bluuebunny/crossref_metadata_2025 huggingface dataset:
Intramolecular alkylation of a ketone by 1,2-epoxide groups of differing stereochemistry
Authors: Warnhoff E. W. , Srinivasan V.
Published: May 2006

The intramolecular alkylation of a ketone by three epoxide stereoisomers of 1 has been studied. Although a variety of products are possible a priori, in tert-BuOH–H2O–KOH each reaction yields a preponderant product. The course of these reactions can be rationalized by considering the accessibility of both faces of the three possible enolates to the backside of each carbon of the epoxide group for the SN2 reaction.
Vapour pressures of aqueous solutions of AgNO3 + TlNO3 by the static method at 98.5 °C
Authors: Trudelle Marie-Christine , Abraham Maurice , Sangster James
Published: May 2006

Vapour pressures of the system (Ag,Tl)NO3 + H2O have been measured at 98.5 °C by the static method over the complete concentration range for Ag/Tl mole ratio = 1.14. The water activity data can be represented by a modified BET isotherm in the range 0.1 < aw < 0.7. The derived BET constants indicate that the salts in this system are very weakly hydrated, probably less so than (for example) CsNO3. The linearity of vapour pressure with water mole ratio RH, found previously by Tripp and Braunstein for (Li,K)NO3 + H2O, is absent in the present system. The Henry's law constant for water dissolved in molten (Ag,Tl)NO3 has been deduced. The excess free energy of the system is positive at all concentrations and shows a maximum of 117 cal/mol at water mole fraction 0.66.
The sodium borohydride reduction of N-sulfonylpyridinium salts. Synthesis of N-sulfonyl-1,4-(1,2-) dihydropyridines
Authors: Knaus Edward E. , Redda Kinfe
Published: May 2006

Reaction of alkyl (aryl) sulfonyl chlorides and sulfonic acid anhydrides with pyridine in the presence of sodium borohydride afford N-sulfonyl-1,4-dihydropyridines (1) and N-sulfonyl-1,2-dihydropyridines (2). The ratio of products (1:2) was dependent upon solvent and temperature. Reaction of 2d with 4-phenyl-1,2,4-triazoline-3,5-dione (4) afforded the endo-adduct 5.
Multilayer oxidation of polycrystalline platinum
Authors: Berry Robert J.
Published: May 2006

The formation of a visible oxide film on polycrystalline Pt foil and wire is reported, and positively identified. The conditions for growth and dissociation of the oxide are outlined, and the energy of decomposition is estimated.
Structural determinations of liquid semiconductors using extended X-ray absorption fine structure
Authors: Crozier E. D. , Lytle F. W. , Sayers D. E. , Stern E. A.
Published: May 2006

The extended fine structure in the X-ray absorption coefficient is dominated by the interference of the photoelectron scattered by atoms in the immediate neighbourhood of the atom which absorbs the X-ray photon and thus can provide structural information about ordered or disordered systems. In this paper it is demonstrated that Extended X-Ray Absorption Fine Structure (EXAFS) measurements can be made on liquid systems at high temperatures. The technique is illustrated with results for As2Se3 in the liquid and amorphous states for temperatures between 100 and 773 K. A Fourier analysis of the EXAFS data reveals that a major structural rearrangement does not occur in the nearest neighbour shell when As2Se3 is melted. However, small structural changes do occur at the melting point which, within the limitations of the present data, suggest a slight increase in the nearest neighbour As–Se distance, a decrease in the number of nearest neighbours, and a decrease in the nearest neighbour disorder term σ12.
Correlation of optical and electron spin resonance spectra for metal–electron species in alkali metal solutions
Authors: Seddon William Arthur , Fletcher John Wallace , Catterall Ron
Published: May 2006

Pulse radiolysis of alkali metal cations (M+) in amines and tetrahydrofuran has demonstrated the formation of transient optical absorption bands attributed to a species of stoichiometry M. Such bands exhibit a distinct blue shift from that of es− observed in the same solvent. Comparisons with electron spin resonance (esr) spectra obtained in alkali metal solutions demonstrate that the blue shift can be correlated with the percent atomic character deduced for the species of the same stoichiometry. This correlation indicates that both the optical and esr spectra arise from the same species which, with decreasing solvent polarity, exhibits a continuous transition from well solvated ion-pairs to something approaching solvated atoms or tight ion-pairs.
The photoinsertion of tin(II) chloride into the metal–metal bond of hexacarbonylbis(tri-n-butylphosphine)dicobalt
Authors: Barrett Peter F. , Fox Arnold , March Raymond E.
Published: May 2006

The photochemical insertion reaction of SnCl2 into the metal–metal bond of [P(n-C4H9)3Co(CO)3]2 has been studied in THF at 23.0 °C at the irradiating wavelengths 365 nm, 436 nm, and 546 nm. At 365 nm, the quantum yield for the reaction increases with increasing concentration of SnCl2 and approaches a limiting value of 1.0. At 436 nm, however, the quantum yield increases above 1.0 and at 546 nm, quantum yields as high as 6 were measured. The uv–visible absorption spectrum of [P(n-C4H9)3Co(CO)3]2 shows an intense band at 372 nm and a broad shoulder at about 440 nm. A simple mechanism is proposed to operate on irradiation at 365 nm due to absorption by the intense band, but a more complicated chain mechanism is suggested to operate at 546 nm as a result of absorption by the lower energy shoulder band. It appears that both mechanisms operate on irradiation at 436 nm due to the overlap of the two absorption bands at this wavelength.
Comments on "Librations around the C(S)–phenyl bond in N-thiobenzoylmorpholines observed by 220 MHz proton magnetic resonance spectroscopy"
Authors: Berg Ulf
Published: May 2006

The interpretation of the temperature dependent nmr spectra of the three thiobenzmorpholides 1–3 in terms of torsional libration proposed in the title article is criticized. Pure samples of cis-1 and trans-1 have been prepared and studied by dynamic 1H and 13C nmr. A new interpretation is presented which involves the freezing of the passage over the steric barrier with a planar Ph—C(S)N transition state.
5-Allyl-9-oxobenzomorphans. Part 4. Synthesis of 3-hydroxy-8-oxyisomorphinans, 5-allyl-9α-hydroxy-6,7-benzomorphans, and related tetrahydrofuranobenzomorphans
Authors: Lambert Yvon , Daris Jean-Paul , Monković Ivo
Published: May 2006

