bluuebunny/crossref_metadata_2025 huggingface dataset:
Aliphatic diazo compounds. XII. The synthesis of 5-endo-hetero-atom-substituted 3-diazo-2-norbornanones and the proton magnetic resonance spectra of these diazo ketones and their precursors
Authors: Yates Peter , Hambly Gordon F.
Published: May 2006

Treatment of 6-endo-acetoxy-5,5-dimethyl-2,3-norbornanedione (6) with tosylhydrazine gives the 2-tosylhydrazone (7), which is converted to 5-endo-acetoxy-3-diazo-6,6-dimethyl-2-norbornanone (1) by basic alumina; the exclusive formation of the 2-tosylhydrazone is ascribed to the smaller steric effect of the endo C-6 acetoxyl relative to the endo C-5 methyl group. The 6-endo-methoxy analogue of 6, 17, and the related 6-endo-chloro- and 6-endo-bromo-1,5,5-trimethyl-2,3-norbornanediones (23 and 26) are similarly converted to the corresponding α-diazo ketones 2–4. The 1H nmr spectra of the diazo ketones 1–4 have their C-1 bridgehead proton signals shifted to higher field relative to the corresponding bridgehead proton signals of the related α-diketones, whereas the C-4 bridgehead proton signals of 1 and 2 are shifted to lower field in relation to the corresponding α-diketone signals. The 1H nmr spectra of the α-diketones show an unusual long range coupling (4J ≥ 1 Hz) between the C-4 bridgehead protons and the exo C-6 protons that is significantly smaller or absent in the spectra of the related diazo ketones and monoketones. In all of these types of compound an endo-methoxyl or -acetoxyl group at C-5(6) shifts the exo and endo C-6(5) methyl signals to lower and higher field, respectively, whereas an endo-halo substituent at C-5(6) shifts both the exo and endo C-6(5) methyl signals to lower field.
Electrochemical studies of the Pb2+/Pb(Hg) system in aqueous and aqueous ethylene glycol solutions
Authors: Rabockai Tibor
Published: May 2006

The electrochemical behavior of the Pb2+/Pb(Hg) system in aqueous and aqueous ethylene glycol solutions is studied in the temperature range of 20.0 to 50.0 °C by means of current reversal chronopotentiometry. It is shown that the reduction of Pb2+ ion is reversible and that kinetic or catalytic complications are not present. The value of dE1/2/dT is −0.6 mV/deg in the aqueous solution and −0.5 mV/deg in the solution with 56% (w/w) or higher concentrations of the organic solvent. In the above concentration range of ethylene glycol the activation energies of diffusion and viscosity vary from 4.3 × 103 to 7.2 × 103 cal mol−1 and from 3.7 × 103 to 6.7 × 103 cal mol−1, respectively. For all solutions the solvodynamic mean radius of the diffusing species remains constant within the experimental error, suggesting that the diffusing species is always the hydrated Pb2+ ion.
Relation entre pression interne et température de fusion. L'entropie volumique de fusion
Authors: Berchiesi Gianfrancesco , Berchiesi Maria A. , Vitali Giovanni , Valenti Venanzio
Published: May 2006

The relation between the internal pressure and the temperature at the melting point is discussed for several organic substances and for some salts.
A facile procedure for the introduction of a hydroxyethyl group. S,S′-Diethyl dithiomalonate as masked ethanol carbanion
Authors: Liu Hsing-Jang , Lai Hoi Kiong
Published: May 2006

A general procedure for the introduction of a hydroxyethyl group has been developed. S,S′-Diethyl dithiomalonate (1) readily undergoes substitution with a variety of electrophiles to give dithiomalonates RR′C(COSEt)2 which on treatment with W-2 Ra-Ni afford ethanol derivatives RR′CHCH2OH.
The correlation between O—H stretching frequencies and hydrogen bond distances in a crystalline sugar monohydrate
Authors: Umemura J. , Birnbaum G. I. , Bundle D. R. , Murphy W. F. , Bernstein H. J. , Mantsch H. H.
Published: May 2006

The Raman and infrared spectra of crystalline methyl 3,6-dideoxy-β-D-ribo-hexopyranoside monohydrate in the O—H stretching region have been studied at room temperature and lower temperatures. Four bands have been identified and correlated with the corresponding O … O distances of the four distinct hydrogen bonds obtained from X-ray data. The assignments were substantiated by a deuterium isotopic dilution study.
Synthesis of 1,3-dihydro-2H-benzo-1,4-diazepin-2-ones and 1,2-dihydropyrazin-2-ones via iminophosphoranes. Mass spectra of 1,5-disubstituted-1,2-dihydropyrazin-2-ones
Authors: Ackrell Jack , Galeazzi Edvige , Muchowski Joseph M. , Tökés Laszolo
Published: May 2006

The azido ketones 4c–e and 10a–d reacted with triphenylphosphine under mild conditions to give the benzo-1,4-diazepin-2-ones 7c–e and the 1,2-dihydropyrazin-2-ones 12a–d, respectively.The electron impact induced fragmentation of the 1,5-disubstituted-1,2-dihydropyrazin-2-ones was shown to occur by extensive skeletal rearrangement. The 1,5-diaryl derivatives 12a–c fragmented via 1,4-diarylimidazole species produced by the expulsion of CO from the molecular ion. In contrast, the 1-cyclohexyl-5-phenyl derivative 12d fragmented almost entirely via a 2-hydroxypyrazine intermediate derived from the molecular ion by McLafferty cleavage.
Phase-transfer catalyzed synthesis of activated cyclopropanes
Authors: McIntosh John M. , Khalil Hamdy
Published: May 2006

not available
Photochemical α-cleavage and hydrogen abstraction in deoxybenzoin: a laser spectroscopy investigation
Authors: Fouassier Jean-Pierre , Merlin André
Published: May 2006

