bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of Lambertianic Acid
Authors: Bell R. A. , Gravestock M. B. , Taguchi V. Y.
Published: May 2006

A synthesis of lamberlianic acid 2a starting from podocarpic acid is described. The central intermediate, diester-ketone 4b, is obtained by ozonolysis and hydrogenation, and the exocyclic methylene group in ring B generated via a Reformatsky reaction. The furan ring is attached by nucleophilic attack of 3-lithiofuran, for which an improved preparation is described, on either the acid chloride 7b or the aldehyde 16. The 12-oxygen atom is removed by mesylation of the alcohols 12a and b and Li–liquid ammonia reduction.
Kinetics of the Anation Reaction of Nickel(II) and 1,10-Phenanthroline in Ethanol
Authors: Sanduja M. L. , Smith W. MacF.
Published: May 2006

The kinetics of formation of the monophenanthroline complex of nickel(II) in ethanol has been studied using stopped-flow methods over the temperature range 7 to 35 °C. Tetrabutyl ammonium perchlorale in concentration 0.044 M does not affect the rate appreciably, sodium perchlorate at the same concentration depresses the rate significantly. Most measurements were made in the absence of electrolytes other than nickel perchlorate and a trace of perchloric acid. The second order rate constant is not significantly dependent on the nickel(II) concentration over a four-fold change in value indicating that the concentration of encounter pairs is small relative to the concentration of the free reactants. The rate constant at 25 °C (31 × 103 M−1 s−1)is consistent with a dissociative interchange mechanism and the rate constant for ethanol exchange on nickel. However, the value of ΔH≠ for the overall reaction (15.9 ± 1.0 kcal mol−1) is about 5 kcal mol−1 higher than that reported for ethanol exchange.
Cancentrine. IV. Acetolysis Products of Cancentrine Methiodide
Authors: Rodrigo R. , Manske R. H. F. , Smula V. , MacLean D. B. , Baczynskyj L.
Published: May 2006

Treatment of cancentrine methiodide with boiling acetic anhydride in the presence of sodium acetate gave two highly unsaturated products formed in rearrangement reactions. One of the products retained all the original carbon and both nitrogen atoms of cancentrine while the other formed with loss of three carbon atoms and one nitrogen atom. The structures of the two compounds were deduced through analysis of their p.m.r. spectra and through comparison of their p.m.r. and u.v. spectra with those of model compounds synthesized in this study. A mechanism for the formation of the rearrangement products is proposed and discussed.
The Vacuum Ultraviolet Photolysis of Cyclopentanone
Authors: Scala Alfred A. , Ballan Daniel G.
Published: May 2006

In the vacuum ultraviolet photolysis of cyclopentanone, the major modes of fragmentation of the electronically excited ketone are:[Formula: see text]The sum of the quantum yields for reactions A and B is 0.87 at 147.0 nm and these reactions become less important as the incident energy is increased. A pressure study at 147.0 nm of the partitioning of the tetramethylene diradical between paths A and B indicates that the ratio kA/kB is approximately 8. The quantum yield for reaction 8 is only 0.02. The remainder of the decomposition of cyclopentanone is accounted for by reactions 4 and 5, which appear to become more significant as the incident energy increases. The mechanisms for reactions 6 and 8 are best interpreted in terms of diradicals of structure (CH2)n where n = 1, 3, and 4. The lack of non-acyl σ-cleavage at 147.0 nm is an indication that the absorption of energy occurs at the carbonyl group.
Triplet Charge Transfer Complex between Excited Electron Acceptor and Ground State Electron Donor
Authors: Loutfy Rafik O. , Loutfy Raouf O.
Published: May 2006

The half-wave reduction and oxidation potentials, E1/2's, of carbonyl compounds and amines, respectively, are used to estimate the location of triplet charge transfer states (CT). A linear free-energy relationship between the calculated CT triplet energies and the corresponding carbonyl molecules triplet energies was obtained. It has also been found that the free energy change (ΔF) for CT complex formation correlate with the triplet carbonyl quenching rate constant kq.
The Synthesis of 1-Benzyl-2-carbomethoxy-3,3-dimethyl Aziridine and its Ring Opening with Excess Acids
Authors: Berse Casimir , Bessette Pierre
Published: May 2006

The synthesis of 1-benzyl-2-carbomethoxy-3,3-dimethyl aziridine and its ring opening with various excess acids such as hydrogen chloride, acetic, propionic, and thioacetic acids and benzyl mercaptan are herein described.
The Mass Spectra of Imidoyl Halides and Bromoiminium Bromides
Authors: Gal J. , Phillips B. A. , Smith R.
Published: May 2006

The mass spectra of imidoyl halides 1–6 and bromoiminium bromides 7–9 have been studied and their fragmentation pattern discussed. Loss of halogen atom from the molecular ion of imidoyl halides to form a N-alkylnitrilium ion is a major process. When the N-alkyl group is larger than methyl the fragmentation of N-alkylnitrilium ions with hydrogen rearrangement to give the [PhC≡NH]+ ion becomes important. Thermolysis of bromoiminium bromides in the inlet system of the mass spectrometer produces imidoyl bromides via dealkylation (or dehydrobromination) and α,α-dibromobenzylamines via addition of bromide to the C=N bond.
The Reaction Between Certain Organometallic Reagents and Benzanthrone
Authors: Allen C. F. H.
Published: May 2006

The action of certain organometallic reagents upon benzanthrone (7H-benz[de]anthracene-7-one) has been further investigated. Some of the components were identified, and the nature of hitherto unknown compounds was deduced. Phenylmagnesium chloride in tetrahydrofuran gave nearly double the yield of crystallizable products. The primarily-formed enol, formed by 1,4-addition and related to the principal product, 6-phenylbenzanthrone, was isolated and identified. In the presence of cuprous and cobaltous chlorides unexpected products were indicated. The formation of 3-phenylbenzanthrone is assumed to be the result of a 1,8-addition. Phenyllithium gave all the above and many others. Among them was the carbinol, formed by 1,2-addition, and a new hydrocarbon, 7-phenyl-7H-benzanthrene.
Carbon-13 Magnetic Resonance: Diterpenoid Alkaloids From the Delphinium Species
Authors: Jones Alan J. , Benn M. H.
Published: May 2006

