c = 12.291(4) Å, β = 118.64(2), and space group P21/c. The non-hydrogen atoms of the molecule are planar and the C=S bond length is 1.673(4) Å. The structure was refined by full-matrix least-squares from 642 independent reflections measured on an automatic diffractometer to R and Rw of 0.053 and 0.068, respectively.
The probable planarity of 1,2-dimethoxybenzene in solution
Authors: Schaefer Ted , Laatikainen Reino
Published: May 2006

A precise analysis of the 1H nmr spectrum of 1,2-dimethoxybenzene in benzene solution yields an accurate value for the proximate spin–spin coupling constant, [Formula: see text], between the ortho ring proton and the methyl protons. The latter also couple to other ring protons and these couplings are assessed. Comparison with some values in other anisole derivatives and with a variety of INDO MO FPT calculations of [Formula: see text] strongly implies the predominance of a planar conformation in solution. This implication disagrees with the interpretation of some other experimental and theoretical data. The mechanism of this proximate coupling is examined by the procedure of Barfield. It seems that the magnitude of the coupling is dominated by interactions involving the orbitals on the carbon atom of the methyl group.
Betylates. 4. The synthesis and preparative nucleophilic substitution reactions of alkyl S-[3]betylates
Authors: King James Frederick , Skonieczny Stanislaw , Poole Gary Allan
Published: May 2006

Alkyl S-[3]betylates (S,S-dialkyl-S-3[(alkyloxy)sulfonyl]propylsulfonium salts), the first examples of S-betylates (sulfonioalkanesulfonic esters), have been synthesized by two routes, and their suitability as intermediates in the transformation of alcohols by nucleophilic substitution reactions examined. They have been found to react readily in stoichiometric phase transfer processes, including substrate–reagent ion-pair reactions, like their previously studied nitrogen analogues, with the following particular features: (a) they may be used with basic nucleophiles (unlike [2]betylates), (b) they are more simply made from commercially available starting materials than [3]betylates, and (c) they can be made by a route that avoids a final alkylation step.
Selective transformations of secologanin: epoxidation
Authors: Saunders Gavin N. , Purdy John R. , McLean Stewart
Published: May 2006

The oxidation of tetraacetylsecologanin dimethyl acetal (7) by m-chloroperbenzoic acid has been studied and the results have been compared with those obtained when tetraacetylsweroside was oxidized by the same reagent. Complete site selectivity for the vinyl side chain and a relatively low stereoselectivity leading to the formation of a small excess (7:2) of the epoxide with the 3-R configuration was observed with the sweroside derivative. These results parallel those in the osmium tetraoxide oxidation, and the configurations of the glycols produced have been correlated chemically with those of the epoxides. In contrast, there is little site selectivity in the oxidation of the secologanin derivative; in fact, it is the β-alkoxyacrylate site that appears to be oxidized faster to produce an epoxide (9) that then undergoes a second epoxidation at the vinyl side chain. Stereoselectivity is complete in the first epoxidation and is high in the epoxidation of the vinyl side chain, leading to the isomer with the 3-R configuration as the major product. The site selectivity appears to parallel that observed in dihydroxylation of the secologanin derivative, but the stereoselectivity of oxidations at the vinyl side chain is opposite in the two series; the configurations of the glycols and epoxides have been correlated chemically. A rational explanation can be advanced for the observed stereoselectivity in every case, but no convincing argument to explain the observed differences in site selectivity has been found.
Photochemically initiated addition of alcohols to ketones: facile photoketalization of cycloalkanones
Authors: Malatesta Vincenzo , Jennings Michael , Hackett Peter
Published: May 2006

Irradiation at 300 nm of cycloalkanones in methanol gives the corresponding ketals in good yields. The results indicate that an excited state of the cycloalkanone is responsible for the facile addition of methanol to the carbonyl group.
Formation equilibria of silver amminocomplexes at temperatures up to 453 K
Authors: Kołodziej Barbara
Published: May 2006

The formation equilibria of silver amminocomplexes were investigated by potentiometric method over the temperature range 333 to 453 K. On the grounds of emf measurements of a concentration cell consisting of[Formula: see text]the equilibrium concentrations of uncomplexed silver ions [Ag+] were determined in a Ag—NH3—H2O system. The Leden method was followed and the mean number of ligands [Formula: see text] per silver atom bound in amminocomplexes as well as the equilibrium concentration of free ammonia [NH3] were calculated. From the values obtained above the stability constants of silver amminocomplexes β1 and β2 were determined over the temperature range 333 to 453 K. The dependence of log β1 versus temperature was described by the equation: log β1 = 6.89 − 1.16 × 10−2 T whereas for log β2 the linear equation: log β2 = 14.10 − 2.41 × 10−2 T is satisfied only up to 413 K. Above 413 K the nature of the dependence is changed.
Fractionation of lignosulphonates released during the early stages of delignification
Authors: Lewis Norman G. , Goring David A. I. , Wong Alfred
Published: May 2006