Transient absorptions in the range 380–500 nm in deoxybenzoin are investigated for the first time by nanosecond laser spectroscopy. This study gives evidence for absorption by a triplet state, and by benzoyl and benzyl radicals. Photoreduction of the triplet state and generation of a ketyl radical are also obtained. This enables some peculiar results of the polymerization of vinyl monomers photoinduced by deoxybenzoin to be explained. Our results show that deoxybenzoin exhibits a peculiar behaviour since the two photoprocesses occur with the same efficiency. Hydrogen abstraction and α-cleavage rate constants, quenching rate constants of the species by oxygen, lifetimes of the transients, and absorption spectra are derived. The influence of the solvent is discussed as a function of the excited states involved. A complete diagram of the evolution of the energy levels is thus obtained.
Acid catalysis in the gas phase: dissociative proton transfer to formate and acetate esters
Authors: Hopkinson A. C. , Mackay G. I. , Bohme D. K.
Published: May 2006

The flowing afterglow and selected ion flow tube techniques are employed in gas-phase measurements of the intrinsic kinetics of protonation of methyl formate, n-propyl formate, ethyl acetate, and n-propyl acetate and subsequent fragmentation according to[Formula: see text]with R = H and CH3, R′ = CH3, C2H5, and (CH2)2CH3, and A = H2, CH4, CO, and H2O. Protonation by the acids, AH+, with relative strengths spanning a range of 65 kcal mol−1, is observed to proceed extremely rapidly with rate constants at 299 ± 2 K encompassing values of 2.9 to 8.5 × 10−9 cm3 molecule−1 s−1. Fragmentation is observed for HCOOCH3 only with the strongest acid, H3+, to produce CH3OH2+. For HCOO(CH2)2CH3, fragmentation is observed to produce C3H7+ with H3O+, and also HCOOH2+ with H3+. Little fragmentation of CH3COOC2H5 occurs with H3O+ but with H3+ the major product is CH3COOH2+ with smaller amounts of CH3CO+ and C2H5+. Proton transfer from H3O+ to CH3COO(CH2)2CH3 results in considerable dissociation to form CH3COOH2+. The fragmentation of these esters is discussed in terms of known reaction energetics and in terms of mechanisms for unimolecular acyl–oxygen, AAc1, and alkyl–oxygen, AA11, fission often invoked for analogous reactions in solution as well as modifications of these mechanisms which have been proposed in the context of recent gas-phase measurements.
The synthesis of cyclic peptides by the four component condensation (4 CC)
Authors: Failli Amadeo , Immer Hans , Götz Manfred
Published: May 2006

Since cyclic peptides constitute a group of natural and synthetic products of considerable practical and theoretical significance, model experiments were carried out to explore the scope of the four component condensation for the synthesis of these structures.
The trifluoroacetic acid solvent system. Part VI. Density measurements
Authors: Milne John B.
Published: May 2006

The densities of solutions of several 1:1 trifluoroacetate electrolytes have been measured in 100% trifluoroacetic acid (HOTFA) and apparent molar volumes for their ion pairs have been determined. The density measurements coupled with limiting equivalent conductivities and dissociation constants, calculated by means of the Fuoss–Hsia equation, permit a more precise treatment of the conductivities of solutions at concentrations where the equivalent conductivity minimum occurs. The existence of triple ions in this solvent is not required to account for the conductivity minimum.
Photoreactions of α-sulfonyloxyketones
Authors: Charlton James Leslie , Lai Hoi Kiong , Lypka Gerald Nicholas
Published: May 2006

Earlier work on the photochemistry of α-sulfonyloxyketones uncovered their propensity to form the corresponding α-keto carbonium ions on photolysis. Typical reactions such as intramolecular cyclizations, carbonium ion rearrangements, and solvent trapping were found. This paper describes an attempt to extend this reaction to a general synthetic technique for polyene cyclizations. During the course of this work two other major reaction pathways were found. The first is an α-keto carbonium ion to acylium ion rearrangement and the second is a photoreduction–elimination process that leads to an α-keto radical rather than the corresponding cation.
Aspects of organocadmium chemistry. II. Crystal and molecular structure of a complex between bis(trimethylsilylmethyl)cadmium and 2,2′-bipyridyl
Authors: Bushnell Gordon , Stobart Stephen R.
Published: May 2006

The crystal structure of bipyridylbis(trimethylsilylmethyl)cadmium(II) hemibipyridyl, [Formula: see text] has been solved and refined to an R-value of 0.140 using 1230 reflections. The space group is P21/c and the cell dimensions are a = 887.4(4), b = 947.0(5), c = 3245.(1) pm, β = 92.01(4)°, with four Cd-containing molecules and two bipyridyl molecules of crystallisation per cell. The 4-coordinate geometry at cadmium is most closely related to that of a linear cadmium dialkyl since the angle C—Cd—C = 156(2)°, and the bipyridyl ligand is weakly bound (Cd—N = 252,253 pm) in a symmetrical manner with the angle N—Cd—N = 65(1)°. The distortion from linearity is away from the bipyridyl. The trimethylsilyl groups are also bent back from the heterocyclic ligand and are slightly staggered. The line between the methylene carbon atoms is approximately perpendicular to the mean plane of the bipyridyl molecule.
A reformulation of the theory of unimolecular reactions
Authors: Yau Andrew W. , Pritchard Huw O.
Published: May 2006

not available
Trends in field desorption mass spectra of several series of alkali metal cryptates: thermodynamic rationale and analytical implications
Authors: Wood Gordon Walter , Au Mei-Kuen , Mak Ning , Lau Pui-Yan
Published: May 2006

Field desorption mass spectra have been recorded for most of the 45 cryptates which may be formed from complexation of [2.2.2]-, [2.2.1]-, and [2.1.1]-cryptand with Li+, Na+, an d K+ ions in combination with the anions Cl−, Br−, I−, OTs−, and BPh4−. The cryptate cation predominated in almost all of the spectra. The stability of the complexes was found not to be simply related to goodness of fit of the cation in the cryptand cavity, but a significant trend in stability in the order BPh4 > 1 > Br > Cl was found. This order of complex stability was shown to be consistent with known thermodynamic parameters. These results are discussed briefly in terms of applications to analysis of alkali metal cations.
A total synthesis of (±)-stemarin, a diterpenoid with a unique bicyclic C/D ring System
Authors: Kelly Ronald B. , Harley Mary Lou , Alward Sandra J.
Published: May 2006

