bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermolysis of the sodium salt of tricarbonyl(acetophenone)chromium p-tosylhydrazone
Authors: Ashraf Muhammad
Published: May 2006

Thermolysis of the sodium salt of tricarbonyl(acetophenone)chromium p-tosylhydrazone was carried out at 116–118 °C in pyridine, both in the presence and absence of 1,1-diphenyl-ethylene and cyclohexene. The products, separated by column chromatography, were shown by analyses to be acetophenone azine, symmetrical and unsymmetrical tricarbonyl(acetophenone azine)chromium complexes, and a diastereomeric mixture of hexacarbonyl(2,3-diphenylbutane)-dichromium and 1-tricarbonyl(phenyl)chromium-1-methyl-2,2-diphenylcyclopropane. The formation of these compounds has been rationalised by the combination of a diazo intermediate and tricarbonyl(methylphenylcarbene)chromium. Their stereochemistry has been discussed in the light of various spectroscopic results.
A total synthesis of myrrhine, (±)-hippodamine, and (±)-convergine
Authors: Ayer William A. , Dawe Robin , Eisner Reinhold A. , Furuichi Kimiaki
Published: May 2006

A seven-step, stereoselective, total synthesis of the ladybug defensive substance myrrhine (5) from 2,4,6-collidine is presented. Successive alkylation and acylation of 2,4,6-collidine followed by ketalization provides 2-(3-[2-(1,3-dioxolanyl)]propyl)-6-(2-methyl-2-[1,3-dioxolanyl]methyl)-4-methylpyridine (14). Sodium–alcohol reduction gives the corresponding all-cis piperidine 17. Hydrolysis of 17 followed by acid-catalyzed cyclization provides ketone 26. Reduction of the carbonyl group in 26 gives myrrhine (5). Cyclization using pyrrolidine – acetic acid gives a mixture of ketones (26 and 31). Reduction of 31 gives (±)-hippodamine (4). Oxidation of (±)-hippodamine with peracid gives (±)-convergine (3).
Etude sur les carbéthoxy-3 pyrazolinones-5: contribution à l'étude des formes tautomériques et préparation de sels d'hydrazinium et de guanidinium
Authors: Zauhar J. , Ladouceur B. F.
Published: May 2006

The tautomeric NH-form is preferentially adopted by 3-carbethoxy-5-pyrazolinones in the solid state and in solution; the solvent does not cause a radical change in form because these molecules are quite polar and appear to be stabilized by a rather extended conjugated system and possibly also by chelation of the carbonyl group of the carbethoxy group in position 3 with the hydrogen atom attached to the nitrogen atom in position 2.These 3-carbethoxy-5-pyrazolinones form hydrazinium and guanidinium salts in the presence of hydrazine and guanidine in ethanolic solution by means of a proton transfer.
Substituent effects of phosphorus and arsenic containing groups in aromatic substitution. VI. Orientation in nitration of some anilides and phenyl esters
Authors: Modro Tomasz A. , Pioch Jerzy
Published: May 2006

The orientation in nitration of N-acyl derivatives of aniline and O-acyl derivatives of phenol in aqueous H2SO4 and in acetic anhydride has been studied. Acetyl and methanesulfonyl derivatives are exclusively ortho/para directing, whereas the N- and O-phosphorylated compounds yield in both media considerable amounts of the meta isomer. The observed differences in orientation are discussed in terms of different protonation sites and strong πp−πd interactions of the oxygen or nitrogen and the P(IV) atom.
The reaction of cis- and trans-1,2-dianisyl-2-phenylvinyl-2-13C bromides with acetic acid and silver acetate
Authors: Lee Choi Chuck , Oka Mitsuo
Published: May 2006

