bluuebunny/crossref_metadata_2025 huggingface dataset:
Bicyclooctanone Rearrangement, [3.2.1] → [3.3.0], via β-Enolization. Evidence for γ-Enolization in Bicyclo[3.3.0]octan-2-one
Authors: Johnson A. L. , Petersen N. O. , Rampersad M. B. , Stothers J. B.
Published: May 2006

Under homoenolization (β-enolization) conditions (t-BuO−–t-BuOH, l85°) 3,3-dimethylbicyclo[3.2.1]octan-2-one rearranges to 3,3-dimethylbicyclo[3.3.0]octan-2-one in good yield. From reactions in t-butyl alcohol-O-d, the progress of deuterium incorporation was determined by 2H n.m.r. to compare the reactivity toward β-enolate formation for the various potential sites in 1. Similar experiments with 2 gave evidence for competitive γ proton abstraction (γ-enolization); the first example of this process in a relatively flexible carbon skeleton.
Radiation-Sensitized Thermal Cracking of n-Butane. II. Ionic Reactions
Authors: Matsuoka Shingo , Tamura Takaaki , Oshima Keichi , Oshima Yunosuke
Published: May 2006

Ionic reactions in the radiolysis of n-butane were studied at temperatures ranging from 17 to 548 °C. Ionic chain reactions were found for the first time to take part in the radiation-sensitized thermal cracking mechanism of hydrocarbon system.The isobutane and isobutene yields increased with increasing temperature and at 548 °C their G-values reached 31.2 and 12.1, respectively, though they were not formed by the thermal cracking of n-butane. The formation was completely suppressed by the addition of 0.15 mol% ammonia. They were produced with high yields irrespective of the kind of wall of the irradiation cells. It was concluded from these results that isobutane and isobutene were formed by homogeneous ionic chain reactions with activation energies. Part of the propane product was also found to have been formed by ionic chain reactions. From the effect of adding n-pentane on the yields of the ionic products, C4H9+ ion was inferred as the carrier ion.In the vicinity of room temperature, formation by ionic reactions of polymers with more than 14 carbon atoms was inferred from the material balance of the products from H2 to C14.
The Thermal Rearrangement of α-Substituted Silanes
Authors: Bassindale Alan R. , Brook A. G. , Jones Peter F. , Lennon John M.
Published: May 2006

The thermal rearrangement of α-substituted silanes (R3SiCHXR′), in which there is exchange of X and R between the silicon atom and the adjacent carbon atom, has been studied. Kinetic parameters for two compounds (Me3SiCBrPh2 and Ph3SiCHOAcPh) have been measured. Migratory aptitudes of both X and R have been examined. A mechanism involving initial migration of X to silicon, to form an "inverse ylid" [Formula: see text] is proposed.
The Reactivity of Tungsten Halides with Organic Sulfides: S-Dealkylation and Reductive Elimination Reactions
Authors: Boorman P. Michael , Chivers Tristram , Mahadev Kalabeerappa N.
Published: May 2006

Tungsten hexa- or pentachloride reacts with alkyl sulfides to give (R3S)2[WCl6]. The reactions involve S-dealkylation followed by reductive elimination of R2S2. Alkylation of R2S by RCl probably occurs at the tungsten site through the intermediacy of WCl4(R2S)2. The latter compounds have been shown to be unstable with respect to displacement of the sulfide ligands by halide ions or neutral donors and therefore form excellent intermediates for W(IV) synthetic chemistry.
Complexes of the Early Transition Metals with o-Mercaptophenol and 1,2-Dihydroxybenzene
Authors: Martin Joel L. , Takats Josef
Published: May 2006

A novel synthetic approach, based on the reactivity of amido derivatives of the transition metals, M(NR2)x, towards protic reagents, for the synthesis of complexes of Ti, Zr, Hf, Nb, and Ta with o-mercaptophenol and 1,2-dihydroxybenzene is reported. The complexes, isolated as their tetraalkylammonium and tetraphenylarsonium salts, are moderately air stable, well behaved 2:1 (Ti, Zr, Hf) and 1:1 (Nb, Ta) electrolytes. The u. v.–visible spectra of the complexes, which are somewhat reminiscent of the corresponding benzene-1,2-dithiolates, are dominated by ligand-to-metal charge transfer bands. The band positions change in the expected manner, hypsochromic shifts in the order C6H4S22− < C6H4SO2− < C6H4O22− for a given metal and Ti < Zr ∼ Hf, Nb < Ta, Nb < Zr for a given ligand. lt is argued that these spectral resemblances could be a possible indication of variations in coordination geometry of the reported complexes similar to the ones found in compounds of benzene-1,2-dithiol.
Preparation of the Piperazine– and Triethylenediamine–Monoborane Adducts of BH3, BH2F, BHF2, and BF3
Authors: Vanpaasschen J. M. , Geanangel R. A.
Published: May 2006

The new compounds, triethylenediamine–BH2F, –BHF2, –BF3 and piperazine–BH2F, –BHF2, –BF3 have been isolated and characterized from the base displacement reactions involving the diamine and the trimethylamine–fluoroboranes. By this method only the monoborane adducts of the difunctional amines are formed. The stability of these monoborane adducts is rationalized from a mechanistic point of view. The proton and boron-11 n.m.r. and i.r. spectra are presented with the analytical results.
The Thermal Decomposition of Alkoxycarbonyl Thiocyanates and Isothiocyanates
Authors: Liotta Dennis , Engel Robert
Published: May 2006

Alkoxycarbonyl thiocyanates and isothiocyanates have been decomposed thermally under reduced pressure at temperatures of 240–375°. Primary systems yield primarily alkyl thiocyanates, whereas secondary and tertiary systems yield alkyl isothiocyanates. The viability of using this reaction in a conversion of primary alcohols to primary alkyl thiols and secondary and tertiary alcohols to tertiary alkyl amines is discussed.
Dicarbonylcycloheptatrienylmolybdenum Derivatives of Silicon, Germanium, and Tin
Authors: Isaacs E. E. , Graham W. A. G.
Published: May 2006