The carbon-13 magnetic resonance spectra of the diterpenoid alkaloids lycoctonine (1), deoxylycoctonine (2), deoxymethylenelycoctonine (3), browniine (4), isolatizidine (5), delphonine (6), lycoctonal (7),and their corresponding hydrochloride or perchlorate salts have been determined at 22.63 MHz in the Fourier mode. With the aid of proton decoupling techniques, additivity relationships and the effects induced by specific structural changes, self-consistent assignments of nearly all the resonances have been made. Substituent effects are often of the same order but differ in magnitude from those for simpler systems reported in the literature. The effects of protonation do not unambiguously follow the additive trends indicated in simpler systems but do exhibit a reasonably constant pattern. The data have been applied in the structural elucidation of two previously unknown bases isolated from Delphinium bicolor Nutt.
The Mutarotation of Glucose in Dimethylsulfoxide and Water Mixtures
Authors: Ballash N. M. , Robertson E. B.
Published: May 2006

The mutarotation of glucose is a general acid – base-catalyzed reaction which involves two proton transfers. Whether these proton transfers are carried out in a stepwise or concerted manner, the latter alternative possibly incorporating several water molecules in a cyclic transition state, is not known with certainty.This study was undertaken in an attempt to clarify the mechanism by determining directly the number of water molecules participating in the transition state. The method chosen was to determine rates for the acid-catalyzed mutarotation of glucose as a function of solvent composition in dimethylsulfoxide and water mixtures, particularly in the water poor region. The results show that for the acid-catalyzed reaction the order with respect to water is zero. For water catalysis, the results are less reliable but suggest that about three water molecules may be involved. These facts are interpreted to mean that a stepwise mechanism is operative in the proton-catalyzed reaction, but that the solvent-catalyzed process may involve a cyclic concerted mechanism.Rate measurements were also carried out as a function of temperature for various solvent mixtures. The calculated activation parameters remain practically constant over the solvent composition region and attest to the constancy of the mechanism over this range. Thus the results which pertain strictly to solutions of high dimethylsulfoxide content should apply to aqueous solutions as well.
Studies on Horseradish Peroxidase. XII. A Kinetic Study of the Oxidation of Sulfite and Nitrite by Compounds I and II
Authors: Roman R. , Dunford H. B.
Published: May 2006

The kinetics of the oxidation of sulfite and nitrite by horseradish peroxidase compounds I and II have been studied as a function of pH at 25° and ionic strength 0.11. The pH dependence of the rate of the reaction between compound I and sulfite over the pH range 2–7 is interpreted in terms of two ground state enzyme dissociations with pka values of 5.1 and 3.3, and that for the compound II reaction with sulfite in terms of a single ground state enzyme dissociation with a pKa value of 3.9. Whereas the reaction between compound I and sulfite produces the native enzyme without the intermediate formation of compound II, the reaction of compound I with nitrite yields compound II. The second-order rate constants for the reactions of compounds I and II with nitrite increase linearly with increasing hydrogen ion concentration over the pH range 6–8.
The Kinetics of the Ethanolysis Reaction of Some 4-Nitro-substituted Triphenylmethyl Chlorides
Authors: Kulin Eleanor L. , Leffek K. T.
Published: May 2006

The kinetics of the ethanolysis of three triphenylmethyl chlorides, the 4-nitro, 4,4′-dinitro, and 4,4′,4″-trinitrophenylmethyl compounds, have been studied. The effect of change in substrate and solvent composition on the activation parameters, ΔH≠ and ΔS≠, has been determined. For these compounds, ΔH≠ appears to be controlled by substrate structure while ΔS≠varies predominantly with solvent composition.The attempted reaction of pyridine with 4,4′,4″-trinitrophenylmethyl chloride to form the quaternary ammonium salt is also reported.The reactions are interpreted to be proceeding via a carbonium ion-pair mechanism.
Photolyse de pentène-1 dans l'ultraviolet à vide
Authors: Perrin Patrick M. , Collin Guy J.
Published: May 2006

Photolysis of 1-pentene molecules at 8.4 eV (xenon photolysis) and 10.0 eV (krypton photolysis) was studied. Excited molecules decompose to produce mainly ethylene, propadiene, 1,3-butadiene, acetylene, and other minor products. Hydrogen atoms add to the double bond of the monomer and the resulting excited pentyl radical decomposes at low pressure (P < 1 Torr) into propene and ethyl radical. Isomerization of excited 1-pentene molecules is unimportant at these energies.
Some Electron Spin Resonance Observations in the Photoreduction of Nitrobenzenes
Authors: Wong S. K. , Wan J. K. S.
Published: May 2006

The photoreduction of some nitrobenzenes in various organic solvents was re-investigated by e.s.r. and the rapid scan e.s.r. method. The present study resolved the contradicting e.s.r. assignments of the radical observed in the photoreduction of nitrobenzene in tetrahydrofuran and confirmed the identification of the radical [Formula: see text]. All other radicals observed in various solvents were identified and their formation can be explained by secondary processes in the photoreduction.
Marine Organic Chemistry. I. Isolation of 3β,6α-Dihydroxy-5α-pregn-9(11)-en-20-one from the Saponins of the Starfish Asterias forbesi. A Rapid Method for Extracting Starfish Saponins
Authors: ApSimon John W. , Buccini John A. , Badripersaud Satyanand
Published: May 2006

The major aglycone from the saponins of Asterias forbesi has been identified as 3β,6α-dihydroxy-5α-pregn-9(11)-en-20-one (1). A simplified procedure for extracting saponins from starfish is reported which reduces the required working time from 7–14 to 1–3 days.
Investigations of Substituent Effects by Nuclear Magnetic Resonance Spectroscopy and All-valence Electron Molecular Orbital Calculations. II. 4-Substituted α-Methylstyrenes and α-t-Butylstyrenes
Authors: Hamer Gordon K. , Peat Ian R. , Reynolds W. F.
Published: May 2006