A total synthesis of (±)-stemarin, a diterpenoid with a unique C/D ring System, is described. The synthesis features photoaddition of allene to an α,β-unsaturated ketone and two skeletal rearrangements. Application of the synthetic strategy described herein to a synthesis of stemodinol and aphidicolin is anticipated.
An examination of parameters describing the dependance of rate constants on temperature for solvolysis of various organic esters in water and aqueous mixtures
Authors: Blandamer Michael Jesse , Robertson Ross Elmore , William Scott John Marshall
Published: May 2006

The consequences are examined of fitting rate constants and temperatures for a solvolytic reaction to the equation log k = A/T + B log T + C. The coefficients A, B, and C for 150 reactions involving organic derivatives are linearly dependent. Possible mechanistic reasons for this underlying pattern of behaviour are considered. The linearity stems from the least squares analysis used to obtain the coefficients and as a result these quantifies are not truly independent. Consequently, the validity of employing this type of analysis based on the three parameter equation is questioned.
Intramolecular Michael-type additions. II. Synthesis of derivatives of 7-thia-2-azabicyclo[3.2.1]oct-3-ene, a novel heterocyclic ring system
Authors: Baggs Marion E. M , Gregory Brian
Published: May 2006

The isothiouronium salt derived from dimethyl 4-chloromethyl-1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylate reacted with ammonium hydroxide to give dimethyl 7-thia-2-aza-1,3-dimethylbicyclo[3.2.1]oct-3-ene-4,8-dicarboxylate, which could be converted back to a dihydropyridine using iodomethane. Replacement of ammonium hydroxide by sodium hydroxide afforded a tetrahydro- and a dihydrothieno[3,4-c]pyridine as by-products. 3,5-Diacetyl-4-chloromethyl-1,4-dihydro-2,6-dimethylpyridine reacted with thiourea, followed by ammonium hydroxide, to give 3-acetyl-2-methylpyrrole, 4-acetyl- and 4,8-diacetyl-7-thia-2-aza-1,3-dimethylbicyclo[3.2.1]oct-3-ene. The structure and stereochemistry of the novel 7-thia-2-azabicyclo[3.2.1]octenes are established using spectroscopic methods. The mechanism of their formation is discussed in terms of Baldwin's rules.
Oxidative cleavage of conformationally rigid vinyl orthoesters. Evidence for primary and secondary stereoelectronic control in the cleavage of tetrahedral intermediates
Authors: Deslongchamps Pierre , Beaulieu Normand , Chênevert Robert , Dickinson Robert A.
Published: May 2006

Permanganate oxidation of either axial vinyl orthoester 1 or equatorial vinyl orthoester 7 yields essentially hydroxy ester 5 only. These results can be interpreted on the basis of stereoelectronic effects which control the cleavage of tetrahedral intermediates 2 and 8.
Réactions d'addition nucleophiles sur les cétones. Une méthode directe, simple, rapide et précise de mesure de vitesse de formation et de décomposition des combinaisons bisulfitiques
Authors: Boyer Bernard , Lamaty Gérard , Roque Jean Pierre
Published: May 2006

A method is described which allows, with a single experiment, the determination of the rate constants of formation and decomposition of bisulfite addition compounds.
Cinétique d'oxydation des oximes du benzaldéhyde et de l'acétophénone par l'ion thallique
Authors: Lortie Robert , Zador Miklos
Published: May 2006

The kinetics of oxidation of benzaldehyde and acetophenone oximes by Tl(III) in aqueous medium has been studied. The reaction occurs in two consecutive steps: formation of a nitroso intermediate and its decomposition. The oxime forms a complex with Tl(III) leading to the rate equation: −d[oxime]/dt = K1/k2[oxime][Tl(III)]/(1 + K1[Tl(III)]). The formation of the final carbonyl product is inhibited by Tl(III), a resuit of the formation of a complex resistant to decomposition. Coordination of Tl(III) by chloride ions affects the rate of the above two steps. The reaction mechanism is discussed. [Journal translation]
Total synthesis of 3,17β-dihydroxy-6-oxaestra-1,3,5(10),7-tetraen and related miroestrol analogues
Authors: Findlay John A. , Mebe Paul , Stern Michael D. , Givner M. L.
Published: May 2006

3,17β-Dihydroxy-6-oxaestra-1,3,5(10),7-tetraen and related steroidal compounds have been synthesized in high yield via condensation of 7-methoxy-4-vinyl coumarin and 2-methyl-1,3-pentanedione. The approximate uterotrophic activity of the synthetic compounds relative to 17β-estradiol has been determined.
Metal binding to N(9), N(7), and N(3) of adenine. Crystal structure of μ-(adeninato-N3,N7,N9)tris(methylmercury(II)) perchlorate
Authors: Hubert Joseph , Beauchamp André L.
Published: May 2006

The title compound belongs to space group [Formula: see text] with the following cell parameters: a = 6.304, b = 11.925, c = 25.946 Å, α = 85.76, β = 89.78, γ = 83.57°, and Z = 4. The structure was solved by the heavy-atom method and refined on 2570 nonzero reflections to an R factor of 0.044. In the two crystallographically independent [Adeninato(CH3Hg)3]2+ ions, methylmercury groups are linearly bonded to N(3), N(7), and N(9) of a deprotonated adenine ring, forming Hg—N bonds of normal lengths (ave. 2.08 Å) for two-coordinated mercury. One half of the complex cations are associated in a dimeric unit by a pair of strong [Formula: see text] hydrogen bonds, while the others are packed as individual species in the crystal. The structure is stabilized by a number of contacts between mercury and perchlorate oxygens.
Kinetic studies of the reactions of 4-nitrobenzofuroxan with cyanide ion and isopropoxide ion in isopropanol
Authors: Moir Michael E. , Norris Albert R.
Published: May 2006

Kinetic studies of the reactions in isopropanol of 4-nitrobenzofuroxan with cyanide ion and isopropoxide ion have been carried out over the temperature range 15.0 to 35.0 °C. For both bases, the first species identifiable using stopped-flow reaction techniques is postulated to be a C-7 σ-complex of 4-nitrobenzofuroxan and base. Specific rate constants and activation parameters for the formation of these σ-complexes are compared to corresponding data relating to the formation of cyanide ion and isopropoxide ion—σ-complexes of 1,3,5-trinitrobenzene in isopropanol.
Stereochemistry of acid-catalyzed cleavage of 3-chloro- and 3-bromonortricyclene in deuterated medium. Evidence for edge protonation of nortricyclenes
Authors: Werstiuk Nick Henry , Timmins George , Cappelli Frank Peter
Published: May 2006