A series of 3-hydroxy-8-oxyisomorphinans (11, 16) has been synthesized from the corresponding 5-allyl-9β-hydroxy-6,7-benzomorphans (7, 12) via a hydroboration, oxidation, mesylation, and cyclization sequence of reactions. Selective reduction of and methylmagnesium iodide addition to 5-allyl-2′-methoxy-2-methyl-9-oxo-6,7-benzomorphan (1) gave the respective 9α-hydroxy-6,7-benzomorphans (17). These were transformed to a number of 2-substituted-5-allyl-2′,9β-dihydroxy-6,7-benzomorphans (22) and corresponding methyltetrahydrofurano analogs (24).
Crystal and molecular structure of 2,2,4,6,6-pentamethyl-5-benzoyl-4-(N-methylbenzamido)-1,3-diaza-2,4,6(Pv)-triphosphorin
Authors: Oakley Richard T. , Paddock Norman L. , Rettig Steven J. , Trotter James
Published: May 2006

Crystals of 2,2,4,6,6-pentamethyl-5-benzoyl-4-(N-methylbenzamido)-1,3-diaza-2,4,6(Pv)-tri-phosphorin are triclinic, a = 13.375(1), b = 11.313(1), c = 7.925(1) Å, α = 107.72(1), β = 98.23(1), γ = 87.00(1)°, Z = 2, space group [Formula: see text]. The structure was solved by Patterson and Fourier syntheses and was refined by full-matrix least-squares procedures to a final R of 0.067 and Rw of 0.089 for 3954 reflections with. I ≥ 3σ(I) The P3N2C ring is nearly planar and has a conformation corresponding to a flattened version of the chair – twist boat. Bond lengths in the azaphosphorin ring, P—N, 1.579–1.614(2), and P—C, 1.752(3) and 1.777(3) Å, indicate conjugation with the C-benzoyl group. The exocyclic P—N bond length, 1.742(3) Å, is longer than those in related compounds as a result of competitive electron withdrawal from the N-benzoyl group. Other bond lengths (corrected for libration) are: mean P—Me, 1.796(4); C=O, 1.242(3) and 1.247(4); C—N, 1.472(3) and 1.369(4); mean C—C(phenyl), 1.391(10); other C(sp2)—C(sp2); 1.417–1.518(4) Å.
Juvabione and its analogues.: IV. Isolation, identification, and occurrence of juvabione, juvabiol, and epijuvabiol from the whole wood of Abies lasiocarpa
Authors: Manville John F. , Kriz Charalyn D.
Published: May 2006

Juvabione (1), 1′Z-dehydrojuvabione (10a), 1′E-dehydrojuvabione (10b), juvabiol (3), epijuvabiol (6), and the epimeric 2′-dehydrojuvabi-1′-ols (11) occur in the whole wood of a number of North American Abieslasiocarpa trees. Wide variability of occurrence of these juvabione analogues and other previously characterized extractives is noted. The co-occurrence of 1 and 6, with opposite configurations at C-1′, as shown by 13C nmr indicates the necessity of accurately determining the complete structure of naturally occurring compounds even if isolated from the same source.
Complex formation between sulfur dioxide and halide ions
Authors: Milanova Etela , Benoit Robert L.
Published: May 2006

Complex formation between sulfur dioxide and iodide ions in acetonitrile (AN) has been studied by vapour pressure measurements. The enthalpy changes ΔH0 for 1:1 association reactions between SO2 and halide (X−) ions in AN and between SO2 and Cl− in dimethylsulfoxide (DMSO) have been determined at 25 °C by calorimetry. The ΔH0 values (kcal mol−1) are respectively −4.1 (Cl−), −3.4 (Br−), −3.0 (I−) in AN and −0.7 (Cl−) in DMSO. In contrast to previous literature data there is a linear relationship between these ΔH0 and reported ΔG0 values for the formation of the SO2X− complexes in AN. The difference between the ΔH0 values for SO2Cl− in the solvents AN and DMSO is accounted for by the more exothermic enthalpy of solution of SO2 in DMSO which is the more basic solvent, and by the expected minor difference in the enthalpies of transfer of Cl− and SO2Cl− from AN to DMSO, both dipolar aprotic solvents. Some of the problems connected with the stability order of the SO2X− complexes are discussed in relation to solvent effects and properties of X−.
Crystal and molecular structure of dodecamethylcyclohexaphosphazene, (NPMe2)6
Authors: Oakley Richard T. , Paddock Norman L. , Rettig Steven J. , Trotter James
Published: May 2006

Crystals of dodecamethylcyclohexaphosphazene are triclinic, a = 13.898(1), b = 8.690(1), c = 10.790(1) Å, α = 109.84(1), β = 92.01(1), γ = 106.39(1)°, Z = 2, space group [Formula: see text]. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to a final R of 0.034 and Rw of 0.042 for 4217 reflections with I ≥ 3σ(I). The unit cell contains two independent centrosymmetric molecules which are virtually identical. The 12-membered rings have the 'double tub' conformation. Bond lengths not involving hydrogen have been corrected for libration. Weighted mean bond lengths (rms deviations from the mean in parentheses) are: P—N, 1.593(6), C—P, 1.808(4), and C—H, 0.95(6) Å.
Single crystal electronic spectra of a series of trans nickel(II) complexes with N,N′-diethyl- and N,N′-dimethylethylenediamine
Authors: Lever A. B. P. , London G. , McCarthy P. J.
Published: May 2006