High-yield spent bisulphite liquor (HY-SBL) from sulphonated black spruce wood (Piceamariana) was fractionated by gel permeation chromatography (GPC) and by high-performance liquid chromatography (HPLC). The GPC fractionation gave a wide bimodal distribution, whereas with HPLC, a more detailed resolution was seen with the bulk of the fraction giving several clearly defined peaks. The paucidisperse material was further concentrated by a bulk fractionation of the crude SBL which included complexing the lignosulphonates with dicyclohexylamine. The isolated paucidisperse material was found to be dialyzable and to constitute 90% of the lignosulphonate in the sample of SBL. If the bisulphite pulp obtained was recooked in fresh acid sulphite liquor to a lower yield, most of the lignosulphonate dissolved was widely polydisperse with no indication of the discrete components resolvable by HPLC. However, 25% of the lignin made soluble was in the form of the paucidisperse fractions. In all, we were able to obtain about 50% of the lignin in spruce wood as a relatively low molecular weight lignosulphonate resolvable into discrete fractions by HPLC.
Conformation of azaphosphorinane ring. Crystal structures of 2,2,6,6-tetramethyl-4,4-diphenyl-1,4-azaphosphorinanium perchlorate and 2,2,6,6-tetramethyl-4-oxo-4-phenyl-1,4-azaphosphorinan-1-oxyl (stable nitroxy radical)
Authors: Cygler Miroslaw , Skolimowski Janusz
Published: May 2006

Crystal structures of 2,2,6,6-tetramethyl-4,4-diphenyl-1,4-azaphosphorinanium perchlorate (I) and 2,2,6,6-tetramethyl-4-oxo-4-phenyl-1,4-azaphosphorinan-1-oxyl (II) were determined. Compound I crystallizes in the monoclinic space group C2/c with unit cell dimensions a = 18.2967(7), b = 10.9413(6), c = 20.8714(13) Å, β = 90.79(1)° (at 115 K), and II crystallizes in the orthorhombic space group Pn21a with a = 8.076(1), b = 10.139(1), c = 17.894(1) Å. Intensity data were measured on a diffractometer at 115 K for I and at the room temperature for II. The structures were solved by a combination of heavy-atom and direct methods and refined to R = 0.036 (3968 reflections) for I and 0.039 (1451 reflections) for II.The azaphosphorinane ring adopts a chair conformation in both molecules, being flattened in the P part in I and in the N part in II. In molecule I the equatorial phenyl group is nearly parallel to the approximate plane of symmetry of the molecule, and the axial phenyl group is perpendicular to that plane. In molecule II the P=O bond is axial and the phenyl group is equatorial. The CN(O)C group is not planar. The N—O bond makes an angle of 18.0(3)° with the CNC plane. The CNC angle of 129.3(3)° is larger than that found in nitroxypiperidine analogues.
Synthèses et epimérisation de déoxy-spiro C-1 sucres
Authors: Remy Georges , Cottier Louis , Descotes Gérard
Published: May 2006

2-Deoxy and 2,3-dideoxy-3-oxo-butyl-β-D-glycopyranosides were synthesized starting from tri-O-acetyl-D-glucal. These β compounds undergo Norrish II type photocyclization giving the corresponding hydroxyspiroketals without stereoselectivity but with greater reactivity than the α derivatives. Acidic epimerization of these spiro C-1 sugars leads to the α anomers in accord with known stereoelectronic effects.
Sedum alkaloids. V. Sedacrine, the major alkaloid of Sedumacre, and related bases
Authors: Colau Brigitte , Hootelé Claude
Published: May 2006

Sedacrine, the major alkaloid of Sedumacre, is assigned structure 5 on the basis of spectroscopic and chemical evidence. Two minor bases, sedinone 6 and dihydrosedinine 7, are described. Sedacrine 5, sedinone 6, dihydrosedinine 7, and sedinine 3 are correlated. The absolute configurations of these alkaloids and that of sedacryptine 2 are established.
The chlorination of dihydroconiferyl alcohol
Authors: McKague A. Bruce , Rettig Steven J. , Trotter James , Douglas George R. , Nestmann Earle R.
Published: May 2006