Cleavage of 3-chloronortricyclene (4c) and 3-bromonortricyclene (4d) occurs faster than solvolysis in D2SO4–DOAc at 70–75 °C and yields syn-7-, anti-7-, exo-5-, and endo-5-halo-exo-2-norbornyl acetates as products. That the 7-chloroacetates comprise 70% of the reaction mixture, that 30% of the 5-chloro-exo-2-norbornyl acetates which comprised 28% of the reaction mixture are derived via rearrangement of the syn-7- and anti-7-chloronorbornyl cations, and that the deuterium at C-6 is at least 90% stereochemically pure endo is evidence that cleavage of the bond farthest removed from the electron withdrawing halogen is preferred 5:1 over the other bonds of the three-membered ring. The Stereochemistry of the ring-opening is rationalized on the basis of cleavage via edge-deuteronation with formation of classical halocations as intermediates. The location of deuterium in the 5-halo-exo-norbornyl acetates is used to define the pathways whereby the 5-haloacetates are formed. This study also establishes that C-6 endo deuterated 7-chloro- and 7-bromo-exo-2-norbornyl brosylates can be synthesized from the corresponding 3-halonortricyclenes.
Mechanism of the formation of quinoline from N-methylacetanilide studied using 13C-labeled substrates
Authors: Leete Edward
Published: May 2006

Pictet discovered 90 years ago that quinoline and p-toluidine were formed on heating N-methylacetanilide with zinc chloride. It has now been shown that 6-methylquinoline is also produced in this reaction. It was established by means of 13C nmr that [1-13C-acetyl]-N-methylacetanilide affords quinoline and its 6-methyl derivative enriched at C-4. [N-methyl-13C]-N-Methylacetanilide yielded [2-13C]quinoline and [2,6-methyl-13C2]-6-methylquinoline. N-Methylpropionanilide afforded 3-methylquinoline. These results are in accord with a new mechanism for the formation of quinoline, different from the one previously proposed.
Photocyclization of aryl halides. Part I. 5-(2-Halogenophenyl)-1,3-diphenylpyrazoles; homolytic fission assisted by radical complexation
Authors: Grimshaw James , Silva A. Prasanna De
Published: May 2006

The photocyclization of 5-(2-halogenophenyl)-1,3-diphenyl pyrazoles proceeds efficiently with the exclusion of solvent participation hydrogen abstraction reactions. In a given solvent, the quantum yields of cyclization [Formula: see text] of Cl, Br, and I compounds show no correlation with carbon–halogen bond dissociation energies. In a series of solvents, [Formula: see text] varies smoothly with solvent viscosity and is independent of solvent polarity. The [Formula: see text] values are independent of triplet quenchers, air, intensity and wavelength of radiation, and reactant concentration. Photocyclization can be triplet sensitized at up to 80% of the direct reaction rate and the reactant triplet energies are about 65 kcalmol−1 while DC—Br is 81 and DC—Cl is 95 kcalmol−1. A mechanism of homolytic fission assisted by radical complexation is proposed to accommodate the results. Photocyclization of the H- and MeO-substituted analogues proceeds inefficiently and with [Formula: see text] values dependent on solvent polarity. An electrocyclic mechanism is followed in these cases. The assisted homolysis model explains several anomalies in the field of aryl halide photochemistry.
A convection-free electrolysis cell in which a steady state is attainable
Authors: Armitage M. Alison , Brydon Gerald A. , Connelly Paul J. J. , Farina Chummer J. E. , Gordon Heather L. , Oldham Keith B. , Yanagi Tadashi
Published: May 2006

Studies of a cell consisting of a sheet of a porous medium soaked with an aqueous electrolyte solution containing the mercurous ion and sandwiched between mercury pools show that steady-state electrolysis may be attained in the absence of convection. Several different porous matrices have been studied and, in some cases, a very simple model of the pore structure predicts behaviour close to that observed experimentally.
The phenolic hydroxyl content of lignin in spruce wood
Authors: Yang J.-M. , Goring D. A-I.
Published: May 2006

Values of the phenolic hydroxyl content of the lignin in the secondary wall and cell corner middle lamella of the tracheids in black spruce wood were found by ultraviolet microscopy to be 0.12 and 0.06 PhOH/C9 respectively. The overall value for the lignin in black spruce wood was 0.10 PhOH/C9.
Total synthesis of tetracyclic sesquiterpenoids: (±)-ishwarone
Authors: Piers Edward , Hall Tse-Wai
Published: May 2006

A stereoselective total synthesis of the racemic modification of the tetracyclic sesquiterpenoid ishwarone (2) is described. Treatment of the known ketal aldehyde 19 with dibromomethylenetriphenylphosphorane gave the dibromo alkene 20, which was transformed efficiently into the propargylic alcohol 21. The latter compound was converted via the intermediates 22–24 into the octalone 12, which in turn was transformed by standard methodology into the corresponding ketal 7. Treatment of 7 with bromoform–aqueous sodium hydroxide in the presence of a phase-transfer catalyst, followed by acid hydrolysis of the resultant crude product, gave the crystalline keto dibromide 27. When a solution of the corresponding ketal 26 in tetrahydrofuran–hexamethyl-phosphoramide containing methyl iodide was treated with tert-butyllithium, the monobromo ketals 28 (58%) and 29 (38%) were formed. Compound 28 was converted by means of conventional reactions into the keto alcohol 32. Attempts to transform the latter substance into (±)-ishwarone (2) proved unsuccessful. When the olefinic ketal 7 was allowed to react with dimethyl diazomalonate in the presence of copper bronze, the diester 44 was produced in good yield. The latter intermediate was converted via standard methodology into the keto dimesylate 47 which, upon reaction with lithium chloride in ether–hexamethylphosphoramide, gave the corresponding dichloride 48. Treatment of 48 with potassium tert-butoxide in tetrahydrofuran resulted in an intramolecular alkylation to provide the tetracyclic keto chloride 50. Reduction of 50 with lithium triethylborohydride in tetrahydrofuran afforded (±)-ishwarol (51) which, upon oxidation with pyridinium chlorochromate in dichloromethane, furnished (±)-ishwarone (2).
The chemistry of thujone. III. Thujone as a chiral synthon for the preparation of sesquiterpenes. Synthesis of (+)-β-cyperone
Authors: Kutney James P. , Balsevich John , Grice Peter
Published: May 2006