We have measured the polarized crystal spectra at 10 K. of Ni(s-Et2en)2X2, where X = Cl, Br, NCS, and H2O (with Cl, Br, and I counterions) and *-Et2en is N, N'-diethylethylenediamine, and of Ni(s-Me2en)2X2, where X = NCS and NO3, and.s-Me2en is N,N′-dimethylethylenediamine. Transition energies were calculated for D4h symmetry using symmetry adapted functions and a normalized spherical harmonic Hamiltonian. When the differences between calculated and observed band positions are minimized, the ligand-field and angular overlap parameters listed in Table 2 are obtained. The criteria for the band assignments are discussed. The principal conclusions are: (1) The π interactions between Ni(II) and the axial ligands are small in contrast to tetragonal Cr(III) complexes. (2) Equatorial and axial parameters are relatively independent, in contrast to tetragonal Cu(II) complexes. (3) The more basic,s-Et2en exerts a stronger ligand field than,s-Me2en. (4) The σ-bonding strength of the axial ligands follows the spectrochemical series. (5) DQ for the axial ligands in the ethyl complexes is lower than anticipated, probably due to steric hindrance of the bulky ethyl groups. (6) B values are all near 850 cm−1, except for an anomalously low value for Ni(s-Et2en)2(NCS)2.
Studies on metal–acetylene complexes. VII. The molecular structure of bis(tricyclohexylphosphine)(hexafluorobut-2-yne)platinum(0)
Authors: Richardson John F. , Payne Nicholas C.
Published: May 2006

The acetylene complex Pt(P(cyclo-C6H11)3)2 (F3CC≡CCF3) crystallizes in the monoclinic space group P21/c with four formula units in a cell of dimensions a = 10.902(2),b = 21.766(3), c = 19.808(3) Å, and β = 116.52(1)°. Three-dimensional X-ray data were collected on a four circle automatic diffractometer using Cu radiation. The structure was solved by the heavy atom method, and refined by full-matrix least-squares methods on F. A conventional agreement factor of 0.062 was achieved, employing 6678 observations for which I > 0. The coordination geometry at the platinum atom is essentially planar, for the acetylene triple bond makes an angle of 6.5(5)° with the plane formed by the Pt and the two P atoms. The triple bond length is 1.260(10) Å. The acetylene adopts a cis-bent geometry, with a mean bend-back angle of 45.5(8)°. The ligand is considerably perturbed upon coordination to the Pt atom, as is evident from the Δv(C≡C) value of 578 cm−1.
Chemistry of chelocardin II: chemical modifications at C2″ and C12a
Authors: Chu Daniel T. W. , Huckin Stuart N. , Bernstein Edith
Published: May 2006

A selective reduction of chelocardin has been developed leading to 12a-deoxychelocardin which retains much of the antibacterial potency of the parent antibiotic, unlike the analogous reduction of tetracycline. Reaction of an N-protected chelocardin with amide acetals leads exclusively to products in which the condensation has occurred at the methyl group of the acyl side chain.
Nonexistence of the alleged isobindone. The aldol–retroaldol reaction of 1,3-indandione
Authors: Taurins Alfred
Published: May 2006

The existence of the alleged isobindone has been disproved. The compound, mp 330 °C, formed as a byproduct in the aldol–retroaldol condensation reaction of 1,3-indandione is not isobindone but 1-(1,3-indandionyl-2)-3-(1,3-indandionyliden-2)indene. The compound, mp 337 °C, formed from bindone in pyridine solution has the composition C36H18O5.
Spin–lattice relaxation and hydrodynamical rotation of triphenylene
Authors: Wasylishen Roderick E. , Pettitt Brian A. , Danchura Werner
Published: May 2006

The viscosity and temperature dependence of 1H, 2H, and 13C nmr relaxation rates of triphenylene were investigated. The observed η/T dependence of the reorientation correlation time, τc, is compared with that derived from the work of Hu and Zwanzig based on hydro–dynamic rotation with 'stick' and 'slip' boundary conditions. In the hydrodynamic regime,τ = Cη/T. The observed slope, Cexperimental, is 6.2 ± 2 ns K/cP and the calculated values are Cslip = 4.1 ± 0.6 ns K/cP and Cstick = 31.0 ± 3.1 ns K/cP. These data imply that the reorientation of triphenylene obeys a near-slip condition. That is, rotation in the plane of the molecule encounters little resistance, but rotation of the plane of the molecule is resisted by shear forces in the solvent displaced during rotation. Expressions are given for Boltzmann-averaged free rotation times and comparisons are made with the η = 0 intercept and the times for slightly hindered rotation.
Abinitio calculation of the vibrational structure in the electronic spectra of HCN and DCN between 1700 and 2000 Å
Authors: Perić M. , Peyerimhoff S. D. , Buenker R. J.
Published: May 2006

Ab initio SCF and CI calculations for the potential surfaces of HCN in ground and various 1(π,π*) excited states are carried out using an AO basis of double-zeta quality augmented with various polarization functions. These results are then combined with transition moment data to allow for a Franck-Condon analysis of the vibrational structure of the lowest three electronic transitions in both HCN and DCN. The resulting intensity distribution is then compared with the corresponding experimental data reported by Herzberg and Innes. This work confirms the earlier conclusion of Schwenzer et al. that the upper state in the [Formula: see text] band system is the 1∑−−1A″species, and not the 1Δ as originally believed. In addition a detailed mechanism for the observed predissociation of the α state is outlined, in which the gradual conversion of the π* MO of bent HCN into a pure hydrogenic 1s AO plays a key role. Arguments are also presented in favor of assigning the [Formula: see text]transition seen in DCN to a 1Δ-21A′ upper state with the same D + CN dissociation limit as for the 1∑−−1A″ species.
Mise en évidence d'un nouvel acide tungstique en solution. Filiations avec d'autres polytungstates
Authors: Lemerle Jean , Lefebvre Jean
Published: May 2006

A new tungstic acid has been prepared in aqueous solutions by ion exchange. At room temperature gelation occurs in solutions in a few hours, and 3 or 4 days after, the yellow oxide WO3 precipitates. In aqueous solutions, this acid is formed by tetramers of W6O192− units, which give a gel after association. X-ray analyses of tungstic acid in the solid state demonstrate the absence of crystallinity. In hydroorganic medium, tungstic acid is stabilized in solution, but exists in equilibrium with the Y tungstic and hexatungstic (Fuchs) anions. The condensation of the Y acid and one of its reduced forms is discussed. The pure acid forms of hexatungstic (Fuchs) and Y ions are obtained in solutions and in the solid state.
Amino group acidity in nucleotide bases
Authors: Stewart Ross , Harris Madeleine G.
Published: May 2006