Substituent-induced 1H chemical shifts (S.C.S.) for 19 4-substituted α-methyl- and α-t-butylstyrenes have been determined at infinite dilution in C6H12 and 13C S.C.S. have been determined for 0.4 M solutions in CCl4. S.C.S. are correlated with field and resonance substituent parameters and compared with charge densities determined by CNDO/2 MO calculations. The variation of S.C.S. with the dihedral angle, ρ, between phenyl and vinyl groups and the overall pattern of S.C.S. can be largely accounted for by a model of substituent effects based on field, resonance, and π polarization effects, with conjugative interactions varying as cos2ρ. Both 13C chemical shifts and charge densities indicate that the π polarization effect consists of two components: (1) a through-space polarization of the vinyl system by the polar C—X bond and (2) polarization of the entire conjugated styrene π electron system. However, significant deviations are noted for some of the 1H S.C.S. correlations. The CNDO/2 calculations indicate that these deviations are primarily due to electronic effects not predicted by the model outlined above. CNDO/2 calculations for related compounds provide a partial explanation by indicating that the magnitude of the field effect depends upon the nature of the molecular framework.
Vibrational Spectra and Rotational Isomerism in 2-Mercaptoethanol
Authors: Nandy S. K. , Mukherjee D. K. , Roy S. B. , Kastha G. S.
Published: May 2006

From the Raman and i.r. spectra of 2-mercaptoethanol in the liquid state and the temperature variation of the intensity of the Raman lines, it has been concluded that both the trans- and gauche-isomers are present in the liquid. A tentative analysis of the vibrational frequencies of the isomers has been presented.
Vicinal Electron Pairs and Conformation in Six-membered Rings. Some Evidence from the 1,3,2-Dioxathianes
Authors: Wood Gordon , Srivastava R. M. , Adlam B.
Published: May 2006

Barriers to ring reversal (ΔG≠) at the n.m.r. coalescence temperature are reported for a series of 1,3,2-dioxathianes. The value for 1,3,2-dioxathiane-4,4,6,6-d4 of 11.2 kcal/mol is compared with the corresponding values for cyclohexane and various six-membered rings with and without vicinal electron pairs. The 1,3,2-dioxathiane system is suggested as a model for trimethylene sulfites, where the strong preference of the exocyclic oxygen for the axial position interferes with barrier determination by n.m.r. techniques.
Mass Spectrometry of Some Substituted 2-Benzylidenecyclohexanone Oximes
Authors: Smith P. J. , Dimmock J. R. , Turner W. A.
Published: May 2006

The mass spectra of several substituted 2-benzylidenecyclohexanone oximes have been determined at 70 eV and at lower ionization voltages. The major fragmentation pathways for the oximes are loss of the ortho substituent from the parent ion as well as loss of hydroxyl radical. The facility of loss of the ortho substituent is compared with a similar process involved in the fragmentation of substituted 2-benzylidenecyclohexanones. In addition, the mass spectrum of the acetate of 2-benzylidenecyclohexanone oxime was determined and showed a M – 1 peak and also a peak corresponding to the parent oxime formed by loss of ketene.
A Stereochemical and Kinetic Study of the Conversion of Methyl Cyclopropyl Ketones to 4,5-Dihydrofurans
Authors: McGreer Donald Edward , McKinley James William
Published: May 2006

The thermal and photochemical conversion of (1R*,2R*,3S*), (1S*,2R*,3S*), and (1S*,2R*,3R*)-1-acetyl-1,2-dimethyl-3-phenylcyclopropane (1, 2, and 3) to cis- and trans-2,3,4-trimethyl-5-phenyl-4,5-dihydrofurans has been studied. Concurrent with this reaction is an equilibration of 1, 2, and 3, a thermal ring opening of 1 by a 1,5-hydrogen shift, and a cyclopropane-to-propene type reaction under the photochemical conditions. The dihydrofuran from 1 and 2 by the thermal and photochemical conditions is 97% trans- and 3% cis- corresponding to predominant retention at the migrating carbon. The dihydrofuran formed from 3 by the thermal and photochemical reaction is 85% cis- and 15% trans- again corresponding to predominant retention. A kinetic study of the rearrangement of 1-acetyl-1-methyl-2-phenylcyclopropane to 1,2-dimethyl-5-phenyl-4,5-dihydrofuran provides Ea of 48.1 kcal/mol and log A of 14.9 for this first order reaction in the temperature range of 255–288 °C.It is concluded that the thermal and photochemical reactions occur by a non-concerted process through a common 1,3-diradical intermediate in which bond rotation and ring closure steps are competitive.
Dissymmetric Oxidation With Methyl 4-Tolyl (R)-Sulfoxide
Authors: Benn M. H. , Christensen Patricia , Kjersgaard Dan , Watanatada Churai
Published: May 2006

Methyl 4-tolyl (R)-sulfoxide can be used to oxidize (±)-borneol by the carbodiimide–sulfoxide procedure: (−)-camphor is formed in low optical yield; and the residual borneol is correspondingly enriched with its (+)-(1R,2S,4R)-enantiomer.
The Synthesis of gem-Halonitro Sugars and Their Conversion into Epoxynitro Sugars
Authors: Baer Hans H. , Rank Werner
Published: May 2006

Halogenation of methyl 4,6-O-benzylidene-3-deoxy-3-nitrohexopyranosides having the α-D-talo, β-D-galacto, and α-D-galacto configurations, and of the 2,3-dideoxy-3-nitro β-D-lyxo and α-D-lyxo analogs, smoothly furnished 3-halo-3-deoxy-3-nitro derivatives. The glycosides were chlorinated in methanolic solution with aqueous sodium hypochlorite, and similarly brominated with either bromine in the presence of alkali or N-bromoacetamide in the presence of sodium acetate. The analogous nitro glycosides having the β-D-arabino, β-D-manno, α-D-manno, and β-D-gluco configurations and also the 2-acetates of the last three compounds were brominated likewise whereas the α-D-gluco isomer and its 2-acetate were resistant under the conditions examined. The preferred C-3 configuration in the halonitro products appeared to be that which has an equatorial nitro group and an axial halogen atom in the normal pyranose chair conformation (4C1). In most instances the halogenation was found to be highly stereoselective in that sense although in some cases the inverse C-3 epimer was formed in a minor proportion. Base treatment of some of the halohydrins led to 2,3-anhydro-3-nitro glycosides. Such epoxide formation may be associated with epimerization at C-2 and -3, for which a mechanism involving a retrograde Henry reaction is postulated.
Commentaire: Observation par spectrometrie infrarouge d'une reaction parasite lors de la reduction de l'acide hexachloroplatinique
Authors: Primet Michel , Mathieu Michel-Vital
Published: May 2006