Robinson annelation of thujone (1) with methyl and ethyl vinyl ketones proceeds stereospecifically to afford the tricyclic enones 6 and 4 respectively. Enone 4 was converted to the glycol 13 which on treatment with 48% hydrobromic acid gave (+)-9-bromo-β-cyperone (14). Reduction with triphenyltin hydride yielded (+)-β-cyperone (3). Enone 6 was converted via standard means to the cyclopropyl alcohol 9, a potential precursor of (+)-junenol (10).
3-Diethylphosphonoacrolein diethylthioacetal anion (6*), a reagent for the conversion of aldehydes to α,β-unsaturated ketene dithioacetals and three-carbon homologated α,β-unsaturated aldehydes
Authors: Jusr George , Potvin Pierre , Hakimelahi Gholam Hosein
Published: May 2006

A short synthesis of the title compound is reported. It can be used to transform aldehydes to the corresponding α,β-unsaturated ketene dithioacetals, the sulfoxides of which can be converted to α,β-unsaturated aldehydes.
Approaches to some carbohydrate-derived sultones
Authors: Fraser-Reid Bert , Sun King Mo , Tsang Raymond Y-K. , Sinaÿ Pierre , Pietraszkiewicz Marck
Published: May 2006

Under some conditions deprotonation of various mixed disulfonate ester derivatives of carbohydrates leads to intramolecular displacement yielding a product in which a sultone is fused to the sugar ring. The procedure seems to work best when a mesylate and a benzenesulfonate are involved. Examples with both pyranose and furanose sugars are described.
The formation of azoxyalkanes in reactions of some organometallic reagents with N-nitroso-O,N-dialkylhydroxylamines: the nonphotochemical synthesis of an acyclic (E)-azoxyalkane
Authors: Meesters A. C. M. , Rüeger H. , Rajeswari K. , Benn M. H.
Published: May 2006

Azoxyalkanes were found to be regiospecifically formed in the reactions of some alkyllithium and Grignard reagents with N-nitroso-O,N-dialkylhydroxylamines. Remarkably, although (Z)-stereomers were usually produced, in one case the (E)-isomer was predominant.
Regioselective eliminations in reactions of carbohydrate derivatives with superoxide, or with borohydride in 2-propanol
Authors: Rao Vanga S. , Perlin Arthur S.
Published: May 2006

The reaction between 2,3,4,6-tetra-O-benzyl-1,5-di-O-mesyl-D-glucitol (2) and potassium superoxide resulted in the loss of H-4 and the 5-mesyloxy (as well as 1-mesyloxy) substituent, and an almost quantitative conversion into enol ether 4, i.e., 1,3,4,5-tetra-O-benzyl-3-dehydro-2-deoxy-L-threo-hex-2-enitol. When the reaction was performed with 8, in which the 1-O-mesyl group (of 2) is replaced by O-(methoxy)trityl, the outcome was wholly different: an olefin was formed through the removal of a primary (H-6) rather than a secondary (H-4) proton, and nucleophilic displacement also took place. Results similar to those for 8 were obtained with the 2-epimer of 2, i.e., 2,3,4,6-tetra-O-benzyl-1,5-di-O-mesyl-D-mannitol (12). It is suggested that selective displacement of the 1-O-mesyl group of 2 by superoxide generates a 1-peroxy anion (6) that abstracts H-4 intramolecularly, promoting concomitant loss of the 5-mesyloxy group. The transition state for proton abstraction within anion 6 appears to be more stable than that of the corresponding anion in the manno series, accounting for the different reaction routes for 2 and 12. Elimination occurred also in the reduction of 2,3,4,6-tetra-O-benzyl-D-glucopyranose with sodium borohydride in 2-propanol, en route to 2, affording 2,4,6-tri-O-benzyl-2-dehydro-3-deoxy-D-threo-hex-2-enitol (21). The lH nmr spectra of alditol derivatives 2, 8, and 12 show that these molecules depart substantially from extended zigzag conformations, in contrast to configurationally related peracetylated acyclic derivatives.
Betylates. 1. Synthesis and reactions of an isolable [0]betylate, N,N-dimethyl-N-(phenoxysulfonyl)methanaminium fluorosulfate
Authors: King James Frederick , Lee Teresa Mee-Ling
Published: May 2006

Phenyl [0]betylate fluorosulfate (2), the first example of a "[0]betylate" (trialkylammoniosulfate ester), has been prepared by methylation of phenyl N,N-dimethylsulfamate with methyl fluorosulfate. Nucleophiles react with 2 either by attack on the sulfur or methyl carbon atoms, but with no sign of any products derived from benzyne or the phenyl cation. A synthesis of enol N,N-dimethylsulfamates has been devised using a reagent, [Formula: see text], prepared from tetramethylsulfamide and methyl fluorosulfate, but no satisfactory method was found for converting the sulfamic ester to the [0]betylate. Evidence is presented that phenyl chlorosulfate reacts with trimethylamine to give the phenyl [0]betylate which then undergoes further reaction.
Synthesis and stereochemistry of hydrogenated 1,1,4,4,7a-pentamethylindenes
Authors: Thomas A. F. , Ozainne M. , Guntz-Dubini R.
Published: May 2006

not available
Digitoxigenin-3-alkyl ethers
Authors: Greenhouse Robert , Muchowski Joseph M.
Published: May 2006