The acidities (standard state, water) of the amino groups in 17 N-alkylated derivatives of adenine, guanine, cytosine, and isocytosine have been determined in aqueous DMSO containing base. Adenine methylated at the 9-position is a weaker acid than its 7-methylated isomer by 2.0 pK units and this difference is explained in terms of the known stabilities of the parent tautomers. A similar situation exists with 1- and 3-methylcytosine (ΔpK = 3.3). The position of alkylation of the isocytosine and guanine systems has a small or negligible effect on acidity, again consistent with known tautomeric effects. A modified ribosyl group attached to the 1-position of cytosine has an acid-strengthening effect of 1.9 units, relative to methyl. Of the amino groups involved in nucleotide base-pairing, that in the methyl derivative of guanine has the highest acidity, pKHA = 14.6; those in the cytosine and adenine derivatives have identical acidities, 16.7. An acidity function for purines and pyrimidines is reported for aqueous DMSO containing 0.011 M tetramethylammonium hydroxide (H−P).
Décharge triboélectrique dans le système propane – vapeur d'eau
Authors: Herman Jan A.
Published: May 2006

Gaseous propane containing various amounts of water vapour was subjected to a triboelectric discharge in an apparatus of mercury in borosilicate glass. The extent of decomposition of propane appeared not to depend on the presence of water vapour below a partial pressure of about 2 Torr. Above this pressure of H2O the discharge disappeared. The relative composition of the products of the propane decomposition varied with the concentration of water vapour.
Synthesis of proctolin, a pharmacologically active pentapeptide in insects
Authors: Starratt Alvin Neil , Brown Brian Ellman
Published: May 2006

The synthesis of the pentapeptide H-Arg-Tyr-Leu-Pro-Thr-OH by the mixed anhydride procedure and by the pentafluorophenyl ester method is described. This synthetic peptide is identical to proctolin, a myotropic substance isolated from the cockroach, Periplaneta Americana (L.).
Apparent molal heat capacities and volumes of aqueous electrolytes at 25 °C: NaClO3, NaClO4, NaNO3, NaBrO3, NaIO3, KClO3, KBrO3, KIO3, NH4NO3, NH4Cl, and NH4ClO4
Authors: Roux Alain , Musbally Goolam M. , Perron Gérald , Desnoyers Jacques E. , Singh Prem Paul , Woolley Earl M. , Hepler Loren G.
Published: May 2006

Measurements at 25 °C with flow calorimeters and densimeters have led to heat capacities and densities of aqueous solutions of 11 1:1 electrolytes: NaClO3, NaBrO3, NaIO3, NaNO3, NaClO4, NH4NO3, KClO3, KBrO3, KIO3, NH4Cl, and NH4ClO4. The first 6 salts were studied up to near saturation. We have used results of these measurements to obtain apparent molal heat capacities and apparent molal volumes of the various solutes. Extrapolation to infinite dilution on the basis of the Debye–Hückel theory bas led to [Formula: see text]and [Formula: see text] values for each solute. We have compared these standard values with results of earlier investigations.
Etudes d'hétérocycles pentagonaux polyhétéroatomiques par résonance magnétique nucléaire du 13C. Thiazoles et thiazolo[2,3-e]tétrazoles
Authors: Faure Robert , Galy Jean-Pierre , Vincent Emile-Jean , Elguero José
Published: May 2006

Carbon-13 nmr spectra of 18 thiazoles with different substituents (R = CH3, C6H5, Cl, Br, NH2 et N3) have been recorded. The 13C chemical shifts and the nJ(C,H) coupling constants are discussed as a function of the nature of the substituent and the electronic structure of the thiazole ring. The 2-azido substituted thiazoles show azido-tetrazole isomerism, making possible a comparative study of substituent effects in thiazole and thiazolotetrazole rings. These studies have been extended to other heterocycles: benzothiazole, isothiazole, and isoxazole.
Synthesis of substituted thietanes and thiolanes from α- and β-chloroepoxides and their oxidation to 1,1-dioxides
Authors: Abbott Frank S. , Haya Katsuji
Published: May 2006

Treatment of 3-chloro-1-phenylpropylene oxide-1,2 (7) or 1-chloro-4-phenylbutylene oxide-3,4 (8) with H2S saturated ethanolic NaOEt gave 3-hydroxy-2-phenylthietane (9) and 3-hydroxy-2-phenylthiolane (10) respectively. A similar treatment of 3-chloro-2-phenylpropylene oxide-1,2 (12) at low temperatures gave 3-chloro-2-hydroxy-2-phenylpropanethiol (13); at reflux temperatures or by refluxing 13 in ethanolic NaOEt, 3-hydroxy-3-phenylthietane (14) was formed.Oxidation of 9, 10, and 14 with m-chloroperbenzoic acid or H2O2–HOAc gave the respective 1,1-dioxides 19, 20, and 25. The alcohols 19 and 20 were dehydrated to their corresponding cyclic olefins through the benzylsulfonate esters. Under the conditions of the Ritter reaction 25 dehydrated to the cyclic olefin. Treatment of 19 with mineral acid gave benzyl methyl ketone, while refluxing 19 in base gave benzyl methyl sulfone. Ethoxylation of 2-phenylthiete 1,1-dioxide (23) to the 3-ethoxy derivative 34 was achieved under basic conditions. Attempted chlorination of 9 resulted in desulfurization to 3-chloropropenylbenzene (5).
Résonance magnétique nucléaire du carbone-13 de composes oxa- et azabicyclo[3.3.1]- et -[4.2.1]nonaniques
Authors: Barrelle M. , Apparu M. , Gey C.
Published: May 2006

Carbon-13 nmr spectra have been recorded for 25 oxa- and azabicyclo[3.3.1]- and -[4.2.1]nonanes. Results obtained for the 9-oxabicyclo[3.3.1]nonanes, 2-substituted by hydroxyl or alkyl- and phenylamino groups, as well as those obtained for the N-alkyl- or N-phenyl-9-azabicyclo[3.3.1]nonan-2-ols, provide supplementary information regarding the previously studied structures of these types. Shielding and deshielding due to γ and δ steric interactions were observed depending on the substituent. The study of the oxabicyclo[4.2.1]nonanes, substituted or not substituted in positions 2 and 7 by hydroxyl groups, and of the azabicyclo[4.2.1]nonanes substituted in position 2 by the same group, yields interesting results on the conformational equilibria in these compounds which is caused by the flexibility of the seven-membered ring. The conformational equilibrium is displaced toward the boat form of the seven-membered ring for the unsubstituted compounds. Gauche conformations are proposed for the other compounds in order to account for the experimental observations; the pure chair and boat forms are excluded. Two ketones also have been studied. [Journal translation]
Syntheses related to the octodiose in apramycin. Part II
Authors: Jarrell Harold C. , Szarek Walter A.
Published: May 2006