During the preparation of supported platinum by hydrogen reduction of hexachloroplatinic acid, the hydrochloric acid formed reacts with the fluorine windows of the infrared cell. The subsequent chemisorption of water gives bands due to CaCl2 hydrates.
Rearrangements in the Diterpenoid Series. Part II. The Diazotization of Methyl 15-β-amino-13-isopropyl-17-noratis-13-en-18-oate
Authors: Ayer William A. , Deshpande Pandurang D.
Published: May 2006

Treatment of methyl 15-β-amino-13-isopropyl-17-noratis-13-en-18-oate (1b) with sodium nitrite – acetic acid gives rise to a variety of products, including nitrated compounds and norketones. The structures of seven of the products have been established. The reaction of methyl 16-isopropylidene-7,17-secoacon-8(15)-en-18-oate (2) with nitrous acid and with dinitrogen tetroxide is described. A simple method for transforming isocyanates to primary amines is presented.
Resolution, Racemization, and Ring Opening of an o,m′-Bridged Biphenyl
Authors: Warnhoff E. W. , Reynolds-Warnhoff P.
Published: May 2006

The ease of racemization and ring cleavage of the dissymmetric o,m′-bridged biphenyl 1 has been examined. Although 1 is structurally stable at least to 100°, it racemizes rapidly in the vicinity of 60°. However, if the nitrogen is converted into a better leaving group by quaternization or protonation, the bridge is quickly broken below 80° by nucleophilic displacement at the benzylic carbon atom. U.v. evidence for strain in 1 is presented.
Five-membered Heterocyclic Thiones. Part III. 1,2,5-Thiadiazole-3-thiones
Authors: Horning D. E. , Muchowski J. M.
Published: May 2006

Stable salts of 3-mercapto-1,2,5-thiadiazoles were prepared by the alkaline hydrolysis of the corresponding N,N-dimethylthionocarbamates.
High Temperature Aqueous Electrolyte Concentration Cells and the Ionization of Liquid Water to 200 °C
Authors: MacDonald Digby D. , Butler P. , Owen D.
Published: May 2006

High temperature aqueous electrolyte concentration cells with and without liquid junction are described. These cells were used to measure the ionization constant of water in 0.1, 0.25,0.5, and]1.0 mol/kg KCl solutions at temperatures to 200 °C. Extrapolation to infinite dilution yielded the following functions for the temperature dependence of log Kw0 and the thermodynamic parameters for ionization: log Kw0 = −4046.16/T + 3.537 − 0.01323T; ΔG0 = 77458.0 − 67.71T + 0.253187T2 J/mol; ΔH0 = 77458.0 − 0.253187T2 J/mol; ΔS0 = 67.71 − 0.5063T J/K mol; ΔCp0 = −0.5063T J/K mol.
Structure of Radicals Produced by γ-Radiolysis. Part 2. Radicals Derived from 5-Membered Alicyclic Molecules
Authors: Linder Ron E. , Ling A. Campbell
Published: May 2006

not available
Transport Numbers for Hydrochloric Acid at Elevated Temperatures
Authors: Macdonald DiGBY D. , Owen D.
Published: May 2006

Transport numbers for H+ and Cl− have been measured as a function of concentration and temperature to 200 °C using electrolyte concentratio cells. The infinite dilution transport number for H+ decreases with temperature while that for Cl− increases. This temperature dependence is discussed in terms of thermal destruction of the three dimensional structure of liquid water.
Evidence for Reactive Intermediates Formed During Pyrolyses of α-Betaines: A Mass Spectrometric Investigation
Authors: Champa Rudolph A. , Fishel D. L.
Published: May 2006

Pyrolytic decomposition of glycine betaine, 2-(N-pyridyl)acetic acid betaine and 2-(N-pyridyl)propionic acid betaine were conducted in inlet systems of two mass spectrometers of differing geometries. Evidence was obtained for primary thermolysis with loss of carbon dioxide to give an ylid from each betaine. The ylids may react further by several alternate pathways involving either hydrogen abstraction, rearrangement and teleomerization, or by divalent carbon transfer by insertion reactions.
The Crystal and Molecular Structure of the Adduct Formed by the Reaction of Tributylphosphine and p-Chlorobenzylidenemalononitrile
Authors: Ferguson George , Fyfe Colin Alan , Marsh Wayne Clifford
Published: May 2006

Crystals of the 1:1 adduct of tributylphosphine with p-chlorobenzylidenemalononitrile are monoclinic, a = 13.719(2), b = 12.557(5), c = 14.229(3) Å, β = 110.59(2)°, Z = 4, space group P21/c. The structure was determined with diffractometer data by direct methods and refined by block-diagonal least-squares calculations to R = 0.10 for 1405 observed reflections. The structure is zwitterionic with the positive charge localized on the phosphorus atom and the negative charge mainly on the terminal —C(CN)2 group.
Processus photophysiques dans la molécule de colchicine
Authors: Roigt H. , Leblanc R. M.
Published: May 2006

The photophysics of colchicine has been studied by absorption and luminescence spectroscopy. The quantum yield of phosphorescence has been found to be 0.86. The quantum yield measurements of colchicine photodegradation in different solvents are reported. The polarity and hydrogen bond character of the solvents are observed to play an important role in these measurements. The Jablonski diagram is proposed for the colchicine molecule.
Terpenes and Terpenoids. IV. Some Esters and Amides of Thujic Acid
Authors: Hach V. , McDonald Elizabeth C.
Published: May 2006