The synthesis of the title compounds was accomplished by (i) boron trifluoride etherate catalysed alkylation of digitoxigenin with diazoalkanes, (ii) silver tetrafluoroborate assisted solvolysis of 3-desoxy-3α-iododigitoxigen 2d in an alcoholic medium, and (iii) m-chloroperbenzoic acid induced oxidative solvolytic displacement on the iodo compound 2d in the presence of alcohols. The third process was the most useful for the preparation of the mono ethers 2e and 2f of ethylene glycol and glycerol, respectively.
Solvolysis rates in aqueous–organic mixed solvents. IX. Solvolysis of dichloroacetate ion in water–methanol solutions
Authors: Diefallah El-Hussieny M. , Ashy Mohamed A. , Baghlaf Ahmed O.
Published: May 2006

The kinetics of the alkaline solvolysis of dichloroacetate ion in water–methanol solutions have been studied in the temperature range of 50.0 to 65.0 °C and the influence of solvent variation on reaction rate has been examined in terms of changes in the activation parameters. The activation parameters ΔH≠ and ΔS≠ for the solvolysis reaction showed a minimum at about 0.8 water mole fraction. The significance of the results was discussed in view of the electrostatic theory and the changing of solvent structure.
The structure of benzoylphenyldiazomethane
Authors: Cowie Martin , Gauthier Michele D.
Published: May 2006

The structure of benzoylphenyldiazomethane has been established by an X-ray structure determination. The packing of the molecules within the unit cell is related to the complex esr spectral results. Apart from the observed N—N distance of 1.132(5) Å the structural parameters in the molecule suggest conjugation between the diazo and carbonyl functions. The N—N distance is probably anomalously short owing to thermal vibration of the diazo moiety. Benzoylphenyldiazomethane crystallizes in the space group P212121 with a = 5.600(1), b = 13.347(2), c = 15.018(3), and Z = 4. Based on 888 unique observed reflections the structure has been refined to R = 0.052 and Rw = 0.070.
A simple method to characterize feed-coals for liquefaction
Authors: Chakrabartty Sujit K.
Published: May 2006

The analytical techniques for identification of coal-properties relevant to liquefaction processes are not well-developed. A simple method is described to satisfy this need.
Medium effects in protonation equilibrium studies. Accurate acidity constants using the excess acidity method
Authors: Cox Robin A. , Yates Keith
Published: May 2006

Ultraviolet spectra of N-tert-butylbenzamide taken in 0–92% sulfuric acid solutions clearly show that two processes, having roughly equal effects on the spectra, take place over this acidity range. One is protonation of the molecule, and the other is either tautomerization from N- to O-protonated forms, or a pronounced medium effect on the latter. Attempted separation of these two processes using characteristic vector analysis fails. However, separation is possible using an analysis based on the excess acidity (X-function) method. This shows that the second process is a medium effect. The analysis permits accurate calculation of [Formula: see text] and m* values in the presence of medium effects on the acid form, the base form, or both.
A study of aqueous sodium cholate by 2H nmr
Authors: Smith William B. , Barnard Gareth D.
Published: May 2006

Solutions of aqueous sodium 7-2H-cholate have been studied as a function of cholate concentration by 2H nmr. Relaxation times and solution viscosities have been used to show that cholate is monomeric in solution at 0.1 M. Increasing concentration leads to tetramer formation which is complete at 0.1 M. The tetramer solutions are stable up to 55 °C. Solutions of cholate in aqueous pyridine also form tetramers in the same fashion. Evidence was found, however, for a weak hydrogen bonding interaction between the two.
A room-temperature study of the kinetics and energetics for the protonation of ethane
Authors: Mackay G. I. , Schiff H. I. , Bohme D. K.
Published: May 2006

The flowing afterglow and selected-ion flow tube (SIFT) techniques have been applied in room-temperature measurements of the kinetics for proton-transfer reactions of ethane with HeH+, H3+, N2H+, CH5+, N2OH+, and HCO+. The fragmentation of C2H7+ was followed over a range in excess energy of l00 kcal mol−1. Equilibrium constants were measured at low excess energies for the proton-transfer reactions with HCO+ and N2OH+. The latter provided values for the proton affinity of ethane and ΔHf0(C2H7+) and, indirectly, values for the proton affinity of ethylene and ΔHf0 (C2H5+). Additional measurements of the kinetics of the reactions of C2H6 with H+ itself, O+, OH+, and H2O+ provided insight into the competition between proton-transfer and other reaction channels and the fragmentation associated with the C2H6+ ion.
Medium effect. Adsorption of N-methylformamide (NMF) at the Hg electrode from H2O + NMF + NaCl solutions
Authors: Koźmińska D. , Borkowska Z. , Behr B.
Published: May 2006

The adsorption of NMF from H2O + NMF + NaCl solutions has been studied in two series of experiments, one in which µNaCl was kept constant over the whole H2O + NMF composition range and another in which constant concentration of NaCl was maintained. The results are compared and the medium effect discussed.
Etude théorique et vibrationnelle du biphényldicarboximide-2,2′, C14H9NO2. Conjugaison et délocalisation électronique
Authors: Botrel Alain , Caillet Paul
Published: May 2006

Vibrational spectra for 2,2′-diphenyldicarboximide have been determined and allow for a valence force field calculation. Bond orders obtained in this way have been compared with a population analysis and to the bicentric electronic energies determined by a CNDO/2 calculation, thus providing a twofold approach to the electron delocalization in 2,2′-diphehyldicarboxamide. [Journal translation]
Secondary deuterium isotope effects on both rate and product determining steps in the thermolysis of 4-methylene-1-pyrazoline
Authors: Chang Moon Ho , Crawford Robert J.
Published: May 2006

The secondary deuterium kinetic isotope effect in the thermolysis of 4-methylene-1-pyrazoline and four of its deuterated isomers has been studied. The value of δΔG≠/n is 142 cal mol−1 if it is a single C—N cleavage process or 71 cal mol−1 if it is a concerted rupture of two C—N bonds. The product distributions can only be rationalized in terms of a mechanism involving a rate determining C—N bond rupture to form a diazenyl diradical intermediate which then can close to methylenecyclopropanes by three possible modes. This requires a secondary isotope effect in the product determining step of 1.33 ± 0.05, for the rotation of CH2 (CD2) out of the plane of the allylic radical in the intermediate.
Thione photochemistry: on the formation of dipyranylidenes from pyranthiones
Authors: Berenjian Nader , Mayo Paul De
Published: May 2006