Derivatives of two octodioses have been synthesized from methyl α-D-glucopyranoside and have been shown to possess a trans-decalin structure. The new octodiose derivatives may be useful in the synthesis of aminooctodioses which occur in apramycin and oxyapramycin.
General method for the synthesis of [n.3.3]propellanes, n ≥ 3
Authors: Weber Robert W. , Cook James M.
Published: May 2006

Reaction of alicyclic-1,2-diones (2a–d) with dimethyl 3-ketoglutarate 1 at room temperature in aqueous buffer (pH = 5.6) provided good yields of the tetramethylpropellanedione tetracarboxylates (3a–d), respectively. Hydrolysis and decarboxylation of the β-ketoester functions, followed by Wolff–Kishner reduction of the corresponding propellanediones (4a–d) has resulted in synthesis of [10.3.3]-, [6.3.3]-, [4.3.3]-, and [3.3.3]propellanes (5a–d). The 13C nmr of propellanes 5a–c are also reported.[Formula: see text]
The synthesis of D,L-cis-N-oxalamido-3-N-phenylacetamido-4-methoxy methyl-2-azetidinone
Authors: Just George , Liak Teng-Jiam
Published: May 2006

The title compound γmax 1810 cm−1, has been synthesized in 18% yield, starting from L-serine.
Thermolysis of Δ3-1,3,4-oxadiazolin-2-ones and 2-phenylimino-Δ3-1,3,4-oxadazolines derived from α,β-epoxyketones. An alternative method for the convers of α,β-epoxyketones to alkynones and alkynals
Authors: MacAlpine Gerald A. , Warkentin John
Published: May 2006

Thermolyses in polar solvents, of Δ3-1,3,4-oxadiazolin-2-ones or 2-phenylimino-Δ3-1,3,4-oxadiazolines derived from α,β-epoxyketones, yields acetylenic carbonyl compounds. Good yields of acetylenic aldehydes and ketones are obtained for those cases in which the epoxide is ring fused. Extension to acyclic cases failed primarily due to predominance of a parallel decomposition pathway. The method complements the procedures developed by Eschenmoser and co-workers for the conversion of, α,β-epoxyketones into acetylenic carbonyl compounds.
The enthaply of formation of potassium chromate(V), K3CrO4(c)
Authors: Johnson Lawrence H. , Hepler Loren G. , Bamberger Carlos E. , Richardson Donald M.
Published: May 2006

Calorimetric measurements on potassium chromate(V), K3CrO4(c), and related substances have provided enthalpies that lead to ΔHf0 = −370 ± 2 kcal mol−1 for K3CrO4(c) at 298 K.
Flow nuclear magnetic resonance study of the addition, dehydration, and cyclization steps for reaction between hydrazine and ethyl acetoacetate
Authors: Cocivera Michael , Woo Kyu W. , Livant Peter
Published: May 2006

The proton nuclear magnetic resonance spectra of a reaction mixture of hydrazine and ethyl acetoacetate (EAA) in aqueous solution under flowing and stopped-flow conditions provides kinetic information concerning the rapid addition step to form the carbinolamine (CA) intermediate and the slower dehydration and cyclization steps to form the anti hydrazone and 3-methylpyrazol-5-one, respectively. The addition step was studied while flowing at rates faster than the dehydration and cyclization rates so that no product signal was observed. Under these conditions, a broad signal resulting from the coalescence of the CH3 proton resonances of EAA and CA is observed. Analysis of the line shape of this broad signal yields the addition rate constant, which has a value that appears to be pH dependent and is of the order of 103 M−1 s−1. Stopped-flow spectra provide the time dependence for the reactant and product signals. Analysis of these time dependences provides information concerning the mechanism of product formation. In contrast with hydroxylamine, CA appears to undergo dehydration and cyclization at comparable rates in the pH range, 8.8–9.2 when hydrazine is the nucleophile. In addition, the anti hydrazone cyclizes at an appreciable rate. These intramolecular cyclization rates are compared with the intermolecular values.
Gas phase acidic solvolysis reactions of acyl halides by ion cyclotron resonance spectroscopy
Authors: McMahon T. B.
Published: May 2006

A number of gas phase ion molecule reactions of protonated species with acyl halides have been examined by ion cyclotron resonance spectroscopy. A number of these reactions are found to involve an addition–elimination reaction having the character of an acidic solvolysis process. Observation of the occurrence or non-occurrence of such reactions and a consideration of appropriate thermochemical data allow a set of criteria to be formulated governing the feasibility of observing the acidic solvolysis reaction. In addition a number of mechanistic inferences are made concerning intermediates involved in the various reactions.
Addition of pseudohalogens to unsaturated carbohydrates. VI. Synthesis of 4′ -thiocordycepin
Authors: Ritchie R. George S. , Vyas Dolatrai M. , Szarek Walter A.
Published: May 2006

The addition of the pseudohalogen iodine nitrate (IONO2) to the endocyclic alkenic bond in benzyl 2-O-benzyl-3,4-dideoxy-α-D-glycero-pent-3-enopyranoside (3) is described. The stereochemistry and regiochemistry of addition were elucidated by chemical degradation, 1Hmr spectroscopy, mass-spectral analysis, and polarimetry. A synthetic route to 4′-thiocordycepin (20) from compound 3, by way of the intermediacy of the preponderant iodine nitrate adduct of 3, namely, benzyl 2-O-benzyl-3-deoxy-3-iodo-4-O-nitro-β-L-lyxopyranoside (4), is also described.
Competitive thermal and photochemical processes in cyclopropylketone rearrangements. II. Thermal isomerization of spiro[n.2]alkan-2-ones
Authors: Khazanie Prabhaker G. , Lee-Ruff Edward
Published: May 2006