Aqueous chlorination of dihydroconiferyl alcohol, a phenol present in pulping liquors, gave a mixture of three products. The two major products, which formed an inseparable mixture, yielded the crystalline epoxides 1 and 8 when reacted with diazomethane. The epoxide 1 had previously been obtained by reacting one of the components isolated from mutagenic fractions of chlorination-stage effluent from a bleached kraft pulp mill with diazomethane. The results indicate dihydroconiferyl alcohol retained with pulp is chlorinated in the bleach plant to give a mixture of the spirocyclohexenediones 5 and 6. Crystals of 8 are orthorhombic, a = 24.3048(15), b = 12.5403(9), c = 7.8653(6) Å, Z = 8, space group Pbca. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.029 and Rw = 0.035 for 1308 reflections with I ≥ 3σ(I). The structure analysis shows that 8 has the same relative stereochemistry as that reported earlier for 1, but exists as a different conformer in the solid state.
Stereospecific vicinal oxyamination of N-substituted 1,2,3,6-tetrahydropyridines and 1,2-dihydropyridines by N-chloro-N-metallocarbamates
Authors: Dubey Sushil K. , Naus Edward E. K.
Published: May 2006

The vicinal oxyamination of 1-substituted 1,2,3,6-tetrahydropyridines (2) affords a mixture of the regioisomeric cis-hydroxycarbamates 3 and 4. The tert-butoxycarbonylamino and hydroxyl substituents for 3 and 4 assume the equatorial and axial orientations respectively, irrespective of the substituent position. Acid hydrolysis of 3a and 4a affords the cis-aminoalcohols 5 and 6. The regiospecific oxyamination of 1-methyoxycarbonyl-1,2-dihydropyridine occurs at the 5,6-olefenic bond to yield the hydroxycarbamates 15 and 16. Reduction of 15 or 16 with palladium on charcoal affords the same vicinal hydroxy and methoxycarbamates 17 to 20 which may arise via the aziridine intermediate 21.
Nuclear analogs of β-lactam antibiotics. XVI. Aldol condensations of N-protected 4-tritylthio-2-azetidinones
Authors: Martel Alain , Collerette Jean , Banville Jacques , Daris Jean-Paul , Lapointe Philippe , Belleau Bernard , Ménard Marcel
Published: May 2006

The reaction of acetaldehyde with enolates of N-protected 4-tritylthio-2-azetidinones 4b and 4c was studied. While the lithium enolate of N-methoxymethylazetidinone 4b gave only transS* 3-(1′-hydroxyethyl)azetidinone 8 the corresponding tetrabutylammonium enolate gave a mixture of transR* and transS* azetidinones 8 and 9. The metal enolate of N-(tert-butyldimethylsilyl)-4-tritylthio-2-azetidinone 4c gave all four possible isomers.
Total synthesis of the C-3 – C-17 segment of boromycin
Authors: Hanessian Stephen , Delorme Daniel , Tyler Peter C. , Demailly Gilles , Chapleur Yves
Published: May 2006

The C-3 – C-17 segment of boromycin having five asymmetric centers was synthesized from D-arabinose and D-glucose as chiral precursors. Constitutional and stereochemical identity was established by comparison of the synthetic product with a sample obtained from the degradation of the antibiotic.
Heavy target fragment yields in the interaction of 28 GeV protons with 238U
Authors: Jacak B. V. , Loveland W. , Morrissey D. J. , McGaughey P. L. , Seaborg G. T.
Published: May 2006

The yields of target fragments from the interaction of 28 GeV protons with 238U have been measured, with special attention being given to those fragments with 160 ≤ A ≤ 200. From the measured fragment yields, isobarie production cross sections were calculated. Significant yields (σ(A) ~ 1–10 mb) of heavy target fragments (160 ≤ A ≤ 210) were found. These fragments are believed to be the non-fissioning survivors from the population of highly excited residual nuclei produced in the initial p-nucleus collision. A pedagogical calculation of the fission – particle emission competition shows how the initial highly excited heavy nuclei could evaporate ~20–50 particles while surviving fission competition.
The synthesis of bridged biphenyl and naphthyl compounds by the photolytic and thermal extrusion of SO2
Authors: Harpp David N. , Mullins Dennis F.
Published: May 2006

The photolytic and flash vacuum thermolytic behavior of several SO2-containing cyclic compounds was studied. The expulsion of SO2 by flash vacuum thermolysis afforded the corresponding bridged compounds in high yield.
Radical cations of strained ring hydrocarbons. Cyclopropane derivatives
Authors: Roth Heinz D. , Schilling Marcia L. Manion
Published: May 2006

A series of radical cations has been generated from various cyclopropane derivatives by photoinitiated electron transfer to chloranil. Nuclear spin polarization effects observed during these reactions have been interpreted as evidence for the structure of these intermediates. Tri- and tetraalkylsubstituted cyclopropanes (1, 3, 4) form "trimethylene" radical cations in which the most highly substituted carbon–carbon bond is broken (or weakened). The benzocyclopropanorbomene (12) forms a radical cation in which spin and charge are located in the benzenoid ring; the tertiary cyclopropane protons are coupled by a homohyperconjugative interaction; otherwise, the cyclopropane ring is unaffected. To the radical cation derived from bis-methanoparacyclophane (17) a trimethylene structure is assigned in which the benzylic carbons are pyramidal. Finally, benzonorcaradiene (20) forms a radical cation in which the two secondary–tertiary bonds are lengthened and in which the methylene group bears spin density.
Preparation of some deuterium labelled 9- and/or 10-oxygenated derivatives of geraniol, geranial, nerol, and neral
Authors: Balsevich J.
Published: May 2006