Representatively substituted esters (3c–h) and amides (4a–l) of thujic acid (3a) were prepared using the acid chloride as intermediate and were screened for their insect repellent and attractant potential. N,N-Diethyl thujamide (4d) was found to be a highly active repellent of the yellow fever mosquito (Aedes aegypti) as well as of other insect species.
Reaction of an Aryl Thiocyanate with p-Nitrothiophenoxide Ion and with Thioacetate Ion; Consequences of Nucleophilic Displacement at Sulfur
Authors: Kayser Margaret M. , Gibson Martin S.
Published: May 2006

Reaction of p-acetamidophenyl thiocyanate (Ar1SCN) with p-nitrothiophenol (Ar2SH) in presence of triethylamine gives the diaryl disulfides Ar1SSAr1, Ar1SSAr2, and Ar2SSAr2. Reaction of Ar1SCN with potassium thioacetate gives Ar1SCOMe and Ar1SSAr1. The role of cyanide and arylmercaptide ions in equilibration of disulfides is indicated.
Scope and Limitations of a Cyclization Leading to Phenanthrene Derivatives
Authors: Schmidt C. , Thazhuthaveetil J.
Published: May 2006

The scope and limitations of a modified Bogert–Cook cyclization was investigated. It was found that the sequence is applicable only for the unsubstituted and the meta-substituted series.
Structure cristalline et moléculaire du cyclopentadiényle dicarbonyle dioxyde de soufre manganèse MnC5H5(CO)2SO2
Authors: Barbeau Claude , Dubey Ram Janam
Published: May 2006

The compound MnC5H5(CO)2SO2 crystallizes in the monoclinic system, space group P21/c, in a unit cell of dimensions a = 10.98(2) Å, b = 10.63(2) Å, c = 7.43(2) Å, β = 100.75(8)° with Z = 4. The structure was determined from 1512 reflections obtained on films from a precession camera; the residual factor, R, was 0.093 after a full matrix least-squares refinement. The Mn–S bond seems very strong having a length (2.037(5) Å) which is smaller than the sum of the covalent radii by 0.3 Å The average distance [Formula: see text] is less than that usually observed in manganese–cyclopentadienyl complexes. The two CO groups are distinct. The instability of the complex might be explained, in part, by the crowding of the SO2 and CO ligands. [Journal translation]
A Novel Synthesis of N-Styryl Heterocycles
Authors: Rokach J. , Girard Y. , Atkinson J. G.
Published: May 2006

Reaction of the anions of a variety of 2-carboethoxy N-heterocycles with styrene oxide yields directly the N-(trans-2-styryl)-2-carboxylic acids. The reaction has been shown to proceed through a lactone intermediate which undergoes rapid elimination to form the unsaturated acid. The reaction has been used to alkylate 2-carboethoxy pyrrole, diethyl pyrazole-3,5-dicarboxylate, ethyl indole-2-carboxylate, ethyl benzimidazole-2-carboxylate, and ethyl 2-pyrrolidone-5-carboxylate. Yields were 82, 88, 93.5, 57, and 5% respectively.1-(trans-2-Styryl)benzirnidazole-2-carboxylic acid of m.p. 75–77 °C undergoes an interesting, reversible solid-state transformation to a high melting (255–260 °C), presumably zwitterionic, form.
Lanthanide Shift Reagents in 13C Nuclear Magnetic Resonance: Quantitative Determination of Pseudocontact Shifts and Assignment of 13C Chemical Shifts of Steroids
Authors: ApSimon John W. , Beierbeck Helmut , Saunders John K.
Published: May 2006

The l3C n.m.r. chemical shifts of some monofunctional keto- and hydroxy-steroids were monitored as a function of the concentration of added shift reagent, Pr(fod)3 or Eu(fod)3, and the observed induced shifts were fitted to the geometric quantities in the one-term pseudocontact shielding equation. The correlation between experimental and calculated shifts was quantitative for all carbons except those closest to the complexing site, where contact interactions are most noticeable. With Pr(fod)3 the carbonyl and hydroxyl carbons and the alpha carbons usually had to be excluded from the calculations in order to optimize the correlation between predicted and observed induced shifts for the remaining nuclei and to derive reasonable adduct geometries. With Eu(fod)3, contact shifts were also noticeable at the beta carbons and the europium shift reagents are therefore less useful in 13C n.m.r. spectroscopy. It is shown that the application of shift reagents, in conjunction with off-resonance decoupling, permits the assignment of practically all carbon chemical shifts of the steroids studied.
Smiles Rearrangement in Hydrazonyl Systems: Extension of a Recent 4H-1,3,4-Benzoxadiazine Synthesis
Authors: Elliott Arthur J. , Gibson Martin S. , Kayser Margaret M. , Pawelchak Gordon A.
Published: May 2006

Hydrazonyl aryl ethers derived from hydrazonyl halides Ar1CBr = NNHC6H3XY (2, 4) and (a) o-and p-nitrophenols or (b) pentachlorophenol undergo a facile base-catalyzed Smiles rearrangement to N-aroyl-N′,N′-diarylhydrazines typified by:[Formula: see text]e.g. 6 → 7, 8 → 9, 10 → 11.If the 2-substituent X is Br or F and the 4-substituent Y is electron attracting, the N-aroyl-N′,N′-diaryl-hydrazines can be cyclized under basic conditions to 4-aryl-4H-1,3,4-benzoxadiazines by displacement of X, i.e. 7 → 13, 9 → 14. However, in the analogous cyclization of N′-benzoyl-N′-(2,4-dibromophenyl)-N′-pentachlorophenylhydrazine (11), chlorine rather than bromine is displaced and the migrating ring (Ar2 = C6Cl5) in 10 → 11 becomes the benzene ring of the benzoxadiazine, i.e. 11 → 15.Independent syntheses of two 4-aryl-4H-1,3,4-benzoxadiazines (13a and 14), from 7-bromo-2-phenyl-4H-1,3,4-benzoxadiazine (5a) and o- and p-fluoronitrobenzene respectively, are reported.
Studies on Enaminoketones
Authors: Jirkovsky Ivo
Published: May 2006