Conformationally-rigid methyl-substituted cyclopropyl ketones with a suitably disposed γ-hydrogen undergo thermal type II reactions efficiently. Comparison of yields of these rearrangements with their photochemical analogs suggest that photochemical type II reactions arise from excited vibrational states. In the absence of a suitably disposed γ-hydrogen, and if strain factors permit, such systems undergo oxovinylcyclopropane to dihydrofuran rearrangement. The inertness of these systems to undergo such thermal rearrangement increased on going from cyclohexanone to the cyclopentanone series.
Polyol–protein interactions. Thermodynamical evidence for a selective solvation of glycerol and hexitols by aqueous β-lactoglobulin
Authors: DiPaola Giuseppa , Belleau Bernard
Published: May 2006

Apparent specific heat capacities and volumes of the protein β-lactoglobulin have been determined under a variety of solute–solvent and solvent–cosolvent compositions. These quantities were derived from measurements of volumetric specific heats and densities with a flow microcalorimeter and flow densimeter. The effect of homologous polyols on the isothermal denaturation of the protein by urea at 25 °C was investigated. The results suggest that polyol binding on the protein is sensitive to structural effects, maximum discrimination being exerted in favor of glycerol and its doubles, the hexitols.
Gas phase dissociation of protonated acetic acid to the acyl cation and water. Heat of formation of CH3CO+ and proton affinity of ketene
Authors: Davidson William R. , Lau Yan K. , Kebarle Paul
Published: May 2006

Pulsed electron beam high pressure mass spectrometry was used to measure the enthalpy and entropy of the dehydration of protonated acetic acid, and the proton affinity of ketene in the gas phase. The variation of the equilibrium constant with temperature from 515 to 615 K led to ΔH0 of 24.6 kcal/mol and a ΔS0 of 33.1 cal/deg for the dehydration of protonated acetic acid. Proton transfer equilibria measurements of reactions: BH+ + CH2CO = B + CH3CO+ at 600 K with reference bases of known proton affinity led to a proton affinity of 195 kcal/mol for ketene. The heat of formation of the acetyl cation (ΔHf0(CH3CO+) = 160) was obtained from both the proton affinity of ketene, and from the dehydration enthalpy of protonated acetic acid combined with the proton affinity of acetic acid. The energetics for the dehydration reaction in the gas phase and in solution are compared.
The oxidation of haplophytine
Authors: Yates Peter , MacLachlan Frederick N. , Rae Ian D.
Published: May 2006

Oxidation of haplophytine (1) with alkaline potassium permanganate has been shown to give the seco product 16. This assignment is based on spectroscopic data and comparison of these with spectroscopic data for the analogous seco product 8 formed on similar oxidation of aspidophytine (3), an acid cleavage product of haplophytine. The course of these oxidations contrasts with that of the oxidation of haplophytine and aspidophytine with alkaline hydrogen peroxide, which gives 4 and 6, respectively, without carbon–carbon bond cleavage.
Formation and reactivity of the aminothiyl and iminothiyl radicals by means of flash photolysis
Authors: Ito Osamu , Matsuda Minoru
Published: May 2006

Flash photolysis of bis[piperidyl-1] disulfide gave a clear transient band at 340 nm and a weak band around 525 nm, which were assigned to the piperidyl-1-thiyl radical. In a similar manner, bis[diphenylimino] disulfide gave a transient band at 420 nm, which could be assigned to the diphenyliminothiyl radical. These radicals disappeared in various solvents according to second-order kinetics with rate constant 0.8–7.2 × 109 M−1 s−1 showing that the radicals decay predominantly by recombination with diffusion controlled rates. These radicals were not reactive toward oxygen, olefins, organophosphorous compounds, and hydrogen donors in agreement with the results given by the kinetic epr study reported by Maillard and Ingold.
A study of the adsorption of formic acid and related molecules onto evaporated copper films, both clean and oxide-covered, by infrared ellipsometric spectroscopy
Authors: Stobie Robert William , Dignam Michael John
Published: May 2006

Species formed on evaporated copper surfaces, both clean and oxide-covered, were examined using ir ellipsometric spectroscopy (IRES). Spectra were obtained for CO adsorbed on both bare and oxide-covered copper, the spectra being in accord with published data. No spectra were observed for formic acid adsorption unless free oxygen was present, in which case a spectrum characteristic of a carbonate species was found. Supporting data were obtained to show that the carbonate species was formed by reaction of formic acid and oxygen on the oxide-covered surface. These data illustrate some of the unique advantages of IRES for studying molecular processes on surfaces.
The reductive denitration of carbohydrate α-nitroepoxides by sodium borohydride
Authors: Baer Hans H. , Madumelu Chukwuemeka B.
Published: May 2006

Action of sodium borohydride upon sugar derivatives that contain an α-nitrooxirane grouping leads to reductive denitration producing high yiel ds of α-hydroxy-β-deoxy derivatives. Thus, 5,6-anhydro-1,2-O-isopropylidene-6-nitro-α-D-glucofuranose (2) gave 5-deoxy-1,2-O-isopropylidene-α-D-xylo-hexofuranose (3). The methyl 2,3-anhydro-4,6-O-benzylidene-3-nitrohexopyranosides having the β-D-talo (4), β-D-allo (5), and β-D-manno (6) configurations readily afforded methyl 4,6-O-benzylidene-2-deoxy- β-D -lyxo-hexopyranoside (10; from 4) and its β-D-arabino isomer (11; from 5 and 6). The corresponding nitroepoxy glycoside of α-D-talo configuration (7) reacted more slowly and gave a mixture of 3-epimeric 2-deoxyglycosides, the analogous α-D-lyxo (13) and α-D-xylo (14) compounds. The α-D-manno (8) and β-D-gulo (9) nitroepoxides proved unreactive under the same conditions. Stereochemical factors considered to be important in these denitrations are discussed.
Fluidities and conductances of glass-forming melts of cadmium nitrate tetrahydrate and transition metal chlorides
Authors: Islam N. , Kumar S. , Singh K. P.
Published: May 2006