The preparation of various deuterium labelled 9- and/or 10-oxygenated derivatives of geraniol, geranial, nerol, and neral is described. Wittig reaction of the tetrahydropyranyl ethers of (E)- and (Z)-1,1-dideutero-6-(triphenylphosphonium)-3-methyl-2-hexen-1-ol iodides (23 and 24) with the tetrahydropyranyl ethers of hydroxyacetone and 1,3-dihydroxyacetone afforded, after deprotection, C-1 dideuterated 9-hydroxygeraniol, 9-hydroxynerol, 9,10-dihydroxygeraniol, and 9,10-dihydroxynerol of high isomeric purity. Selective oxidation of these products allowed for the preparation of the corresponding derivatives possessing an aldehyde functionality at C-9 or C-1 and C-9. Wittig reaction of 23 and 24 with pyruvaldèhyde dimethyl acetal followed by acidic hydrolysis afforded C-1 dideuterated 10-oxogeraniol and 10-oxonerol, oxidation of which yielded C-1 deuterated 10-oxogeranial and 10-oxoneral. Wittig reaction of (E)- and (Z)-1,1-dideutero-6-(triphenyl-phosphonium)-3-methyl-2-hexen-1-ol iodides (49 and 50) with 1,1,3,3-tetraethoxyacetone afforded C-1 dideuterated 9,9,10,10-tetraethoxygeraniol and 9,9.10,10-tetraethoxynerol, oxidation of which provided C-1 deuterated 9,9,10,10-tctraethoxygeranial and 9,9,10,10-tetraethoxyneral.
Purine complexes of platinum: synthesis, nmr, and crystal and molecular structures of cis-chloro(caffeine)bis(triethylphosphine)platinum(II) fluoroborate and cis-bis(isocaffeine)bis(triethylphosphine)platinum (II) fluoroborate
Authors: Bushnell Gordon William , Densmore Roderick James , Dixon Keith Roger , Ralfs Arthur Charles
Published: May 2006

Synthesis and 31P nmr spectra of the complex cations, cis-[PtCl(L)(PEt3)2]+, L= theophylline, caffeine, or isocaffeine, and cis[Pt(isocaff)2(PEt3)2]2+ are reported. The crystal structure of cis-[PtCl(caffeine)(PEt3)2][BF4] is determined, space group [Formula: see text], a = 1.1766(6), b = 1.4428(5), c = 0.9002(4) nm, α = 97.28(4)°, β = 97.69(4)°, γ = 100.96(5)°, Dm = 1.649 g cm−1, the bond lengths are Pt—Cl= 233.4(4) pm, Pt—N = 215(1) pm, Pt—P = 225.4(5) pm (mean), and the residual R = 0.071. The crystal structure of cis-[Pt(isocaffeine)2(PEt3)2][BF4]2 is orthorhombic, space group Pbca, a = 2.317(3), b = 1.717(3), c = 2.130(3) nm, Dm = 1.574 g cm−3, with an opposing isocaffeine conformation, bond lengths Pt—N = 211(2) pm, Pt—P = 227.6(9) pm (mean), and R = 0.073. Both crystal structures contain approximately square planar Pt(II) coordination with the purine coordinated via an imidazole nitrogen. The structures are discussed as models for the possible involvement of [Formula: see text] chelation of guanine to platinum when platinum drugs act as antitumour agents, but there is no evidence that isocaffeine acts as an [Formula: see text] chelate.
The reaction of 1,6,6aλ4-trithiapentalenes with carbene and nitrene reagents
Authors: McKinnon David M.
Published: May 2006

The reaction of some 1,6,6aλ4-trithiapentalenes with ethyl azidoformate provides 1:1 adducts, formulated as 4-thioacyl-methylene-1,3,2-dithiazine-2-carboxylic esters; and with diphenyldiazomethane, 1:2 adducts, formulated as 4-(3-propenylidene)-1,3-dithiins. In some cases 4-diphenylmethylenethiopyrans are isolated. The products arise by insertion at a disulfide type bond, or on a thione function of an initial reaction product.
Échelle d'acidité dans les mélanges eau–oxydipropionitrile. II. Cas des mélanges eau–oxydipropionitrile. Application à l'extraction
Authors: Gal J. Y. , Persin M. , Castelas B.
Published: May 2006