Convenient procedures are reported for the synthesis of the compounds (η-C7H7)Mo(CO)2MR3 (M = Si, R = Cl; M = Ge, R = Cl, F, Ph; M = Sn, R = Cl, Ph ). The triphenyl derivatives were accessible through the anion [(η-C7H7)Mo(CO)2]−, while the MCl3 derivatives were prepared from (η-C7H7)Mo(CO)2Cl. Infrared, n.m.r., and mass spectrometric properties are reported.
Ion Pair Formation and Solvation Energies in Solutions of Alkali Halides in Dimethyl Sulfoxide. II. Model Calculations
Authors: Goldenberg Merrill S. , Kruus Peeter , Luk Stephen K. F.
Published: May 2006

Energy calculations were carried out on models of molecular-level structures likely to be present in solutions of alkali halides in dimethyl sulfoxide (DMSO). Classical electrostatic interactions were assumed, and polarization of a DMSO molecule was assumed due to the fields of the ions only. The validity of this assumption was tested. DMSO molecules were represented by increasingly detailed models, with most calculations carried out with each molecule represented by 10 point charges and 9 polarizable bonds. A program including up to 14 such molecules and two ions was used for energy and distance calculations, and is made available. Polarization effects are as important as interactions between permanent charges for energy calculations. The configurations of minimum energy determined by classical electrostatics often do not involve overlap of the "hard-sphere radii" of neighboring species, so that the neglect of quantum mechanical repulsive forces seems justified. Energy cycles using the calculated energies for ion–solvent complexes predicted experimental cation enthalpies with some success. The form of the potential for vibration of a cation in a solvent shell was investigated and found in cases not to have an energy minimum at the shell center. Calculations including next-nearest solvating DMSO's indicate a rather loose structure. An energy profile for an anion moving from a solvent-separated ion pair position to a contact-ion pair position is presented.
A Comparison of the Stereospecificity of Carbocation to Rearranged Carbocation Reactions under Observable Ion and Steady-state Intermediate Conditions
Authors: Haseltine Rollin P. , Sorensen Ted S.
Published: May 2006

From observable ion studies on a series of polymethyl tertiary 2-norbornyl cations, a huge difference in the migratory aptitudes (stereospecificity) of 3-exo and 3-endo methyl groups was observed. The same trend was observed under typical acid catalysis conditions where the same rearrangements are involved but where the cation is in this case a fleeting intermediate. In related work, a comparison was made of the absolute rate of an exo-3,2-hydride and an exo-3,2-methyl shift and a direct measurement of the H–D isotope effect in a 3,2-hydride shift was made.
Substituent Effects in Electron Transfer Reactions: The Preparation and Chromium(II) Reduction of 3-Formylpentane-2,4-dionatobis(ethylenediamine)cobalt(III). Preparation of the Linkage Isomer 2-Acetylbutane-1,3-dionatobis(ethylenediamine)cobalt(III)
Authors: Balahura Robert J. , Lewis N. A.
Published: May 2006

The preparation of the linkage isomers, 3-formylpentane-2,4-dionatobis(ethylenediamine)cobalt(III), (1), and 2-acetylbutane-1,3-dionatobis(ethylenediamine)cobalt(III), (2), are described. The kinetics of the reaction of Cr(OH2)62+ with 1 and the parent complex, 2,4-pentanedionatobis(ethylenediamine)cobalt(III), (3), have been studied spectrophotometrically in acidic solution. For 1, the reduction is described by the rate law −d ln [Co(III)complex]/dt = k[Cr2+], and k = 0.0863 M−1 s−1 at 25 °C, μ = 1.0 M (LiClO4). The activation parameters for this reaction were found to be ΔH≠ = 9.9 ± 0.5 kcal mol−1 and ΔS≠ = −30 ± 3 e.u. The reaction proceeded by an inner-sphere mechanism and the product of this reaction was isolated and characterized as 2-acetylbutane-1,3-dionatotetraaquochromium(III). The linkage isomer of this complex was also prepared. The parent complex (3) was not reduced by Cr(OH2)62+ at an observable rate and an upper limit for the rate constant of this reaction was assigned a value of 10−4–10−6M−1s−1 at 25 °C. The ability of the formyl group to enhance the rate of electron transfer is discussed, and the chromium(II) reduction studies of related chelated systems are compared with the results obtained in this investigation.
Microbiological Transformations of 17-Norkauran-16-one, ent-17-Norkauran-16-one, and 17-Norphyllocladan-16-one by Aspergillusniger
Authors: Anderson Allan B. , McCrindle Robert , Turnbull James K.
Published: May 2006

Incubation of 17-norkauran-16-one (3b) and ent-17-norkauran-16-one (2b) with Aspergillusniger gives the related C-3 equatorial alcohols 3c and 2c, respectively, whereas 17-norphyllocladan-16-one (4b) gives the 3β-alcohol 4c and the corresponding 3-ketone 4g. Yields of all of these products are low. Diketone 4g is identical with the corresponding compound derived from calliterpenone, thus confirming that calliterpenone should be formulated as 8 rather than 7.
The Temperature Dependence of the Ratio kd/kc for Ethyl Radicals
Authors: Hooper D. G. , Simon M. , Back M. H.
Published: May 2006

The ratio of the rate constants for disproportionation and combination for ethyl radicals, kd/kc[Formula: see text]has been measured over the temperature range 298–173 K in the gas phase. Ethyl radicals were produced by direct photolysis of ethylene followed by addition of hydrogen atoms to ethylene. At low temperatures the only important reactions of the radicals were combination and disproportionation. The ratio kd/kc was obtained from measurements of the rates of formation of ethane, butane, and butene. No change in the ratio kd/kc was observed over the temperature range studied, leading to the conclusion that Ed − Ec = 0, within the experimental error. The significance of this result is discussed in relation to other measurements in both gas and liquid phase and to the nature of the transition state for this reaction.
Secondary Deuterium Isotope Effects on Carbonyl Ylide Intermediates
Authors: Vukov Vesna , Crawford Robert J.
Published: May 2006