A series of N-substituted 3-amino-2-cyclohexen-1-ones and 3-amino-5,5-dimethyl-2-cyclohexen-1-ones (1–9) has been prepared. Halogenation of these compounds with bromine, NBS, cyanogen bromide, and iodine is described. The tendency of enaminoketones to form salts of the corresponding enol-ketimine form was observed and structures of the salts are supported by their p.m.r. and i.r. properties. The reaction of 3-benzylamino-2-bromo-5,5-dimethyl-2-cyclohexen-1-one with concentrated sulfuric acid effected debenzylation. Treatment of 3-benzylamino-2-iodo-5,5-dimethyl-2-cyclohexen-1-one with dibenzoyl peroxide gave 8,8a-dihydro-5-iodo-8,8-dimethyl-2,3-diphenyl-4H-1,4-benzoxazine-6,7-diol. The above secondary enaminoketones 1–9 were shown to react with phenyl isocyanates, phenyl isothiocyanate. and methyl isothiocyanate under fusion conditions to yield substituted 2-amino-6-oxo-1-cyclo-hexene-1-carboxamides and corresponding thiocarboxamides. 2-Benzylamino-6-oxo-N-phenyl-1-cyclohexene-1-carboxamide and its 5,5-dimethyl analog were found to undergo facile transamination in position 2, when heated with a primary amine. This reaction is of synthetic utility for the preparation of biologically active derivatives with a basically substituted side chain. Addition of 4-methylamino-3-pentene-2-one to phenyl isocyanate afforded 2-acetyl-3-methylaminoisocrotonanilide; the spectroscopic properties of this product are discussed.
Reactions of Keten Acetals. Part I. A Simple Synthesis of Some Naturally Occurring Anthraquinones
Authors: Banville Jacques , Grandmaison Jean-Louis , Lang Gérard , Brassard Paul
Published: May 2006

A study of the condensation of keten acetals with some halonaphthoquinones has led to the simple and regiospecific synthesis of some naturally occurring anthraquinones: catenarin, helminthosporin, emodin, and chrysophanol. The results show unambiguously that a previously proposed mechanism is erroneous. The reaction of these acetals with chloromaleic anhydride also provided a one-step preparation of some substituted phthalic anhydrides.
Photocyclization Reactions of Aryl Polyenes. VII. The Photocyclization of 1-Phenyl-4-thienyl- and 1,4-Dithienyl-1,3-butadienes
Authors: Leznoff Clifford C. , Lilie Wolfgang , Manning Carl
Published: May 2006

The photocyclization–oxidation reaction of 1-phenyl-4-(2′-thienyl)-1,3-butadiene gave 4-phenyl-benzo[b]thiophene. Similarly, irradiation of 1-phenyl-4-(3′-thienyl)-l,3-butadiene gave 7-phenylbenzo-[b]thiophene. Thus, photocyclization occurs exclusively to the thiophene ring. Irradiation of 1,4-di(2′-thienyl)-1,3-butadiene and 1,4-di(3′-thienyl)-1,3-butadiene yielded 4-(2′-thienyl)benzo[b]thiophene and 7-(3′-thienyl)benzo[b]thiophene, respectively. Photocyclization of 1-(2′-thienyl)-4-(3″-thienyl)-1,3-butadiene gave an inseparable mixture of 4-(3′-thienyl)benzo[b]thiophene and 7-(2′-thienyl)benzo[b]thiophene.
The Vapor Pressures and Enthalpies of Sublimation of Five Polycyclic Aromatic Hydrocarbons
Authors: Murray John James , Pottie Roswell Francis , Pupp Christian
Published: May 2006

The vapor pressures over benz[a]anthracene (B[a]A), benzo[a]pyrene (B[a]P), benzo[e]pyrene (B[e]P), benzo[ghi]perylene (B[ghi]P), and coronene have been measured using the Knudsen effusion weight loss method. The parameters A and B in the equation log10 [p(atm)] = -(A/T) + B and the enthalpies of sublimation in kcal mol−1 derived therefrom are respectively: B[a]A, 5925 ± 36, 10.045 ± 0.099, 27.12 ± 0.54; B[a]P, 6181 ± 32, 9.601 ± 0.083, 28.29 ± 0.51; B[e]P, 6220 ± 33, 9.736 ± 0.085, 28.46 ± 0.55; B[ghi]P, 6674 ± 40, 9.519 ± 0.093, 30.54 ± 0.55; coronene, 7100 ± 69, 9.110 ± 0.149, 32.49 ± 0.55. The errors shown for the A and B values are standard deviations and for the enthalpies of sublimation are estimates of total probable error.
Orientation in the Wallach Rearrangement for the Naphthyl Azoxy Series
Authors: Dolenko Allan , Buncel Erwin
Published: May 2006

The acid-catalyzed Wallach rearrangement of azoxybenzenes has been extended to the naphthyl azoxy series in order to evaluate the effect of annelation of benzene rings on the course of rearrangement. The six known azoxy derivatives containing the α-naphthyl, β-naphthyl, and phenyl moieties, in various combinations, have been examined with respect to product orientation in moderately strong sulfuric acid solutions. The course of rearrangement (eqs. 2–6) is discussed on the basis of current mechanisms.
Crystal Structure of Bis[hexakis(dimethylamino)cyclotriphosphonitrilium] Tetrachlorocobaltate(II)
Authors: Macdonald Alistair L. , Trotter James
Published: May 2006

Crystals of the title compound, [N3P3(NMe2)6H]2CoCl4, are orthorhombic, a = 34.623, b = 13.964, c = 10.486 Å, Z = 4, space group P212121. The structure was determined by Patterson and electron-density methods and refined by full-matrix least-squares procedures to R = 0.088 for 2178 observed reflexions. Both rings are slightly non-planar, with three distinct pairs of NP bonds: commencing at the protonated nitrogen atom, 1.68, 1.56, and 1.58 Å. The CoCl42− ion is tetrahedral and is hydrogen bonded to both rings, N—H … Cl = 3.32, 3.36 Å.
The Kinetic Activation Volumes for the Binding of Iodide to Cobalamin (Vitamin B12) Studied on a High Pressure Laser Temperature Jump Apparatus
Authors: Hasinoff Brian B.
Published: May 2006