The study of acid–base reactions in water–oxydiproprionitrile mixtures using glass and hydrogen electrodes allows for the determination of the pKa for some couples in these media. It then becomes possible to develop buffers capable of fixing the acidity level in mixtures undergoing separation during demixtion. The extraction with oxydiproprionitrile of various acids, bases, chelating agents shows that the yields are greatly influenced by the nature of the ions present in the aqueous phase. Knowing the transfer parameters of the various species is an important factor in orienting the research for the most favorable extraction conditions. [Journal translation]
Coordinence 2 du phosphore: étude quantochimique des systèmes P=N et P=C
Authors: Gonbeau D. , Pfister-Guillouzo G. , Barrans J.
Published: May 2006

Using abinitio valence double zeta as a basis, a quantum-chemical approach was developed for the models HP=NH and PH=CH2. The geometric parameters were determined by a variable metrics minimization process.The 2pπ–3pπ bond forces for P=N and P=C were estimated by evaluating the barriers obtained by a 90° rotation of one part of the molecule with respect to the other. The essential correlation effect was considered and a rigourous RHF formalism was used to determine the state at 90° of lower energy.Different electronic characteristics were found for both motives and according to these results, their reaction behaviour was interpreted: dimerization, addition of polar reactants, and protonation site for HP=NH.
Synthesis of Mannich bases from electrochemically generated iminium salts in the presence of silyl enol ethers
Authors: Renaud Roger N. , Bérubé Denis , Stephens Campbell J.
Published: May 2006

The formation of Mannich bases from the reaction of silyl enol ethers with N-methyl-N-mesitylmethyleniminium salt, generated by the electrochemical oxidation of N,N-dimethylmesidine, was studied. Important factors influencing the reaction are: (a) the silyl enol ether must be nucleophilic enough to react with the iminium salt and, at the same time, must be more difficult to oxidize than the tertiary amine, (b) the product of the reaction must not be oxidized at the operating potential. Examples are presented in this paper illustrating the successes and limitations of this reaction.
Syntheses of optically active 2-tetrahydrofuran derivatives
Authors: Bélanger Patrice C. , Williams Haydn W. R.
Published: May 2006

The resolution of 2-tetrahydrofuran-carboxylic acid and assignment of configuration to the enantiomers are reported. New syntheses of the enantiomers of 2-tetrahydrofurancarboxaldehyde are also described.
The monoblocking of symmetrical diketones on insoluble polymer supports
Authors: Xu Zhang-Huang , McArthur Colin R. , Leznoff Clifford C.
Published: May 2006

A 1% crosslinked divinylbenzene–styrene copolymer, incorporating vicinal diol groups or their isopropylidenc precursors, was used to form the monoacetals of the symmetrical diketones, p-diacetylbenzene, 1,2-cyclohexanedione, 1,3-cyclohexanedionc, 1,4-cyclohexanedione, and 2,5-hexanedione. The free ketone groups reacted with phenylmagnesium bromide to give, in high yield, after acid hydrolysis from the polymer, the expected products such as 3-phenyl-2-cyclohexen-1-one from 1,3-cyclohexanedione. The 13C nmr spectra of some polymer-bound substrates and simple analogs are described.
Organic sulfur mechanisms. 24. Preparation and reactions of 2-hydroxyethanesulfonyl chloride, the first hydroxyalkanesulfonyl chloride
Authors: King James Frederick , Hillhouse John Henry
Published: May 2006

2-Hydroxyethanesulfonyl chloride (1a) is readily made by reaction of an aqueous solution of 2-mercaptoethanol (4a) with chlorine. This is the first clearly proved preparation of a compound which is both an alcohol and a sulfonyl chloride. Reactions of 1a with water and alcohols evidently proceed largely by intramolecular cyclization to the transient β-sultone (2a), which then undergoes nuclcophilic ring opening to form the products. In the presence of tertiary amines a minor but significant part of the reaction is shown by deuterium labelling to proceed via hydroxymethylsulfene (14). the principal reaction of which is simply to add the alcohol or water; only a small part, if any, of the sulfene (14) loses the hydroxy¡ group to give the ethenesulfonate derivatives (13 or 22). Aqueous chlorination of 3-mercapto-1-propanol gave 3-chloro-1-propanesulfonyl chloride (5a) and 1,3-propane sultone (2b) with no sign of any 3-hydroxy-1-propanesulfonyl chloride (1b). A mechanism for the aqueous chlorination process invoking a cyclic chlorooxasulfoxoniuin ion (27) is discussed.
Dynamic stereochemistry of 2,3,12,13-tetrathia- and -tetraselena[4,4]metacyclophanes
Authors: Dixon Keith R. , Mitchell Reginald H.
Published: May 2006