The formation of vinyldihydrofuran (6) and dihydrooxepine (5) is sensitive to deuterium substitution at the terminal methylene of 2,3-divinyloxirane. Intra- and intermolecular isotope effects have been examined and suggest that 5 is produced on a competitive basis with 6 from a common intermediate.
Crystal and Molecular Structure of B-Phenyl-diptychboroxazolidine,
Authors: Rettig Steven J. , Trotter James
Published: May 2006

Crystals of B-phenyl-dictychboroxazolidine are monoclinic, a = 8.4977(4), b = 9.0617(5), c = 7.0105(3) Å, β = 111.627(3)°, Z = 2, space group P21. The structure was solved by direct methods and was refined by full-matrix least squares procedures to a final R of 0.040 for 967 reflections with I ≥ 3σ(I). The bond lengths involving nonhydrogen atoms have been corrected for thermal motion. Bond lengths are: B—O, 1.460(3) and 1.474(3), B—N, 1.666(3), B—C, 1.613(3), C—O, 1.411(3) and 1.419(3), C—N, 1.485(3) and 1.486(3), C(sp3)—C(sp3), 1.514(4) and 1.524(4), C—C(ar), 1.384–1.400(4–6), mean C—H, 0.98(4), and N—H, 0.87(5) Å. The crystal structure consists of discrete molecules of B-phenyl-diptychboroxazolidine each linked to two others by N—H … O hydrogen bonds (O … N = 2.914(3) Å) to form continuous spirals along b.
2-Deacetylchelocardin: A Degradation Product of Chelocardin
Authors: Chu Daniel T. W. , Garmaise D. L. , Bernstein E.
Published: May 2006

A novel chemical transformation is described in which chelocardin 1, under normal ketalization conditions, is converted with elimination of the 2-acetyl group, to the bisdioxolane 2. Hydrolysis of 2 yields 2-deacetylchelocardin 4. The properties of the tricarbonylmethane system in 1 and of the 1,3-cyclohexanedione system in 4 are found to be profoundly modified by the presence of the 4-amino and the 12a-hydroxyl group.
Electron Spin Resonance Studies and Electronic Structure of trans-[Ti(H2O)4F2]+
Authors: Premović Pavle Ilija , West Paul Ronald
Published: May 2006

At pH 1.0–1.6 aqueous titanium(III) solutions containing added fluoride ion exhibit e.s.r. signals of trans-[Ti(H2O)4F2]+, g = 1.9460 ± 0.0005, aTi = 17.9 ± 0.2 G. The variation in the intensity of the optical and e.s.r. spectra with added fluoride ion indicate > 90% conversion to the complex at [Ti]:[F] = 1:2. The trans geometry of the complex is established from the spectrum in D2O, a 1:2:1 triplet with aF = 7.5 ± 0.5 G, and from the axial symmetry (D4h) apparent in the frozen solution spectrum, [Formula: see text]The optical spectrum shows two bands assigned to the 2B2g → 2B1g (15 200 cm−1) and 2B2g → 2A1g (23 300 cm−1) transitions. Calculations based on the e.s.r. and optical spectra suggest covalent character in the in-plane π and σ bonding of the complex.A des pH allant de 1.0 à 1.6, des solutions aqueuses de titane(III) contenant des ions fluorures ajoutés, montrent un signal r.p.e. du [Ti(H2O)4F2]+-trans, g = 1.9460 ± 0.0005, aTi = 17.9 ± 0.2 G. On note une variation de l'intensité des spectres optique et r.p.e. lorsqu'on ajoute des ions fluorures; cette variation indique que la conversion vers le complexe est plus grande que > 90% lorsque la concentration de [Ti]:[F] = 1:2. On a établi que le complexe possède la géométrie trans en se basant sur le spectre dans le D2O alors qu'on observe un triplet 1:2:1 avec aF = 7.5 ± 0.5 G et aussi sur l'existence d'une symétrie axiale (D4h) observée pour le spectre de la solution congelée [Formula: see text]
Reaction Sequences Involving the Mutual Interconversion of All 10 Tertiary Dimethyl-2-norbornyl Cations. A Comparison of Predicted Products and Rates with Experiment
Authors: Haseltine R. , Ranganayakulu K. , Wong N. , Sorensen T. S.
Published: May 2006

All 10 tertiary dimethyl-2-norbornyl cations have been prepared. There are sequences of individual steps which will in theory interconvert any given two of these cations, a total of 45 permutations. All of the possible sequences (within a defined limit on the allowable total number of steps) for performing these interconversions were determined using a digital computer. Each step used in the computer generated sequence had previously been assigned a trial activation free energy value and a comparison is made in this paper between the actual experimental rearrangement results (in terms of both the kinetics of disappearance for the cation and what product is in fact formed) and the predicted results.
Organoselenium Chemistry. Addition of Tolueneselenenyl Chloride to Ethylene: Concerning the Reported Isolation of a Stable Episelenurane
Authors: Reich Hans J. , Trend John E.
Published: May 2006

The addition of ethylene to solutions of 4-tolueneselenenyl chloride (ArSeCl) gives initially the selenide dichloride 5. Only after more than 20% of the theoretical amount of ethylene has been added does the normal adduct appear. This anomaly is caused by the reversible reaction of the normal adduct 4 with ArSeCl, giving diselenide and 5. The episelenurane 1 reported as a product of the reaction of ArSeCl with ethylene appears to be actually the dichloride 5. Even at low temperature no evidence for the formation of a stable episelenurane was obtained. The 13C n.m.r. spectra of several organoselenium compounds are reported, including a number of selenium-77 carbon-13 coupling constants.
A Facile Route to 1 → 6 Linked Disaccharides: Syntheses of 6-O-β-D-Glucopyranosyl-D-glucose (Gentiobiose) and of 2-Acetamido-6-O-(2-Acetamido-2-deoxy-β-D-galactopyranosyl)-2-deoxy-D-galactose
Authors: King Russell R. , Bishop Claude T.
Published: May 2006