The reaction of cis- or trans-1,2-dianisyl-2-phenylvinyl-2-13C bromide with HOAc–AgOAc gave a 1:1 mixture of cis- and trans-1,2-dianisyl-2-phenylvinyl-2-13C acetates with no isotopic scrambling according to pmr and cmr analyses. The lack of degenerate 1,2-phenyl shift in this system is in contrast with the finding of about 7% scrambling in the analogous reaction with triphenylvinyl-2-13C bromide and mechanistic implications of this difference are discussed.
The influence of manganese(II) and copper(II) on 13C nuclear relaxation rates in imidazole
Authors: Wasylishen Roderick E. , Graham Moira R.
Published: May 2006

13C nuclear relaxation rates have been measured for aqueous solutions of imidazole at 31 °C for several values of pH. The influence of Mn(II) and Cu(II) on these relaxation rates has been examined. The results indicate that 13C transverse relaxation rates of imidazole in the presence of these metals are completely dominated by the scalar mechanism. Because of the important influence of this mechanism it is not possible to obtain the geometry of complexes between imidazole-like ligands and Mn(II) or Cu(II) from 13C line-width measurements.
Behaviour of vanadia-catalyzed SO2 oxidation in the presence of inert, diluent gases
Authors: Rungta Krishna Kumar , Hudgins Robert Ross , Silveston Peter Lewis
Published: May 2006

Observations on the effect of diluent gas on the rate of oxidation of SO2 over a commercial vanadia catalyst reported by Yeramian etal. in a 1970 paper in this journal have been extended in this study.A pronounced increase in rate is observed when inert diluents krypton and C4F8 are substituted for helium. The influence of other diluents was less marked. The increase in rate bas been found to depend upon the partial pressure of the diluent and to be extremely sensitive to the ratios of the reactants.
The acidolysis of p-nitrophenyl sulfate. A kinetic spectrophotometric method for evaluation of pKa
Authors: Buncel Erwin , Chuaqui Claudio
Published: May 2006

A kinetic spectrophotometric method for evaluation of pKa has been developed. In the present study this has been utilized towards the pKa determination, in methanol, of the conjugate acids of 4-picoline, aniline, hydroxylamine, methoxyamine, and hydrazinium ion. For the first two cases the pKa values determined by the present method could be compared with the potentiometrically measured values, in a methanol solvent, with satisfactory agreement. Our proposed method involves essentially the spectrophotometric determination of the rate of the acid catalyzed conversion of p-nitrophenyl sulfate to p-nitrophenol in methanol in the presence of the acidic species whose pKa in this medium is required.
C-Nucleosides and related compounds. VI. Carbocyclic analogues of C-nucleosides: synthesis and derivatives of some useful intermediates
Authors: Just George , Reader Grant , Chalard-Faure Bernadette
Published: May 2006

The Diels–Alder adduct of cyclopentadiene and β-bromo acrylic acid 1 was converted to D,L-exo-6,7-(dihydroxy-di-O-isopropylidene)-2-hydroxy-3-oxabicyclo[3.2.1]octane (9) in an eight-step sequence and a 24% yield based on 1. Alternatively, the hemiacetal 9 was obtained in five steps and 22% yield from norbornadiene through the intermediate lactone 11. The thiosemicarbazone and semicarbazone of 9 were prepared. The synthesis of the free aldehyde 13 as well as that of the Wittig reaction products 12 and 19 are described.
13C nuclear magnetic resonance studies. 58. 13C spectra of a variety of bicyclo[2.2.2]octane derivatives. Further definition of the deshielding δ effect
Authors: Stothers J. B. , Tan C. T.
Published: May 2006