The relaxation kinetics of the reaction of iodide with cobalamin (vitamin B12) were studied on a high pressure laser temperature jump apparatus in aqueous solution at 25° and ionic strength 0.2 M. Analysis of the pressure dependence of the formation and dissociation rate constants gave their respective volumes of activation to be: ΔVf* = 5.50 ± 0.8 cm3 mol−1 and ΔVd* = 11.5 ± 1.6 cm3 mol−1 The positive activation volume for formation of the complex, ΔVf*, after appropriate correction for the volume change due to formation of an outer sphere complex, is consistent with a dissociative type mechanism in which the metal ion – water bond is stretched in the activated complex.
The Conformational Requirements for the Transition State of Bogert–Cook–Bardhan–Sengupta Cyclizations
Authors: Brisse François , Lectard Alain , Schmidt Cirill
Published: May 2006

It is shown that the cyclizations discussed proceed through twist-boat shaped carbonium ions, e.g. 9. Due to structural rigidity such a conformation cannot be assumed in a trans-fused decalin system and the reaction is arrested at the olefinic stage such as 9. The structure of ketoalcohol 9c is elucidated by X-ray crystallography.
The State of Hydrogen Desorbing from Intermediates Formed by Ammonia Interaction with Tungsten Surfaces
Authors: Peng Y. K. , Dawson P. T.
Published: May 2006

Ammonia interaction with a tungsten surface can generate dense adlayers containing nitrogen and hydrogen, i.e. an η-species of surface stoichiometry Ws2N3H. In thermal desorption mass spectrometry experiments, hydrogen desorbing from the η-species interacts with the glass wall in a manner similar to that previously observed for atomic hydrogen. This paper describes two mass spectrometric techniques designed to confirm this conclusion directly. The first method uses a line-of-sight geometry between the tungsten filament and the ionization source of the mass spectrometer and the results indicate that, at least, part of the hydrogen desorbing from the η-species does so atomically. In the second method a multiple wall collision geometry is used but prior saturation of the wall with D atoms will result in an HD+ ion current for desorbing H atoms. The results suggest that 26% of the hydrogen desorbs atomically. Hydrogen atom desorption from the η-species occurs at tungsten filament temperatures below those required for hydrogen atom evaporation from a pure hydrogen adlayer. It is proposed that a reduced binding energy for adsorbed hydrogen atoms and a reduced mobility of these adatoms arises from the presence of a large surface concentration of nitrogen. This will result in the rates of atomic hydrogen desorption and bimolecular recombination becoming comparable at temperatures lower than is the case for pure hydrogen interaction with tungsten. The implications of these results for the ammonia synthesis reaction are discussed.
Juvenile Hormone Analogs in Conifers. II. Isolation, Identification, and Biological Activity of cis-4-[1′(R)-5′-Dimethyl-3′-oxohexyl]-cyclohexane-1-carboxylic Acid and (+)-4(R)-[1′(R)-5′-Dimethyl-3′-oxohexyl]-1-cyclohexene-1-carboxylic Acid from Douglas-fir Wood
Authors: Rogers I. H. , Manville J. F. , Sahota T.
Published: May 2006

The petroleum ether extract from the whole-wood meal of a number of British Columbia Interior-Intermediate variety Douglas-fir trees have yielded two carboxylic acids (+)-todomatuic acid (3b) and cis-dihydrotodomatuic acid (4b) which as their methyl esters are potentially useful juvenile hormone analogs. These compounds possess the R,R and R stereoconfigurations, respectively. The configuration at C-1′ is opposite to that reported by others for "(+)-juvabione" isolated from Abiesbalsamea grown in Czechoslovakia. Whereas (+)-juvabione naturally occurs as and is the methyl ester of (+)-todomatuic acid (4b), in this variety of Douglas-fir these compounds appear as the free acids. Results of biological assays on certain insects indicate that the methyl ester derivatives of these acids are effective ovicides and juvenilizing hormones.
Synthesis of Substituted 9,10-Dihydroanthracenes by the Reduction of Anthraquinones in Hydriodic Acid
Authors: Renaud Roger N. , Stephens J. Campbell
Published: May 2006

Substituted 9,10-dihydroanthracenes were synthesized by reducing the corresponding anthraquinone with a mixture of hydriodic acid, phosphorus, and iodine.
Carbanions in Carbohydrate Chemistry: Approaches to Chemical Precursors of C-Nucleosides
Authors: Hanessian Stephen , Pernet Andre G.
Published: May 2006

The condensation of D-ribofuranosyl halides containing participating (benzoate) and non-participating (benzyl) substituents, with sodio dialkyl malonates and sodio triethyl 1,1,2-ethanetricarboxylate is described. In the presence of participating groups at C-2, the major and sometimes exclusive products were the 1,2-ketal derivatives. Both α- and β-anomeric D-ribofuranosyl malonates were formed in the non-participating series. The possibility of epimerization (anomerization) was experimentally demonstrated.Similar results were obtained with the more highly functionalized tricarbethoxy carbanion. For the participating series however, 20% of C-glycoside was obtained. Condensations with sodio diethyl malonate were also done in the D-arabino series (O-benzyl protecting group) and the anomeric C-glycosyl compounds were isolated and characterized. The mechanistic aspects of these condensations are discussed.
Reaction Kinetics Involving O and N Compounds
Authors: Niki H.
Published: May 2006

Experimental work performed during the past 4 years is reviewed briefly for aeronomically interesting reactions involving ground electronic states of O and N compounds.
A Kinetics Review of Atmospheric Reactions Involving HxOy Compounds
Authors: Davis D. D.
Published: May 2006

Some 49 reactions involving compounds of the type HxOy have been examined in terms of their possible significance to stratospheric and mesospheric chemistry. Of this set of 49, some 20 processes were evaluated to be of potential importance. Within this subset of 20, the rate constants for 8 of these reactions were indicated as either having undergone a significant reevaluation within the last 2 years or were due to be reevaluated based on new data. A discussion of new experimental data resulting in these reevaluations is presented. Finally, recommendations are made as to the need for new experimental work.
Excited State Chemistry in the Stratosphere
Authors: Cvetanović R. J.
Published: May 2006

Potential involvement of excited states of molecules and molecular fragments in the chemistry of the stratosphere is discussed, with particular emphasis on the chemical behavior of electronically excited oxygen atoms.
Isomérisation photosensibilisée par des colorants et photoréduction de l'azobenzène en solution. II
Authors: Ronayette Jacques , Arnaud René , Lemaire Jacques
Published: May 2006