The condensation of acetohalogeno sugars with unblocked benzyl hexopyranosides gave the 1 → 6 linked disaccharides exclusively and in good yield. The utility of this "open" synthesis was demonstrated by preparation of 6-O-β-D-glucopyranosyl-D-glucose (gentiobiose) and of a new disaccharide, 2-acetamido-6-O-(2-acetamido-2-deoxy-β-D-galactopyranosyl)-2-deoxy-D-galactose.
Conformations of Bridged Diphenyls. IX. Crystal Structure of 2-(4′-Carbomethoxy-2′-nitrothiophenyl)-1,3,5-trimethylbenzene
Authors: Van Der Heijden Simon P. N. , Chandler W. David , Robertson Beverly E.
Published: May 2006

The structure of 2-(4′-carbomethoxy-2′-nitrothiophenyl)-1,3,5-trimethylbenzene, C17H17-NO4S, has been determined by X-ray diffraction. The crystals are monoclinic, a = 18.616(15), b = 5.739(8), c = 15.712(14) Å, β = 101.97(3)°, P21/c with Z = 4. The intensities of 3820 independent reflections were measured on a four circle diffractometer; 2825 reflections were used in the refinement of the structure to give a final least-squares weighted residual of 0.059 and a traditional R factor of 0.054. The presence of electron-withdrawing groups on one of the phenyl rings increases the conjugation between the ring and the sulfur atom in a similar manner as that observed in diphenyl ethers. The mesityl ring is nearly orthogonal to the C—S—C plane.
On the Construction of Delphinine-type Alkaloids via the Rearrangement of Substituted Denudatine Derivatives
Authors: Wiesner Karel , Ho Pak-Tsun , Liu Wing-Cheong , Shanbhag Madhav N.
Published: May 2006

A simple and stereospecific conversion of compound 1 to the aconite alkaloid model 25 is described.
Base-catalyzed Degradations of Carbohydrates. VII. Alkaline Degradation of 3,6-Di-O-substituted Hexoses
Authors: Aspinall Gerald O. , Krishnamurthy Thinnayam N. , Furda Ivan , Khan Riaz
Published: May 2006

6-O-β-D-Glucopyranosyl-3-O-methyl-D-glucose (4) has been synthesized as a model com pound for regions of branching in polysaccharides. Alkaline degradation of the disaccharide affords an epimeric pair of O-glycosyl metasaccharinic acids which have been characterized by reduction to 3-deoxy-6-O-β-D-glucopyranosyl-D-ribo-hexose (6) and 3-deoxy-6-O-β-D-glucopyranosyl-D-arabino-hexose (7). Alkaline degradation of the branched β-D-glucan from Sclerotiumrolfsii followed by reduction of the derived metasaccharinic acids furnishes 3-deoxy-D-ribo-hexose (8), 3-deoxy-D-arabino-hexose (9), and the two disaccharides (6 and 7).
Base-catalyzed Degradations of Carbohydrates. X. Degradation by β-Elimination of Methylated Degraded Leiocarpan A
Authors: Aspinall Gerald O. , Chaudhari Atmaram S.
Published: May 2006

Treatment of methylated degraded leiocarpan A with l,5-diazabicyclo[5.4.0]undec-5-ene and acetic anhydride, followed by mild acid hydrolysis and de-O-acetylation, furnishes 3,4,6-tri-O-methyl-D-mannose and 3,4-di-O-methyl-6-O-(2,3,4-tri-O-methyl-β-D-xylopyranosyl)-D-mannose. The characterization of the methylated disaccharide provides evidence for the site of attachment and anomeric configuration of the D-xylopyranose end groups in the parent polysaccharide.
Base-catalyzed Exchange of Cyclic Diketones under Homoenolization Conditions; Facile Exchange at the Bridgehead and C-7 in 3,3,6,6-Tetramethyl Bicyclo[2.2.1]heptan-2,5-dione
Authors: Werstiuk Nick Henry
Published: May 2006

Treatment of 3,3,6,6-tetramethyl bicyclo[2.2.1]heptan-2,5-dione (1) under mild homoenolization conditions (t-BuO−, 175°, 28 h ) results in unusually facile exchange at the bridgehead and C-7. 1,4-Homoenolization to an endo methyl group, converts 1 into 2,2,5-trimethyl bicyclo[3.2.1]octan-3,8-dione(3).
The Microwave Spectrum, Dipole Moment, and Structure of Glycidol
Authors: Brooks W. V. F. , Sastry K. V. L. N.
Published: May 2006

The microwave spectra of glycidol [Formula: see text] and its deuterated (—OD) form have been studied in the range 8–40 GHz. The rotational (in MHz) and centrifugal distortion constants (in kHz) of glycidol are: A = 10 347.87, B = 4102.36, C = 3781.95; ΔJ = 2.38, ΔJK = −311, ΔK = 5.2, δJ = 0.3159, δK = −9.76. The rotational constants and distortion constants of glycidol (OD) are A = 10 010.31, B = 4056.73, C = 3717.02; ΔJ = 2.53, ΔJK = 197, ΔK = 7.7,δJ = 0.3532,δK = −7.19. The dipole moment components of the normal molecule in Debye units are μa = 0.61, μb = 1.20, μc = 0.52, and the total dipole moment is 1.44 D.A structure is derived with the alcoholic hydrogen atom close (2.5 Å) to the ring oxygen. The structure and the absence of signs of free or hindered rotation, can be accounted for by hydrogen bonding between the proton and the ring oxygen.
The Photolysis of Matrix Isolated cis-Thionylimide. 2. The Identification and Infrared Spectra of trans-HNSO and NSO
Authors: Tchir Peter O. , Spratley Richard D.
Published: May 2006