The 13C nmr spectra of 35 bicyclo[2.2.2]octane and -octene derivatives have been determined to extend our examinations of the effects of stereochemistry on the shieldings of closely neighboring carbons. This series includes a variety of methyl substituted bicyclooctanols and -octenols as well as the corresponding hydrocarbons and some bicyclooctanones. With the bicyclo[2.2.2]octane skeleton it is possible to examine an array of systems having substituents separated by three and four bonds in a variety of orientations. The interactions, termed γ and δ effects, respectively, produce distinctive shielding variations which are useful for stereochemical elucidations. Particularly interesting are the pronounced shifts observed for the carbons bearing closely neighboring substituents. Characteristically, for vicinal substituents, these carbons are shielded while for syn-axial δ interactions, these carbons are deshielded by as much as 8.6 ppm. The results are compared with the trends found in other sterically crowded Systems.
On the oxidative dimerization of 2,3-dialkylindoles
Authors: Dave Vinod , Warnhoff E. W.
Published: May 2006

The oxidative dimerization of 3-alkyl-2-methylindoles to 1 has been found to occur with several primary 3-alkyl and one secondary 3-alkyl groups. A tertiary 3-alkyl group prevents dimerization of the intermediate 3-hydroxyindolenine. These new dimers undergo the same acid-catalyzed rearrangement as 1a.
Structure de la mycosporine (P 310)
Authors: Favre-Bonvin Jean , Arpin Noël , Brevard Christian
Published: May 2006

The structure 1 (2-methoxy-3-bis(hydroxymethyl)methylamino-5-hydroxy-5-hydroxymethyl-2-cyclohexen-1-one has been attributed to mycosporine (P. 310), a product isolated from Stereumhirsutum (Willd. ex Fr.) Fr.; this result is derived from the uv, ir, ms, and nmr of 1H and 13C spectral analysis of the natural product and its derivatives.
The structure and equilibria of a manganese(II) complex of fulvic acid studied by ion exchange and nuclear magnetic resonance
Authors: Gamble Donald S. , Langford Cooper H. , Tong James P. K.
Published: May 2006

The binding of Mn2+ to a well characterized fulvic acid sample is reported based on the competition with K+ in an ion exchange equilibration. The free energy of binding of [Formula: see text] to fulvic acid is only 1–2 kJ/equivalent more favourable than that for K+. This suggests an outer sphere electrostatic structure for the complex. The suggestion is confirmed by observation of minimal change in the presence of fulvic acid of the effect of paramagnetic Mn2+ on the nmr spectra of water. The interpretation of nmr spectra is supported by comparison with nmr measurements of Mn2+ complexes with simple ligands and contrast with nmr measurements on Fe3+ – fulvic acid complexing. The latter is confirmed as inner sphere.
The structure of the second coordination sphere of transition metal complexes. V. Nuclear magnetic resonance T1 measurements
Authors: Chan S. O. , Eaton D. R.
Published: May 2006

Proton spin–lattice relaxation times have been measured for several solute and solvent molecules in the presence of paramagnetic chromium(III) acetylacetonate. In each case the T1, values obtained are considerably shorter than those measured in the absence of the paramagnetic complex. Two models are necessary to describe the results. In the first T1 is determined by the diffusional correlation time of the solute molecule. This corresponds to a case in which there is no detectable second coordination sphere and leads to the prediction that T1 will be independent of solute concentration. Acetone, chloroform, and methylene chloride show this behaviour. The second model involves a discrete second coordination sphere and leads to the prediction that above a certain concentration T1 will vary linearly with solute concentration. Methanol shows this behaviour. Calculations show good agreement with the observed T1's for a model with a coordination number of 8, a Cr-to-CH3 separation of 7 Å and an equilibrium constant for displacing solvent (chloroform) of around 10. It is suggested that these results lead to a criterion for second coordination sphere formation compatible with the second coordination sphere requirements for an "interchange" type of ligand exchange mechanism.
Synthesis and radical decomposition of α-hydroxydiazenes. II. tert-Butylazodiphenylcarbinol
Authors: Yeung Dominic W. K. , Warkentin John
Published: May 2006

tert-Butylazodiphenylcarbinol (Ph2C(OH)N=NCMe3, 3) decomposes in oxygen-free benzene by the unimolecular radical mechanism characteristic of most azo compounds. In benzene or in carbon tetrachloride, with or without air present, decomposition of 3 is also induced by radicals through abstraction of hydroxyl hydrogen in concert with the formation of nitrogen. Radicals which induce decomposition of 3 include trichloromethyl, tert-butyl, phenylthiyl, tert-butylperoxy and possibly oxygen. The failure of inhibitors like thiophenol to stop chain decomposition of 3 is interpreted in terms of the thermochemistry of induced decomposition.
The catalytic hydrodesulfurization of thiophenes. VIII. Benzothiophene and 2,3-dihydrobenzothiophene
Authors: Furimsky E. , Amberg C. H.
Published: May 2006