The temperature dependences of fluidifies and equivalent conductances of Cd(NO3)2•4.1H2O–(Ni/Co)Cl2 melts have been explained in terms of Vogel–Tammann–Fulcher and Adam–Gibbs equations. The differences in the values of the glass transition temperatures and the preexponential factors corresponding to the Ni2+ and Co2+ melts were attributed to the differences in the masses of the two Systems. The linear decrease and increase observed in the values of the preexponential factor and the glass transition temperature, respectively, with increasing concentration of the solute were discussed. The overall composition dependences of transport properties were analyzed using expressions derived on the basis of both the above equations.
ESCA spectra and molecular charge distributions for some pyrimidine and purine bases
Authors: Peeling James , Hruska Frank E. , McIntyre N. Stewart
Published: May 2006

A series of pyrimidine and purine bases bas been studied experimentally by electron spectroscopy for chemical analysis. Individual component peaks in the spectra were assigned on the basis of known substituent effects on core electron binding energies. Binding energies for all the core levels in the molecules provide sufficient data to determine the molecular charge distributions. The results compare favourably with atomic charges determined theoretically in the CNDO/2 molecular orbital formalism.
Carbon-13 nuclear magnetic resonance studies of (Z)-5-fluoro-2-methyl-1-{[p-(methylsulfinyl)phenyl] methylene}-1H-indene-3-acetic acid (sulindac) and some related compounds
Authors: Douglas Alan Wilmot
Published: May 2006

Carbon-13 nuclear magnetic resonance spectra have been obtained and fully assignee for a number of 2-methyl-1-{[p-(methylthio) or -(methylsulfinyl}phenyl]methylene}-1H-indene-3- acetic acid derivatives, including the potent anti-inflammatory compound sulindac, 1Z. Paired E and Z isomers were studied along with the sulindac sodium salt and ethyl ester in the Z series. Variations in steric crowding in E vs. Z isomers produce chemical shift effects which alternate with the number of intervening bonds. Fluorine substituent effects and 19F nuclear spin coupling to 13C nuclei, second-order features in off-resonance proton-decoupled spectra, and values of long-range 13CH nuclear spin coupling constants have been employed in making a complete set of assignments.
Diterpene chemistry. VI. Some chemistry of 8,14-epoxypimaric acid. Comments on the biosynthesis of tetracyclic diterpenes
Authors: ApSimon John W. , Hall Steven F.
Published: May 2006

The cleavage of methyl pimarate 8,(14) α-epoxide (4) was studied with a variety of acidic reagents. The major products observed were the corresponding Δ7,8-14α-alcohol and dienes. Participation of the vinyl group was not detected.Consideration of the stereoelectronic requirements for cyclisation of olefins with carbonium ions at C-8 of the pimarane skeleton suggest that the pimaranes are not the biogenetic precursors of the tetracyclic diterpenes. A modification of the traditional route is presented as a working hypothesis.
Oxidative cyclization of carbonyl derivatives. 5-Imino-Δ1-1,2,4-triazolines from alkylideneimino guanidines
Authors: Cabelkova-Taguchi Lubomira M. , Warkentin John
Published: May 2006

Treatment of 2-propylideneimino guanidinium acetate with lead tetraacetate, in methylene chloride containing solid sodium carbonate, afforded the previously unknown 3,3-dimethyl-5-imino-Δ1-1,2,4-triazoline. Similarly, N,N′-diphenyl-N″-(2-propylideneimino)guanidinium acetate afforded Z-4-phenyl-5-phenylimino-Δ1-1,2,4-triazoline as the major oxidation product and the corresponding E isomer as a minor product. Stereochemistry was established spectrophotometrically and also by isomerizing the minor (E) isomer to the major (Z) isomer.
Thermodynamic properties of the alkali metal hexachloroniobate and hexachlorotantalate compounds by vapour pressure measurements
Authors: Sadoway Donald R. , Flengas S. N.
Published: May 2006

The vapour pressures for the decomposition of the solid and liquid compounds AMCl6 where A = Na, K, Rb, or Cs, and M = Nb or Ta, were measured by a fused quartz Bourdon spiral pressure gauge. The hexachlorotantalates were found to be more stable thermally than the hexachloroniobates. Enthalpies of decomposition were calculated. The dissociation temperatures of each sequence of compounds increase with increasing size of the radius of the alkali-metal cation. Partial pressures of NbCl5 or TaCl5 vapour in equilibrium with solutions representing the binary Systems KCl–KNbCl6 and KCl–KTaCl6, respectively, are also reported.
Stereochemistry and mechanisms of the reactions of acylsilanes with alkoxides
Authors: Brook Adrian G. , Vandersar Teunis J. D. , Limburg William
Published: May 2006

Using chiral NpPhMeSiCOMe it is shown that the 'cleavage' pathway for the reaction of alkoxides with acylsilanes involves nucleophilic attack at the carbonyl group, followed by subsequent rearrangements which result in optically active NpPhMeSiOR and aldehyde. The 'rearrangement' pathway involves stereospecific migrations of the naphthyl and phenyl groups from silicon to different faces of the adjacent carbonyl group, resulting in chiral naphthylethanol and phenylethanol of opposite absolute configurations.
Nuclear analogs of β -lactam antibiotics. IX. Synthesis of 7-methoxy 2-isocephems and O-2 isocephems
Authors: Douglas James L. , Horning Donald E. , Conway Terry T.
Published: May 2006

The syntheses of 7-methoxy-7-phenoxyacetamido-3-methyl-Δ3-isocephem-4-carboxylic acid 11a, 7-methoxy-7-phenoxyacetamido-3-rnethyl- Δ3-O-2-isocephem-4-carboxylic acid 11b and 7-methoxy-7-(2-thienyl)acetamido-3-acetoxymethyl- Δ3-O-2-isocephem-4-carboxylic acid 11c are described. A sequence analogous to that used to prepare 7-methoxy cephalosporins was used: Schiff base anions were thiomethylated and the Schiff bases hydrolyzed to free amines. The amines were acylated and thiomethyl to methoxyl conversion effected with mercuric ion catalysis. Removal of protective esters gave the acids 11a, 11b, and 11c. Compound 11c showed a modest level but broad spectrum of antibacterial activity.
Reaction of dimethyl sulfoxide with chlorothiolformates, hydrogen chloride, hydrogen fluoride, and hexafluoroisopropanol
Authors: Queen Alan , Lemire Alberta E. , Janzen Alexander F. , Paddon-Row Michael N.
Published: May 2006