It is shown that the low energy (λ > 3000 Å) photolysis of cis-HNSO in an argon matrix leads to formation of trans-HNSO. Four i.r. absorptions are observed and assigned for trans-HNSO and an approximate partial force field is calculated using data from isotopic substitutions. A comparison is made of the i.r. spectra of cis- and trans-HNSO using the intramolecular hydrogen bond of the cis form as a basis for explanation of the differences. Photolysis of cis-HNSO in argon matrices using vacuum u.v. light (1216 Å) has resulted in a single i.r. absorption at 1195 cm−1 which has been assigned to the radical, NSO.
The Role of Cobalt in Unsupported MoS2 Hydrodesulfurization Catalysts
Authors: Furimsky E. , Amberg C. H.
Published: May 2006

Crystalline MoS2 catalysts were impregnated with cobalt over the total composition range, and their catalytic activity in the hydrodesulfurization of thiophene tested in a microreactor at 400° and near atmospheric pressure. Three principal composition regions could be distinguished in the sulfided catalysts: (1) Co/(Co + Mo) compositions 0–0.4. In this region intercalated Co enhances the intrinsic activity which reaches a maximum near a Co content of 0.25. The region is sulfur "deficient" with respect to MoS2 + Co9S8 and there is no evidence for the presence of Co9S8. (2) Compositions 0.4–0.65. This region is characterized by the exact stoichiometry MoS2 + Co9S8 and by the appearance of a Co9S8 phase. Surface area experiences a fivefold increase, as does percent conversion, but intrinsic activity changes very little. (3) Compositions > 0.65. A region of lesser interest, it is sulfur "deficient", possibly through the formation of Co4S3, and surface area decreases steeply with Co content.
New Access to Noradamantanes via Generation of Selectively Protected Bicyclic β-Diketones
Authors: Gravel D. , Rahal S.
Published: May 2006

The synthesis of 2,9-disubstituted and 2- and 9-monosubstituted noradamantanes is described starting from 4-acetoxycyclohexanone. The key step in this approach is the generation of selectively protected 7-acetoxybicyclo[3.3.1]nonane-2,9-dione by trapping the imminium salt precursor by an acetalyzing reagent.
The Catalytic Decomposition of 2-Propanol on Magnesium Oxide
Authors: Hoodless Ian M. , Martin G. Douglas
Published: May 2006

The catalytic decomposition of 2-propanol on powders of "pure" and lithium oxide doped magnesium oxide has been investigated in the temperature range 300–450 °C by a pulse reactor technique. With the "pure" magnesium oxide samples the selectivity for dehydrogenation decreases with increasing temperature with an abrupt change in the region of 375 °C. The effect of the lithium oxide dopant is to depress the selectivity for dehydrogenation at the lower temperatures. The dopant does not appear to affect the dehydration activity and the decrease in selectivity is ascribed to the strong chemisorption of acetone at anion vacancies.
Bicyclooctanone Rearrangement, [3.2.1] → [3.3.0], via β-Enolization. Evidence for γ-Enolization in Bicyclo[3.3.0]octan-2-one
Authors: Johnson A. L. , Petersen N. O. , Rampersad M. B. , Stothers J. B.
Published: May 2006

not available
The Equilibrium Constant for the Formation of Al2(OH)24+ in Aqueous Solutions
Authors: Turner R. C.
Published: May 2006

The equilibrium constant for the formation of the aluminum hydroxy dimer, Al2(OH)24+, was calculated from measured values of pH and the concentrations of the dimer and trivalent aluminum in aqueous solutions at 25 °C. The concentrations of Al2(OH)24+ was determined by a method based on its rate of reaction with an 8-hydroxyquinoline – sodium acetate solution. Experiments were made with various concentrations of aluminum and different ionic strengths. With an ionic strength of 0.06, the equilibrium constant was 10−7.42 and increased with decreasing ionic strength. The negative log of the equilibrium constant when the ionic strength approaches zero was estimated to be 6.95 ± 0.05.
Reductive Cleavage of Acetals and Ketals by Borane. Part II. The Kinetics of the Reaction
Authors: Bolker Henry I. , Fleming Bruce I.
Published: May 2006

The reductive cleavage of acetals with borane in tetrahydrofuran was found to be first order in acetal and close to third order in borane. The high order in borane may be due to the participation of three BH3 units in the transition state with subsequent formation of a B2H7− ion. All the hydrogen atoms of borane are available for the reduction of excess acetal at 30 °C.
Studies Related to Antitumor Antibiotics. Part VI. Correlation of Covalent Cross-linking of DNA by Bifunctional Aziridinoquinones with their Antineoplastic Activity
Authors: Akhtar M. Humayoun , Begleiter Asher , Johnson Douglas , Lown J. William , McLaughlin Larry , Sim Soo-Khoon
Published: May 2006

Certain bisaziridinopyrrolidinoquinone analogs, which contain the structural moieties essential for physiological activity in the parent antitumor agent mitomycin C, have been synthesized. These compounds efficiently induce covalent cross-links in DNA as shown by the ethidium fluorescence assay which was confirmed by an independent S1-endonuclease assay. The interaction of clinically active and structurally related antitumor aziridinoquinones with DNA have been examined similarly. The aziridinoquinones cross-link DNA efficiently with a marked pH dependence. Parallel dependence is observed on pH and concentration of alkylating species in the concomitant alkylation which does not result in cross-linking as measured by the suppression of the before heat fluorescence. The latter phenomenon was shown by the application of radiolabelled polynucleates not to be accompanied by depurination. A direct correlation exists between the extent of covalent cross-linking and (G + C) content of various DNA's of comparable molecular weight as in the case of mitomycin C. Estimates of the average number of cross-links per DNA molecule range from 0.61 to 1.71 depending on (G + C) content. The rate of acid assisted opening of a model aziridinoquinone measured spectrophotometrically at different pH values parallels the observed rate of covalent cross-linking and alkylation. It was shown independently that the intermediate 2,5 bis(2-acetoxyethyl-amino)-3,6-dimethoxy-1,4-benzoquinone does not cross-link DNA. A correlation is made of antineoplastic activity against a variety of tumors with covalent crosslinking ability using λ-DNA.
Photoreaction of Nitroso Compounds in Solution. Part XXXII: Synthesis and Reaction of 2-Nitrato-3-Aminonorbornanes
Authors: Pillay K. Somosekharen , Hanaya Kaoru , Chow Yuan L.
Published: May 2006