The photochemical isomerization of azobenzene in solution can be sensitized by dyes which have low-lying triplet states (rose Bengal, eosin Y, fluorescein, methylene blue) but cannot be inhibited by such compounds. The two triplet levels, Tβc and Tαc of the cis form are indistinguishable experimentally. On the other hand, the experimental results verify the existence of two triplet levels, Tβt and Tαt, with different properties, in the trans form. Population, by energy transfer, of the lower triplet, Tαt, leads to isomerization with a quantum yield near 0.5, whereas population of the triplet Tβt only rarely leads to isomerization (quantum yield about 0.03).The photoreduction of azobenzene in isopropanol also has been studied. Only the cis form is photoreducible and it is very difficult experimentally to determine whether this photoreduction can be sensitized.A Jablonski diagram of the two forms of azobenzene is presented to correlate these observations. [Journal translation]
Isoméirsation cis–trans de l'azobenzène catalysée par l'iode. III
Authors: Arnaud René , Lemaire Jacques
Published: May 2006

The cis–trans isomerization of azobenzene can be catalyzed by iodine. The rate constant for the reaction of cis-azobenzene with iodine atoms was determined as 2 ± 1 × 106 mol−1 1 s−1, i.e. a much larger value than that pertaining to other isomerizable systems. This very high reactivity of cis-azobenzene allowed the demonstration of surface effects which were unexpected in the liquid phase. A method for estimating low concentrations of iodine atoms can be based on this catalyzed isomerization. [Journal translation]
The Effect of the Excess Kinetic Energy of the O(1D) Atoms from the Flash Photolysis of N2O on their Reaction with N2O
Authors: Wiebe H. Allan , Paraskevopoulos George
Published: May 2006

In order to investigate the suggested involvement of kinetically "hot" O(1D) atoms in their reaction with N2O, O(1D) atoms with a maximum excess kinetic energy in the range 25–47 kcal/g-atom were produced by flash photolysis of N2O in the absence and presence of inert deactivators of kinetic energy such as He and Ne. The following reactions take place:
The Addition of N-Bromoacetamide to 2,3-Unsaturated Nitro Sugars, a New Approach to 2,3-Diamino Sugars. Synthesis of Derivatives of 2,3-Diamino-2,3-dideoxy-D-mannose and -D-talose
Authors: Baer Hans H. , Rank Werner
Published: May 2006

The methyl 4,6-O-benzylidene-2,3-dideoxy-3-nitrohex-2-enopyranosides having the α-D-erythro (1), α-D-threo (10), β-D-erythro (19), and β-D-threo (24) configurations react smoothly with N-bromoacetamide (NBA) in the presence of sodium acetate in acetone or aqueous acetone. The main products are 2-acetamido-3-bromo-2,3-dideoxy-3-nitrohexose derivatives (2, 11, 20, 25, and 26). Depending on the amount of sodium acetate provided, varying proportions of 2-O-acetyl-3-bromo-3-deoxy-3-nitrohexose derivatives (3, 12, and 21) are formed also. The reactions are highly stereoselective in that the acetamido or acetoxy substituent appears to enter exclusively in the position trans to the anomeric methoxyl group. Generally the nitro group in the addition products appears to be oriented equatorially. An exceptional case is the reaction of 24, which gives two C-3 epimers (25 and 26). Borohydride reduction of 3, 12, and 21 results in loss of the bromo and acetoxy substituents leading to known, saturated 2,3-dideoxy-3-nitro derivatives (4, 13, and 23). Compounds 2, 11, 20, 25, and 26 are debrominated by sodium borohydride to give vicinal acetamidonitro derivatives having the following configurations: α-D-manno (5, from 2), β-D-talo (14, from 11), β-D-gluco (22, from 20), and β-D-galacto (27, from 25 and 26). Compound 5 was converted by standard reaction sequences into methyl 2,3-diacetamido-2,3-dideoxy-α-D-mannopyranoside (8) and its 4,6-diacetate 9. Compound 14 was similarly converted into the corresponding derivatives (16 and 17) of hitherto unknown 2,3-diamino-2,3-dideoxy-D-talose.
The Mechanism of the Transition Metal-catalyzed Reaction of 1,1′-Carbonyldipyrazoles with Aldehydes and Ketones
Authors: Peterson L. K. , Kiehlmann E. , Sanger A. R. , Thé K. I.
Published: May 2006

The metal-catalyzed reaction of 1,1′-carbonyldipyrazoles with aldehydes or ketones to give 1,1′-alkylidenedipyrazoles and carbon dioxide, the latter being derived from the amide carbonyl group as shown by labeling experiments, is sensitive to electronic and to steric substituent effects. Under comparable reaction conditions, 1,1′-carbonyldiimidazole, N-acetylpyrazole, and 1-pyrazole-N,N-diethylcarbonamide do not react with acetone while pyrazole-1-carbo(N′-phenylhydrazide) yields an anilino isocyanate dimer. These results are interpreted in terms of a mechanism that involves coordination of the metal ion at the 2,2′-nitrogen atoms of the pyrazole rings and heterolytic cleavage of an amide bond, followed by formation of a carbamate intermediate, decarboxylation, and metal ion exchange. Unsymmetrically substituted 1,1′-carbonyldipyrazoles were found to equilibrate thermally with their respective symmetrical analogs by an intermolecular exchange mechanism.
Charge Development and Mechanism in Disrotatory Ring Opening of Cyclopropyl Bromides
Authors: Ong Jan Han , Robertson Ross Elmore
Published: May 2006

The temperature dependence of the rates of hydrolysis of cis- and trans-2-vinylcyclopropyl bromides has been determined in water. The temperature coefficient of the enthalpy of activation (ΔCp≠) for both compounds was unusual (−27 and −35 cal mol−1 deg−1). From this fact, it was concluded that the charge development at the transition state was low, in agreement with the conclusions of Clark and Smale (19). The slightly inverse α-deuterium isotope effect (kH/kD = 0.994) is consistent with that conclusion.