2,3,12,13-Tetrathia- and –tetraselena[4,4]metacyclophanes exhibit temperature dependent 1H nmr spectra in which the methylene resonances change from AB spectra in the low temperature limit to singlets at higher temperatures. Coalescence temperatures are 256 and 208 K, respectively, and a complete line-shape analysis yields [Formula: see text] and [Formula: see text]. The spectra and thermodynamic data are interpreted in terms of a mechanism involving interconversion of syn conformers with little or no involvement of the anti conformers previously assumed to dominate in this type of molecule.
Model compounds for biodegradation studies on hydrocarbon-type dielectric fluids
Authors: Baarschers Willem Hendrik , Li Maria Angela
Published: May 2006

The hydrocarbons 7-methylpentadecane (1, n = 0) and 7-methyl-9-n-hexyl heptadecane (1, n = 1) have been synthesized. These compounds arc suitable as model compounds for biodegradation studies on mixtures of oligomers of 1-oetene and related compounds which have been proposed as dielectric fluids for the replacement of PCB's. The synthesis confirms the feasibility of isotope labelling for such biodegradation studies.
Synthesis and crystal structure analysis of trichloro(dimethylformamide)bis(dimethylsulfoxide)rhodium(III)
Authors: Rochon F. D. , Kong P. C. , Melanson R.
Published: May 2006

mer-[Rh(DMSO)2(DMF)Cl3] was prepared by dissolving [Rh(DMSO)3Cl3] in dimethylformamide (DMF). It forms monoclinic crystals, a = 11.530(3), b = 8.971(2), c = 15.912(3) Å, β = 107.88(2)°, Z = 4, and space group P21/c. The structure was refined by full-matrix least-squares analysis to a conventional R factor of 0.038 (3495 observed reflections).The coordination around the Rh atom is octahedral. The compound is the peripheral or the 1,2,6-isomer. The DMF molecule is in trans position to a DMSO ligand and bonded to rhodium through the oxygen atom. The two molecules of DMSO are bonded to rhodium through sulfur. The Rh—Cl(1) bond (2.366(1) Å) trans to a DMSO molecule seems slightly longer than the two Rh—Cl bonds trans to each other (2.329(1) and 2.343(1) Å).
The stationary-state approximation in the photolysis of acetone
Authors: Nicholson A. J. C.
Published: May 2006

A mechanism has been written for the photolysis of acetone at 313 nm and 253.7 nm and the differential equations involved solved rigorously. Testing this mechanism has revealed inconsistencies between different sets of experiments that were not previously obvious. The stationary-state approximation is valid up to ca. 0.5% decomposition but its practical usefulness is minimal. Graphs are given showing the variation of all significant quantum yields with temperature, pressure, and light intensity.
Lanostane-to-cucurbitane transformation
Authors: Edwards O. E. , Paryzek Z.
Published: May 2006

Westphalen-type rearrangement of a 9α-hydroxy-11-ketone derived from lanosterol resulted in formation of two 19(10 → 9β)abeo-lanostenes representing the first lanostane-to-cucurbitane transformation. A novel ring A aromatic 9,10-seco derivative was formed as an acid catalysed cleavage product of 11-keto cucurbitenes. A cine 9 → 12 substitution led to the first 12-substituted lanostane derivatives and the first C-nor-D-homolanostane derivatives.
Chemical studies on oils derived from aspen poplar wood, cellulose, and an isolated aspen poplar lignin
Authors: Eager Richard L. , Pepper James M. , Roy Jiben C. , Mathews Joseph F.
Published: May 2006

An initial study has been made of the chemical nature of the oil phase resulting from the the conversion of aspen poplar wood, cellulose, and an isolated lignin from the aspen poplar as a result of their interactions with water and carbon monoxide in the presence of sodium carbonate at 360 °C. Gas chromatographic analysis of the sodium hydroxide soluble fractions from each substrate revealed similar spectra of alkyl-substituted phenols. The relative abundance of identified low molecular weight phenolic compounds decreased from lignin to wood to cellulose. This was in agreement with the known phenolic nature of lignin. As well, it confirmed the synthesis during reaction of such compounds from a carbohydrate substrate. Gas chromatographic analysis of the whole oils also revealed the presence in each case of several alkyl-substituted cyclopentanones whose relative abundance decreased from cellulose to wood to lignin. Silica gel column separation of the oils, after a charcoal treatment, followed by capillary gas chromatographic – mass spectrometric analyses of the resulting fractions indicated the presence of other higher molecular weight phenols, napthols, cycloalkanols, cycloalkanones, and polycyclic and long chain alkanes and alkenes.
Absolute rate constants for hydrocarbon autoxidation. 33. A product study of the self-reaction of α-tetralylperoxyls in solution
Authors: Baignée A. , Chenier J. H. B. , Howard J. A.
Published: May 2006