Oxidative photoaddition of nitrosamines to norbornene gave both cis-exo- and trans-2-nitrato-3-aminonorbornanes that were stable in their protonated form under photolysis conditions. The free bases underwent a novel cleavage reaction assisted by the lone pair of the amino group to give l,3-bis(formyl)cyclopentane. In addition these nitrates also underwent solvolysis to give cis-exo-2-hydroxy-3-aminonorbornane. The mechanisms of these basic decompositions are discussed.
The Mechanism of Hydrolysis of Imidate Salts. The Importance of Stereoelectronic Control and pH of the Reaction Medium on the Cleavage of Tetrahedral Intermediates
Authors: Deslongchamps Pierre , Taillefer Roland J.
Published: May 2006

Hydrolysis of anti imidate salts give the ester amine products exclusively over the entire range of pH. Hydrolysis of syn imidate salts in acidic and neutral conditions give the ester amine products only; in basic conditions, mixtures of ester amine and amide alcohol products are observed. These results are explained by the application of the new theory of stereoelectronic control on the various ionic forms T+, T±, and T− of the tetrahedral intermediate. For syn imidate salts, conformational changes of the tetrahedral intermediate must occur in order to have cleavage with stereoelectronic control.
Esters Chromiques Dérivés D'alcools Tertiaires
Authors: Richer Jean-Claude , Hachey Jean-Marie
Published: May 2006

Chromic acid esters derived from tertiary alcohols have been synthesized and characterized via infrared, ultraviolet, and proton magnetic resonance spectroscopy.
Réactivité de la combinaison anthracène–lithium vis-à-vis des nitriles
Authors: Mazaleyrat Jean-Paul
Published: May 2006

Lithium anthracenylide in ethereal solution behaves as a basic reagent towards nitriles with acidic hydrogens. However, in the case of nitriles with a tertiary α-carbon atom, two competitive reactions may occur: nucleophilic attack and electron transfer. The nucleophilic addition is faster, but because of its reversibility, the reaction proceeds, through the electron transfer process which is followed by the irreversible breaking of the C—CN bond, towards the formation of 9-alkyl-9,10-dihydroanthracene.
5-Allyl-9-oxobenzomorphans. Part 2. The Crystal and Molecular Structure of an Unusual Product of Dequaternization of 5-Allyl-9-oxobenzomorphan Methobromide
Authors: Ahmed Farid R. , Saucier Michel , Monković Ivo
Published: May 2006

The synthesis of 5-allyl-2'-methoxy-9-oxo-6,7-benzomorphan (5b) is described. The 10-hydroxy-2-methyl-1,11-propano-9H-indeno-1,2,10,11-tetrahydro[2,1-c]pyridine (7a) and the corresponding 6-methoxy derivative (7b) are unexpected products of pyrolysis of 5-allyl-2-methyl-9-oxobenzomorphan methobromide (4a) and 5-allyl-2′-methoxy-2-methyl-9-oxobenzomorphan methobromide (4b) respectively. The molecular structure of 7a (C16H19NO) has been determined from spectral and microanalytical data, and confirmed by X-ray single crystal analysis on its hydrobromide salt using the heavy atom technique. The crystals of [C16H20NO]+Br− are monoclinic, P21/a, with a = 13.724(2), b = 14.022(3), c = 7.495(2) Å, β = 97.33(5)°, and Z = 4. The crystal structure has been refined by block-diagonal least-squares calculations to R and Rw = 0.036 for the 2197 observed reflections. The N atom has planar trigonal coordination, and forms one double and two single C—N bonds of lengths 1.273(4), 1.465(4), and 1.474(4) Å, respectively. The Br is hydrogen-bonded to O. The N and O atoms are trans.
Group VI Metal Carbonyl Derivatives of cis-(CH3)2AsC(CF3)=C(CF3)As(CH3)2
Authors: Cullen William R. , Mihichuk Lynn
Published: May 2006

The carbonyls M(CO)6 (M=Cr, Mo, W) react with cis-(CH3)2AsC(CF3)=C(CF3)As(CH3)2 (L—L) to give the chelate derivatives (L—L)M(CO)4. These react with excess (L—L) on ultraviolet irradiation affording cis-(L—L)2M(CO)2 and trans-(L—L)2M(CO)2 and two isomers of fac-(L—L)2M(CO)3 where one (L—L) is acting as a monodentate ligand, and is either the cis ligand or its trans isomer.
The Raman Spectra of some Tricoordinate Halogenocadmate(II) Anions in the Solid State
Authors: Contreras J. Guillermo , Tuck Dennis G.
Published: May 2006

The Raman spectra of the solids n-Pr4N[CdX3], where X is Cl, Br, or I, show that trihalogenocadmate anions possess C2v symmetry in the solid state. Force constants have been calculated using the Urey–Bradley approximation and are correlated with the values reported for other tricoordinate species.
Coordination Compounds of Indium. Part XXX. Pyrrole Complexes of Indium(III) and Dimethylindium(III)
Authors: Chung Henry L. , Tuck Dennis G.
Published: May 2006

Preparative and spectroscopic studies show that the interaction of 2-formylpyrrole, C4H4N. CHO, and 2-acetylpyrrole, C4H4N·COCH3 (= HL), with In(III) may involve the organic base as either a bidentate organic anion ligand to give InL3 complexes, (L = 2-acetylpyrrolate only) or as a neutral monodentate species to form InCl3·3HL. The spectroscopic and kinetic properties of the organometallic derivatives Me2InL are also discussed. The polarographic reduction of InL3 (L = 2-acetylpyrrole anion) involves three one-electron reduction steps.
Virtual Bond Method in Conformational Analysis of Polymers
Authors: Sundararajan Pudupadi R. , Marchessault. Robert H.
Published: May 2006