The irradiation of the pyranthione 1 has been reinvestigated. The reaction proceeds through the (n,π*) triplet and can be quenched with ferrocene. The reaction can be sensitized with Michler's ketone or triphenylene. The elimination of sulfur from two molecules of 1 to give the dipyranylidene 2 requires, surprisingly, a hydrogen donor solvent, and the quantum yield of product has been found to increase with greater dilution, presumably because of the well-known quenching of triplet thiones by the ground state thione. A mechanism for the formation of 2 is suggested.
The formation and reactions of carbanionic derivatives of methyl phosphazenes
Authors: Gallicano Keith D. , Oakley Richard T. , Paddock Norman L. , Sharma Rajendra D.
Published: May 2006

The cyclic phosphazenes N3P3Ph4Me2, N3P3Me6, and N4P4Me8 are deprotonated by alkyllithiums. The resulting carbanions react with monofunctional electrophiles to form phosphazenes carrying the groups PCH2R (R = Me, Br, I, PhC(O), COOH AsMe2, Me3M (M = Si, Ge, Sn)). Two phosphazenyl groups can be joined either by the use of a difunctional halide or by oxidative coupling of organo-copper derivatives. The formation of the carbanions, the extent of deprotonation, substituent orientation, and the dependence of reactivity on ring size, are interpreted in terms of a balance between π-electron energies and electrostatic interactions.
Attack of H-atoms on aqueous thionine studied by pulse radiolysis
Authors: Solar Sonja , Getoff Nikola , Solar Wolfgang , Mark Franz
Published: May 2006

The reaction mechanism of the H-attack on thionine (TH+) in aqueous solutions (5 × 10−6 to 2 × 10−5 mol dm−3 TH+; 2 × 10−2 mol dm−3t-butanol, pH 1 and 4) was investigated by pulse radiolysis in combination with simulation by computation. Applying a least-squares fitting procedure it was possible to state that at pH 1, 89.5% of the H-atoms react with TH+, k = (8.5 ± 0.3) × 109 dm3 mol−1 s−1, to form semiquinone (•TH32+, λmax = 390 nm, ε390 = 685 ± 20 m2 mol−1; ε720 = 720 m2 mol−1 and λmax = 790 nm, ε790 = 775 ± 20 m2 mol−1), which dismutates to TH+ and leucodye with 2k = (2.4 ± 0.1) × 109 dm3 mol−1 s−1. In addition to this a second H-attack (10.5% H) occurs on the ring carbon of the dye with k = (1.0 ± 0.1) × 109 dm3 mol−1 s−1, resulting in the production of H-adducts. These results are of interest for photogalvanic cells using thionine as a sensitizer.
Aminobenzylation d'aldéhydes phosphoniques: préparation d'acides aminoalkylphosphoniques
Authors: Fabre Geneviève , Collignon Noël , Savignac Philippe
Published: May 2006

The reaction of phosphonic aldehydes with benzylamine in presence of NaBH3CN yields benzylaminoalkylphosphonates which, submitted to catalytic hydrogenation, lead to phosphonic amino esters. When reductive amination is carried out with H2/Pd reduction and debenzylation are observed simultaneously. In the absence of reducing agent the enaminobenzylphosphonate can be isolated and N-alkylated. Hydrolysis of phosphonic amino-esters with dilute HCl gives phosphonic amino acids. The order of occurrence of each operation, as well as the choice of the catalyst is discussed.
Effects of organic solvents on immobilized enzyme catalyses. Chymotrypsin immobilized on porous glass
Authors: Jones J. Bryan , Pliura Diana H.
Published: May 2006

The esterolytic activity of native chymotrypsin (CT) immobilized on ionically neutral porous glass beads has been studied in the presence of up to 20% (v/v) of the organic solvents methanol, ethanol, 2-propanol, tert-butyl alcohol, dioxane, and DMSO. In marked contrast to the variations observed with native CT, inhibition of CT immobilized on glass (CT–glass) was independent of the nature of the organic solvent. The overall activity, as indicated by kc(app)/km(app), decreased by 35–50% as the concentration of all solvents surveyed was increased up to 20%. In general, high organic solvent concentration accelerated the rate of protein release from the insoluble catalyst. For practical applications in aqueous organic solvents CT–glass conjugates are inferior to those of the enzyme attached to Sephadex.
Volume fraction statistics and the surface tensions of non-electrolyte solutions
Authors: Goldsack Douglas E. , Sarvas Carmen Desirrie
Published: May 2006

Explicit and implicit surface tension equations have been derived using both mole fraction and volume fraction statistics and have been applied to a variety of binary polar–polar, non-polar–non-polar, and non-polar–polar organic systems with good success. Average errors of less than 1% are found for a large variety of such systems with the assumption of ideal chemical potential equations and molar surface areas calculated from bulk density values. These equations are found to be valid for those systems with surface tension differences of 20 ergs/cm2 or less. Systems with surface tension differences larger than this value would require the inclusion of activity coefficient effects.
Viscosity of ternary mixtures. IV. Urea – tert-butyl alcohol – water at 25 °C
Authors: Palma Marc , Morel Jean-Pierre
Published: May 2006

We have measured, at 25 °C, the viscosities of urea and tert-butyl alcohol ternary aqueous solutions for total concentrations reaching about 4 M and various ratios of the solutes. We have also determined B coefficients of the Jones–Dole law for urea in water–tert-butyl alcohol mixtures and for tert-butyl alcohol in water–urea mixtures. The results can be fitted in the form:[Formula: see text]where ηr is the viscosity relative to water and subscripts 1 and 2 characterise the two solutes. B1 and B2 are determined in water and the additional D parameters appear as pair-interaction contributions of the solutes to the viscosity of the system. Some relations are established and verified between the previous parameters and the B coefficients of 1 and 2 determined, respectively, in the aqueous mixtures of 2 and 1.
Triphenylphosphine complexes of cadmium(II) perchlorate, nitrate, and trifluoroacetate preparation, characterization, and spectral studies
Authors: Goel Ram G. , Jha Narendra K.
Published: May 2006