The major initial products of the self-reaction of α-tetralylperoxyls (C10H11O2•) in chlorobenzene at 303–353 K are equal concentrations of α-tetralol and α-tetralone in ~90% yield based on the number of initiating radicals. These yields are consistent with the non-radical (Russell) mechanism for self-reaction. Low concentrations of bis(α-tetralyl) peroxide are produced, indicating that there is a small but detectable free-radical contribution towards termination. C10H11O2• undergoes β-scission in this temperature range but steady-state concentrations of C10H11• are too low to influence the termination rate constant 2kt, or react with C10H11O2• to give (C10H11O2. α-Tetralol to α-tetralone ratios and total yields of these products are significantly less than 1 and 100%, respectively, in methanol and acetonitrile. Formaldehyde is produced in methanol indicating the involvement of α-hydroxymethylperoxyls, derived from the solvent, in termination. There is no evidence for a chain reaction or a zwitterion intermediate for self-reaction of C10H11O2• in solution.
Low-temperature infrared studies of some acid–base reactions
Authors: Huston Theresa , Hisatsune I. C. , Heicklen Julian
Published: May 2006

Low-temperature infrared spectroscopy has been used to examine the systems NH3 + H2O, NH3 + HCl, H2O + HCl, NH3 + HNO3, and NH2OH + HNO3. Hydrogen-bonding in the solid states greatly reduces the reactivities in these systems. Temperatures where reactions initiated in the systems NH3(s) + HCl(g), HNO3(s) + NH3(g), H2O(s) + HCl(g), and NH2OH(s) + HNO3(s) were, respectively, −145, −130, −127, and −125 °C. Infrared spectra of 2NH3•H2O, NH3•H2O, NH4Cl•3NH3, NH4NO3•3NH3, NH4NO3•2HNO3, NH2OH2+NO3−, NH3OH+NO3−, H3O+Cl−, H5O2+Cl−, and H5O2+Cl−•H2O have been identified in these reaction systems.
Sulfoxydes et sulfones hétérobicycliques dérivés de l'α-thioglycérol. 2,8-Dioxa-6-oxo-6-thiabicyclo[3.2.1]octanes et 2,8-dioxa-6,6′-dioxo-6-thiabicyclo[3.2.1]octanes
Authors: Calinaud Pierre , Gelas Jacques
Published: May 2006

The oxidation reactions of heterobicyclic sulfides derived from α-thioglycerol (alkyl-2,8-dioxa-6-thiabicyclo[3.2.1]octanes), leading to sulfoxides and the corresponding sulfones, have been studied. The stereochemistry of the oxidation as a function of the reagent used (H2O2, meta-chloroperbenzoic acid, and tert-butyl hypochlorite) has been examined. Structural assignments of the sulfoxides arise from the spectroscopic and chemical properties of these compounds. [Journal translation]
On the reaction of furan with bromine in aqueous solution. Observation of the slow hydration of malealdehyde
Authors: Tee Oswald S. , Swedlund B. E.
Published: May 2006

The rate of reaction of furan with bromine in aqueous solution has been measured and the rate constant obtained by Williamson and Coller is confirmed. However, it is now found that the reaction of bromine with furan in water has two distinct stages: attack of bromine leading to the formation of malealdehyde 3 and hydration of 3 to a 2:1 mixture of the geometrical isomers of its cyclic hydrate 4. This second, slower process is observable by stopped-flow uv spectrophotometry occurring after the consumption of bromine. The observed kinetics are very similar to those recently found for the analogous hydration of phthalaldehyde by McDonald and Martin.
Equilibrium decomposition pressures of the compounds Cs2ZrCl6 and Cs2HfCl6 and X-ray identification of Na2HfCl6, K2HfCl6, and Cs2HfCl6
Authors: Kipouros G. J. , Flengas S. N.
Published: May 2006

The chemical equilibria representing the reactions[Formula: see text]and[Formula: see text]were investigated by direct vapour pressure measurements and thermodynamic data such as free energies and enthalpies of reaction have been calculated. The X-ray powder patterns of the compounds Na2HfCl6, K2HfCl6, and Cs2HfCl6 are also reported.With reference to the separation of Hf from Zr by a recently developed process based on the selective reactivity of ZrCl4 and HfCl4 vapours with alkali chlorides, it is shown that the efficiency of alkali chlorides as separating agents increases in the order CsCl → LiCl → NaCl → KCl.
Pentaketide metabolites from Potebniamycesgallicola n. sp.
Authors: Boulet Camille A. , Poulton Gerald A.
Published: May 2006

The fungus Potebniamycesgallicola n. sp. has been isolated from cankered swellings of western hemlock (Tsugaheterophylla (Raf.) Sarg.) produced by the dwarf mistletoe (Arceuthobiumtsugense (Rosendahl) G. N. Jones), and has been implicated in the induction of disease in the infected trees. P. gallicola was cultured on malt extract, and four isoprenylated pentaketide metabolites were isolated by extraction; these were identified as the known compounds fuscin 1 and dihydrofuscin 2, and two related compounds secofuscin 3 and dihydrosecofuscin 4, not previously reported in nature.
The structure of the benzene–maleimide photosynthetic product (mitindomide)
Authors: Pettit George R. , Paull Kenneth D. , Herald Cherry L. , Herald Delbert L. , Riden Joseph R.
Published: May 2006