A detailed description of the virtual bond method is presented. Simple equations are set up to examine the various relative dispositions of the repeating units along the polymer helix, if the repeat distance and the screw symmetry are known from X-ray data. The method is demonstrated with the examples of β-D-1,4′-xylan helix and the α-helix. Due to the rapidity and simplicity of this procedure, the effect of using different geometries for the residues can be examined readily. Diagrams are presented, from which one can deduce the torsion angles[Formula: see text], ψ for the various values of the valence angle at the bridge atom. This method does not involve a prior knowledge of [Formula: see text] ψ and hence, derivation of atomic coordinates of the residue for Fourier transform or structure factor calculations is simple.
Crystal Structure of Zn3V0.5P1.5O8
Authors: Idler K. Loralee , Calvo Crispin
Published: May 2006

The stable phase in the Zn3(PO4)2–Zn3(VO4)2 system near 25 mol% Zn3(VO4)2 is monoclinic with space group C2/c and unit cell parameters a = 15.941(6), b = 5.314(2), c = 8.265(2) Å, β = 106.96(3)° and Z = 4. The structure was refined by full-matrix least-squares methods using 910 reflections, R = 0.073. The composition, Zn3P1.50V0.50(4)O8, was determined by site population analysis with the V and P randomly distributed. One-third of the zinc ions lie on twofold axes and these show an average Zn—O bond length of 1.955 Å while the remaining ZnO4 group has a mean Zn—O bond length of 1.948 Å. The structure consists of sheets parallel to (100) formed of chains containing rings of corner shared Zn(1)O4 and (V,P)O4 tetrahedra. The Zn(2)O4 groups, in turn, form chains parallel to the b axis through corner sharing.
JNK and PI3K differentially regulate MMP-2 and MT1-MMP mRNA and protein in response to actin cytoskeleton reorganization in endothelial cells
Authors: Ispanovic Eric , Haas Tara L.
Published: May 2006

Increased production and activation of matrix metalloproteinase-2 (MMP-2) are critical events in skeletal muscle angiogenesis and are known to occur in response to mechanical stresses. We hypothesized that reorganization of the actin cytoskeleton would increase endothelial cell production and activation of MMP-2 and that this increase would require a MAPK-dependent signaling pathway in endothelial cells. The pharmacological actin depolymerization agent cytochalasin D increased expression of MMP-2 and membrane type 1-matrix metalloproteinase (MT1-MMP) mRNA, and this was reduced significantly in the presence of the JNK inhibitor SP600125. Activation of JNK by anisomycin was sufficient to induce expression of both MMP-2 and MT1-MMP mRNA in quiescent cells. Downregulation of c-Jun, a downstream target of JNK, with small interference (si)RNA inhibited MMP-2 expression in response to anisomycin. Inhibition of phosphoinositide 3-kinase (PI3K), but not JNK, significantly decreased the amount of active MMP-2 following cytochalasin D stimulation with a concurrent decrease in MT1-MMP protein. Physiological reorganization of actin occurs during VEGF stimulation. VEGF-induced MMP-2 protein production and activation, as well as MT1-MMP protein production, depended on PI3K activity. VEGF-induced MMP-2 mRNA expression was reduced by inhibition of JNK or by treatment with c-Jun siRNA. In summary, our results provide novel insight into the signaling cascades initiated in the early stages of angiogenesis through the reorganization of the actin cytoskeleton and demonstrate a critical role for JNK in regulating MMP-2 and MT1-MMP mRNA expression, whereas PI3K regulates protein levels of both MMP-2 and MT1-MMP.
Mathematical Models of Proprioceptors. II. Structure and Function of the Golgi Tendon Organ
Authors: Mileusnic Milana P. , Loeb Gerald E.
Published: May 2006

We developed a physiologically realistic mathematical model of the Golgi tendon organ (GTO) whose elements correspond to anatomical features of the biological receptor. The mechanical interactions of these elements enable it to capture all salient aspects of GTO afferent behavior reported in the literature. The model accurately describes the GTO's static and dynamic responses to activation of single motor units whose muscle fibers insert into the GTO, including the different static and dynamic sensitivities that exist for different types of muscle fibers (S, FR, and FF). Furthermore, it captures the phenomena of self- and cross-adaptation wherein the GTO dynamic response during motor unit activation is reduced by prior activation of the same or a different motor unit, respectively. The model demonstrates various degrees of nonlinear summation of GTO responses resulting from simultaneous activation of multiple motor units. Similarly to the biological GTO, the model suggests that the activation of every additional motor unit to already active motor units that influence the receptor will have a progressively weaker incremental effect on the GTO afferent activity. Finally, the proportional relationship between the cross-adaptation and summation recorded for various pairs of motor units was captured by the model, but only by incorporating a particular type of occlusion between multiple transduction regions that were previously suggested. This occlusion mechanism is consistent with the anatomy of the afferent innervation and its arrangement with respect to the collagen strands inserting into the GTO.
In vitro and In vivo Radiosensitization Induced by the Ribonucleotide Reductase Inhibitor Triapine (3-Aminopyridine-2-Carboxaldehyde-Thiosemicarbazone)
Authors: Barker Christopher A. , Burgan William E. , Carter Donna J. , Cerna David , Gius David , Hollingshead Melinda G. , Camphausen Kevin , Tofilon Philip J.
Published: May 2006

Purpose: Because ribonucleotide reductase (RR) plays a role in DNA repair, it may serve as a molecular target for radiosensitization. Unlike previously investigated RR inhibitors, Triapine potently inhibits both RR holoenzymes. Therefore, the effects of Triapine on tumor cell radiosensitivity were investigated.

Experimental Design: The effects of Triapine on the in vitro radiosensitivity of three human tumor cell lines and one normal cell line were evaluated using a clonogenic assay. Growth delay was used to evaluate the effects of Triapine on in vivo tumor radiosensitivity. The levels of the RR subunits were determined using immunoblot analysis and DNA damage and repair were evaluated using γH2AX foci.