1:2 complexes, CdX2(PPh3)2, where X = ClO4, NO3, CF3CO2 and 1:1 complex, Cd(CF3CO2)2PPh3, have been isolated and characterized by elemental analysis and by vibrational and 31P—{lH} nmr spectral measurements. Conductance measurements show that the complexes behave as non-ionic species in dichloromethane. The vibrational spectra of the perchlorato complex are consistent with a six-coordinate structure in the solid state as well as in solution but it is difficult to deduce the structures of the nitrato and trifluoroacetato complexes from the spectral data. Assignments for the metal–ligand stretching frequencies for all the four complexes have been proposed. The 3lP—{1H} nmr spectra of the four complexes have been discussed. Formation of the 1:3 and 1:4 complexes, Cd(ClO4)2(PPh3)3 and Cd(ClO4)2(PPh3)4, in solution, has also been established by 31P—{lH} nmr spectral measurements.
Thermally induced crossed aldol condensations
Authors: Findlay John A. , Desai Dixit N. , Macaulay John B.
Published: May 2006

A relatively efficient, noncatalytic method for effecting crossed aldol condensations between cyclic ketones and aldehydes and between cyclic 1,3-diones and methyl vinyl ketone is reported.
Structure of a trichlorocyclohexenone from bleached kraft chlorination-stage effluent
Authors: McKague A. Bruce , Rettig Steven J. , Trotter James , Douglas George R.
Published: May 2006

Several compounds suspected to be mutagenic have been isolated by large scale fractionation of chlorination-stage effluent from a bleached kraft pulp mill. When reacted with diazomethane, one of these compounds yields a crystalline material, 1. Crystals of 1 are triclinic, a = 7.8814(7), b = 8.3988(8), c = 10.309(1) Å, α = 71.529(8), β = 80.002(7), γ = 62.587(9)°, Z = 2, space group [Formula: see text] The structure was solved by Patterson and Fourier techniques and was refined by full-matrix least-squares procedures to R = 0.030 and Rw = 0.036 for 1795 reflections with I ≥ 3σ(I). The structure analysis has unambiguously identified compound 1 as 1,6-dioxa-4,4,10-trichlorodispiro[2.1.4.3]dodec-10-en-12-one, implying that the material originally present was 1-oxa-6,10,10-trichlorospiro[4.5]dec-6-en-8,9-dione.
The planar conformation of 2-methylthiobenzaldehyde in solution
Authors: Schaefer Ted , Sebastian Rudy
Published: May 2006

The 1H nmr spectral parameters are extracted for a 4 mol% solution of 2-methylthiobenzaldehyde in CCl4 at 305 K. The long-range spin–spin coupling constants involving the aldehydic and methyl protons are consistent only with a preferred conformation in which all heavy atoms are coplanar, as are the chemical shifts of the ring and methyl protons. This conclusion contradicts previous interpretations of the dipole moment, the nmr parameters, and of the infrared data for CCl4 solutions. The present data show that the O-syn and O-anti forms of the compound are present in roughly equal proportions.
The system sulfur dioxide – N-methyl-2-pyrrolidinone
Authors: Adams William A. , Kruus Peeter , Patraboy Timothy J.
Published: May 2006

Solubility and freezing point data are presented for the system sulfur dioxide – N-methyl-2-pyrroIidinone (NMP). The enthalpy and entropy of solution are determined as −33.7 kJ mol−1 and −94.6 J K−1 mol−1, respectively. The freezing point diagram shows maxima at [Formula: see text], suggesting the presence of 2:1 and 1:1 NMP:SO2 complexes. The existence of such complexes in the liquid state is supported by viscosity and permittivity data. Nuclear magnetic resonance and Raman spectroscopic data suggest an overall shift of electron density from the nitrogen and the carbonyl carbon of NMP to the O of SO2, with weakening of the CO bond of NMP.
The synthesis of α-N,N-dimethyl-1′-diphenylphosphinoferrocenylethylamine and related ligands
Authors: Butler Ian R. , Cullen William R.
Published: May 2006

Routes to the title compound were explored based on the cleavage of [1]-ferrocenophanes with aryllithium. Thus the cleavage of [Formula: see text] with phenyllithium affords (η5-C5H4Li)Fe(η5-C5H3(CHMeNMe2)PPh2) and η5-C5H4PPh2)Fe(η5-C5H3Li(CHMeNMe2)) in the ratio 15:85. Hydrolysis of this mixture affords the title compound 4. The lithio-ferrocenes can be treated with XER2 to yield other mixed ligands (E = As, P).A route to 4 via (η5-C5H4PPh2)Fe(η5-C5H4C(O)Me) was also established but it is complicated by low yields and many side products such as [(η5-C5H4PPh2)Fe(η5-C5H4)]2C=CH2.
Total synthesis of the stemodane-type diterpenoids, (±)-2-desoxystemodinone, (+)-2-desoxystemodinone, and (±)-stemodinol
Authors: Kelly Ronald B. , Harley Mary Lou , Alward Sandra J. , Rej Rabindra N. , Gowda Gopala , Mukhopadhyay Asish , Manchand Percy S.
Published: May 2006

Stereospecific total syntheses of (±)-2-desoxystemodinone, (+)-2-desoxystemodinone, and (±)-stemodinol are described. Also described are the isolation of (+)-2-desoxystemodinone from S. maritima and its characterization. A strategy for the elaboration of the C/D ring systems of the stemodane diterpenoids, stemarin and aphidicolin, from a common 6-hydroxybicyclo[2.2.2]octan-2-one system is delineated and its efficacy is demonstrated by the synthesis of the stemodane diterpenoids and our previous synthesis of stemarin.
The cleavage of aryl-metal bonds by elemental fluorine: synthesis of aryl-fluorides
Authors: Adam Michael J. , Berry Joffre M. , Hall Laurance D. , Pate Brian D. , Ruth Thomas J.
Published: May 2006

The reaction of elemental fluorine with phenyl derivatives of tin, lead, germanium, silicon, mercury, and thallium has been studied with the aim of developing a general method for labelling aromatic compounds with radioactive 18F. Rapid synthesis of fluorobenzene was achieved in varying chemical yields up to 70%, depending largely upon the metal substrate used, with aryl–tin compounds giving the highest yields. Radiochemical yields are also given for the synthesis of 18F-fluorobenzene from the cleavage of aryl–tin bonds with 18F-F2.