The photochemical reaction between benzene and maleic anhydride or benzene and maleimide affords respectively anhydride 6a and imide 6b. Unequivocal structures 6a and 6b were assigned on the basis of an X-ray crystal structure determination of amide 5 derived from imide 6b. Because of pronounced activity (e.g., PS T/C 206 at 50 mg/kg) against several of the U.S. National Cancer Institute's key experimental tumor systems, imide 6b has been designated mitindomide and is being prepared for eventual clinical trial.
Charge distributions and chemical effects. XXXII. Energies of multiple carbon–carbon bonds
Authors: Fliszár S.
Published: May 2006

Bond energies are derived from total (nuclear–electronic and nuclear–nuclear) potential energies involving the individual nuclei of a molecule. It appears that the carbon–carbon bond energies in ethane, ethylene, allene, acetylene, and benzene are in a ratio of 1:2:1.9:2.9:1.6. This result enables a rapid estimate of approximate atomization energies of unsaturated hydrocarbons from those of their corresponding saturated parent compounds and, more importantly, shows the links relating to one another the various classes of saturated and unsaturated hydrocarbons in a unifying fashion.
Thallimetric oxidations. Part II Titrimetric and spectrophotometric methods for the determination of oxalate
Authors: Sagi S. R. , Rao K. Appa , Rao M. S. Prasada
Published: May 2006

Titrimetric and spectrophotometric methods are developed for the estimation of oxalate at mmole and micromole ranges, respectively. In these methods thallium(III) is used as the oxidant and the reduced thallium(I) is determined oxidimetrically by potassium bromate in the titrimetric method and by measuring the optical density of thallium (III) at 260 nm in the presence of 0.1 M HCl and 1 M HClO4 in the spectrophotometric method. A series of photochemical and thermal redox methods are described for the estimation of oxalate in the presence of a number of carboxylic acids.
Permanganate peroxidation of cyclohexene.I. The unusual effect of turbulent stirring and dilution upon glycol yields
Authors: Taylor Jay E. , Williams David , Edwards Kenneth , Otonnaa Donald , Samanich David
Published: May 2006

Yields of cis-1,2-cyclohexanediol formed by the reaction of methanol–water solutions of potassium permanganate with cyclohexene varied from nearly zero to a high of 84% as a function of stirring efficiency and dilution. This unusual effect is attributed to the formation of an intermediate hypomanganate ester ion which after formation may undergo reaction [1] with water to form the glycol or [2] with excess MnO4− to form higher oxidation products. The factor of increased stirring and dilution reduced localized excess of MnO4− and, thereby, minimized the contribution of reaction [2]. Addition of modest concentrations of methanol increased the yield, and this is attributed to enhanced solubilization and dispersion of the insoluble cyclohexene. Sodium hydroxide was beneficial to the reaction but only in low concentrations.
Uracil analogues of the acyclonucleoside 9-[[2-hydroxy-1-(hydroxymethyl)ethoxy]- methyl]guanine (BIOLF-62)
Authors: Ogilvie Kelvin K. , Hamilton Raymond G. , Gillen Michael F. , Radatus Bruno K. , Smith Kendall O. , Galloway Karen S.
Published: May 2006

A series of substituted uracil analogues of the antiviral agent 9-[[2-hydroxy-1(hydroxymethyl)ethoxy]methyl]guanine (BIOLF-62) has been synthesized and characterized. The uracil analogues show little activity against herpesviruses.
Correlation of 13C and 15N nuclear magnetic resonance chemical shifts with polarographic reduction potentials of para-substituted benzenediazonium salts and their electronic structures
Authors: Elofson R. M. , Cyr N. , Laidler J. K. , Schulz K. F. , Gadallah F. F.
Published: May 2006

Carbon-13 and nitrogen-15 nmr chemical shifts of benzenediazonium salt and its para-substituted derivatives have been measured in sulfolane solutions. The chemcial shifts of 13C1 correlate linearly with the polarographic half-wave potentials. This relation indicates the linear increase of electron densities at C1 with the increase of electron-donating power of the substituents. Non-linear relationships between 15N shifts of both nitrogen nuclei and the half-wave potentials were partly attributed to the second-order paramagnetic contributions to the 15N shifts. This contribution is approximately proportional to the inverse of the uv absorption frequencies. Overall results suggest that in the ground state resonance structures of the benzenediazonium salts, the rehybridization of the C1—N1 bond is very unlikely and this bond remains as a single bond.