Dimethyl sulfoxide reacts with phenyl chlorothiolformate according to the stoichiometry:[Formula: see text]p-Chlorophenyl and tert-butyl chlorothiolformate appeared to react in a similar manner. The 1:1 hydrogen chloride adduct Me2SO:HCl was characterized by elemental analysis and proton and carbon nmr. A cryoscopic molecular weight determination of the adduct Me2SO:HOCH(CF3)2 showed it to be monomeric at low concentrations but associated at higher concentrations, suggesting a monomer–dimer equilibrium. The 1:2 adduct Me2SO:2HF is formed by the addition of anhydrous HF to dimethyl sulfoxide.
Synthesis and stereochemistry of 2-pyrone derivatives related to some fungal metabolites
Authors: Lesage Suzanne , Perlin Arthur S.
Published: May 2006

Some stereochemistry of 'asperlin' (1) and related fungal metabolites containing a 5,6-dihydro-2-pyrone moiety, has been deduced through correlation of nmr and ord parameters with those of reference compounds derived from carbohydrates of known stereochemistry. The reference compounds are 4,6-di-O-acetyl-2,3-dideoxy-D-threo- and -D-erythro-hex-2-enono-1,5-lactones obtained by modification of D-galactal and D-glucal, respectively, and the D-enantiomer of 1, synthesized in a multistep sequence from D-galactose. It is shown that the 5,6-substituents of the pyrone ring of 1 have the L-threo configuration and also that the exocyclic epoxypropyl moiety is trans.
Mechanism of bromination of a quaternary pyrimidinium cation. Change of rate determining step with acidity
Authors: Tee Oswald S. , Thackray David C. , Berks Charles G.
Published: May 2006

The kinetics of bromination of the 1,2-dihydro-1,3-dimethyl-2-oxopyrimidinium cation (Q+) in aqueous media (pH 0–5) have been studied using the stopped-flow method. At the higher acidities (pH < 2) the results are consistent with rate determining attack by bromine upon the pseudobase (QOH), whereas at low acidities (pH > 4) it appears that pseudobase formation is rate determining. The change occurs because at high acidity the reversal of the pseudobase QOH to the cation is fast relative to bromine attack, whereas at low acidity the converse is true. Results obtained at intermediate acidities (pH 2–4) are consistent with this interpretation.A separate kinetic study of pseudobase formation (and decomposition) yielded rate constants in good agreement with those derived from the bromination study.
Stéréochimie de β-diols et de leurs dérivés cycliques. X. Etude structurale en résonance magnétique nucléaire du proton de dioxanne-1,3-4-spirocyclohexanes: méthyl-2 dioxanne-1,3-4-spiro-tert-butyl-4′ cyclohexanes-cis et -trans (série I)
Authors: Cazaux Louis , Gorrichon Jean-Pierre , Maroni Pierre , Perry Marcel
Published: May 2006

The two title compounds serve as models for an eventual structural study of two more complex series. High field nmr spectral analysis using INDOR or solvent effects allows us to assign nearly all proton signals and to propose that these compounds exist in the double chair conformation. Finally, chemical shifts in CCl4 have been used to evaluate the effect of the intracyclic oxygen atoms on the 2′ and 6′ proton nmr resonances of the spirobicyclohexane. [Journal translation]
2,3-(1′-Pyrazolino-3′,4′) hexopyranosides and their products of decomposition
Authors: Baer Hans H. , Linhart Friedrich , Hanna Hanna R.
Published: May 2006

The methyl 4,6-O-benzylidene-2,3-dideoxy-3-nitrohex-2-enopyranosides having the β-D-erythro (1), α-D-erythro (2), β-D-threo (3), and α-D-threo (4) configurations reacted with diazomethane to give high yields of 2,3-(1′-pyrazolino-3′,4′) derivatives (5–8). The pyrazolines 5 and 6 (from 1 and 2) were deduced on the basis of nuclear magnetic resonance and optical rotatory dispersion data to possess the β- and α-D-gluco configurations, and 7 and 8 (from 3 and 4), to have the β- and α-D-ido configurations, respectively. Thermolysis of 5, 6, and 8 led to the methyl-branched, nitroolefinic glycosides 9, 10, and 11 (the 2-C-methyl derivatives of 1, 2, and 4), whereas 7 afforded the corresponding 2,3-C-methylene derivative 12, a cyclopropano sugar. The α-anomeric cyclopropano derivative 13 was obtained from 8 by decomposition on silica gel.
Carbon-13 spectra of 2,5-dihydrothiophenes and their 1,1-dioxides
Authors: McIntosh John M.
Published: May 2006

The complete carbon-13 nmr spectra of 16 alkylated 2,5-dihydrothiophenes and 10 sulfones derived from them are reported. No significant interactions between C-2 substituents and C-5 are noted and stereochemical determinations based on this γ effect are not possible. On oxidation to the sulfones, C-2 and C-5 are dramatically deshielded but C-3 and C-4 are shielded. A possible explanation for this effect is presented.
The enol content of simple carbonyl compounds: a thermochemical approach
Authors: Guthrie J. Peter , Cullimore Patricia A.
Published: May 2006

From the heats of hydrolysis of enol ethers, the heats of formation of the enol ethers, and thence the free energies of formation of the enol ethers in aqueous solution can be calculated. For this calculation it was necessary to determine the free energies of transfer from the gas phase to aqueous solution. By methods previously published it was possible to estimate the free energy change for the hypothetical hydrolysis reaction leading from the enol ether to the enol, which in turn made possible calculation of the free energy of formation of the enol. Finally the free energy change for enolization in aqueous solution could be calculated using the known free energy of formation of the corresponding keto tautomer. In this way the following were determined: carbonyl compound, pKenol = −log ([enol]/[keto]): acetaldehyde, 5.3; propionaldehyde, 3.9; isobutyraldehyde, 2.8; acetone, 7.2; 2-butanone, 8.3; 3-pentanone, 7.8; cyclopentanone, 7.2; cyclohexanone, 5.7; acetophenone, 6.7.