Results: Exposure of the tumor cell lines to Triapine before or immediately after irradiation resulted in an increase in radiosensitivity. In contrast, Triapine enhanced the radiosensitivity of the normal fibroblast cell line only when the exposure was before irradiation. There were no consistent differences between cell lines with respect to the expression of the RR subunits. Whereas Triapine had no effect on radiation-induced γH2AX foci at 1 hour, the number of γH2AX foci per cell was significantly greater in the Triapine-treated cells at 24 hours after irradiation, suggesting the presence of unrepaired DNA damage. Triapine administration to mice bearing tumor xenografts immediately after irradiation resulted in a greater than additive increase in radiation-induced tumor growth delay.

Conclusions: These results indicate that Triapine can enhance tumor cell radiosensitivity in vitro and in vivo and suggest that this effect involves an inhibition of DNA repair.
Stoic Gunk
Authors: Nolan Daniel
Published: May 2006

The surviving sources on the Stoic theory of division reveal that the Stoics, particularly Chrysippus, believed that bodies, places and times were such that all of their parts themselves had proper parts. That is, bodies, places and times were composed of gunk. This realisation helps solve some long-standing puzzles about the Stoic theory of mixture and the Stoic attitude to the present.
Characteristic Features of Islamic Law: Perceptions and Misconceptions
Authors: Zahraa
Published: May 2006

No Abstract
The Legal Environment for Investment in Egypt in the New Millennium
Authors: Riad
Published: May 2006

No Abstract
Constitutional and Statutory Provisions Regarding the Appointment and Removal of Judges in the United Arab Emirates
Authors: Taneja
Published: May 2006

No Abstract
The US Egyptian Free Trade Agreement – Challenges and Prospects
Authors: Zohny
Published: May 2006

No Abstract
L'Obligation de Non-concurrence en Contrat de Travail: Etude Comparative en Droits Français et Koweitien
Authors: Al-Kandari
Published: May 2006

No Abstract
Arab Islamic Developments on Human Rights
Authors: Koraytem
Published: May 2006

No Abstract
UAE Ministerial Decree No. 612 of 2000
Authors: Translated by Al Tamimi & Company
Published: May 2006

No Abstract
Arbitration Practice in the UAE
Authors:   Dimitrakopoulos
Published: May 2006

No Abstract
Vicarious Liability: A Study of the Liability of the Guardian and his Ward in the Islamic Law of Tort
Authors:   Basir bin Mohamad
Published: May 2006

No Abstract
Gumilev and Huntington: Approaches and Terminologies
Authors: Goudakov Vladimir
Published: May 2006

In the 1990s I began to prepare a thesis on ‘Inter-ethnic relations in the Northwest Caucasus from the 13th to the 19th centuries’. From the outset of this project, I ran up against two difficulties: which approach to follow and which terminology to use.
Le passage des frontières: Impulses, Overtures…(A Postscript)
Authors: Dressler Wanda
Published: May 2006

This issue asks questions about the future of today's borders in a period of globalization and the end of bipolarization. In this new situation we are witnessing the unprecedented formation of huge regional and subregional groupings on an intercontinental scale. This allows us to glimpse the sketch plan for building a multipolar world, to compete with a world dominated by American power, against which continents and subcontinents are starting to unite to reformulate new rules of exchange. They present themselves as surprise competitors for the human masses they represent, Central and South America, India, Asia, Africa …. The borders that traditionally separated states according to dividing lines that were stable and clearly identifiable have suddenly started to become porous and act in accordance with a new and complex logic we need to redefine.
Calculation of the relative bonded area and scattering coefficient from sheet density and fibre shape
Authors: Batchelor Warren J. , Kibblewhite R. Paul
Published: May 2006

The fraction of the available fibre surface in a sheet that is bonded to other fibres is the relative bonded area (RBA), which is an important determinant of sheet mechanical properties. The main method for estimating RBA has been to extrapolate data for the light scattering coefficient as a function of tensile strength to zero tensile strength. This method can produce significant errors. In this paper, the light scattering coefficient, corrected for the total surface area of the fibres available for scattering, was plotted against sheet density, corrected for fibre shape. This was carried out for sheets made from several series of pulps, including single furnishes of long- and short-fibre bleached and unbleached pulps, as well as sheets made of blends of bleached long- and short-fibre pulps. The corrected scattering coefficient was inversely linearly correlated to the corrected density for each data set. A theory was developed to allow RBA calculation from the intercept and slope of the fitted line.
Epidemiology of Nonfatal Deliberate Self‐Harm in the United States as Described in Three Medical Databases
Authors: Claassen Cynthia A. , Trivedi Madhukar H. , Shimizu Iris , Stewart Sunita , Larkin Gregory Luke , Litovitz Toby
Published: May 2006

The absence of validated U.S. rates of nonfatal suicidal behavior places risk management and injury prevention programs at danger of being poorly informed and inadequately conceptualized. In this study we compare estimated rates of intentional self‐harm from two ongoing surveys (National Electronic Injury Surveillance System‐All Injury Program‐NEISS‐AIP; National Hospital Ambulatory Medical Care Survey‐NHAMCS) to data from the Toxic Exposure Surveillance System. Results suggest that, for every 2002–2003 suicide, there were 12 (NEISS‐AIP) or 15 (NHAMCS) self‐harm–related emergency department visits, and for every intentional self‐poisoning death there were 33 intentional overdoses reported to poison control centers, of which two ultimately went untreated.
Stressful Segregation Housing and Psychosocial Vulnerability in Prison Suicide Ideators
Authors: Bonner Ronald L.
Published: May 2006

Psychosocially vulnerable prisoners under stressful conditions of confinement are ill prepared to cope and at risk for developing suicide intention. The present study examined the relationships of depression, hopelessness, reasons for living, mental health problem history, suicide attempt lethality history, and stressful segregation housing with suicide ideation in 134 prisoners. Prisoners housed in segregation were found to have significantly higher levels of depression and suicide ideation than prisoners in general population. A hierarchical regression model of suicide ideation found significant interactions between mental health problem history, suicide attempt lethality history, and hopelessness with anticipated segregation stress, independent of depressed mood. Results of the study are discussed in terms of the stress‐vulnerability model, various methodological limitations, and future research.