The hydrodesulfurization of benzothiophene (BT) and 2,3-dihydrobenzothiophene (DHBT) has been examined over a commercial cobalt molybdate on alumina and over an unsupported MoS2 catalyst promoted with Co. The results, in particular the appearance of styrene among the products, support cleavage of the hetero-ring in BT as the initial step in the reaction sequence under our low-pressure conditions. Ethylbenzene is the predominant product from both BT and DHBT, although increasingly significant amounts of DHBT are dehydrogenated to BT with rising temperature.
Studies on di-μ-thiocyanato dithiocyanato nickel(II) diisothiocyanato tin(IV) or titanium(IV) and related complexes
Authors: Singh P. P. , Sharma S. B.
Published: May 2006

NiM(NCS)6, [NiL4][M(NCS)6], and [NiL6][M(NCS)6] (M = Sn(IV), Ti(IV); L = pyridine (py), 3-cyanopyridine (cpy), nicotinamide (nia), ethylnicotinate (ent), and ethylenediamine (en)) have been prepared and characterised by elemental analysis, magnetic moment, and infrared and electronic spectral studies. These studies suggest a thiocyanate bridged structure for NiM(NCS)6 and a cationic–anionic structure for [NiL4][M(NCS)6] and [NiL6][M(NCS)6].
Reduction of nitrobenzene with sodium and lithium naphthalenide
Authors: Holy Norman L.
Published: May 2006

Reduction of nitrobenzene with sodium or lithium naphthalenide results in formation of azobenzene and azoxybenzene in modest yields. With sodium naphthalenide, azoxybenzene formation is favored; use of lithium naphthalenide results in enhanced azobenzene yields. Reduction of azoxybenzene with naphthalenide results in azobenzene and a variety of fragmentation products. Hydrazobenzene was the only product formed upon azobenzene formation.
Solvolysis rates in aqueous–organic mixed solvents. III. Kinetics of the alkaline solvolysis of monochloroacetate ion in water – tert-butyl alcohol solutions
Authors: Diefallah El-Hussieny M.
Published: May 2006

The temperature dependence of the rate of alkaline solvolysis of monochloroacetate ion in water – tert-bulyl alcohol solutions has been determined. The rates of reaction were first order with respect to both the chloroacetate ion and to the total solvoxide ion concentrations. The reactivity is enhanced, first slowly, and then more rapidly, by increasing the concentration of tert-bulyl alcohol in the solvent mixtures. The rate of reaction increases with the reciprocal of the dielectric constant of the medium and the plot of log kvs. 1/D can best be represented by two lines intersecting at a point corresponding to 0.9 water mole fraction. The activation parameters ΔH*and ΔS* for the solvolysis reaction showed a minimum at about 0.9 water mole fraction. The significance of these results from the viewpoint of the electrostatic theory and the changing of solvent structure in such mixtures is discussed.
The collisional quenching of electronically excited oxygen atoms, O(21D2), by the gases NH3, H2O2, C2H6, C3H8, and C(CH3)4, using time-resolved attenuation of atomic resonance radiation
Authors: Fletcher I. S. , Husain D.
Published: May 2006

A kinetic study of electronically excited oxygen atoms, O(21D2), is presented. These optically metastable species were generated by repetitive pulsed irradiation in the Hartley-band continuum and monitored photoelectrically in absorption by time-resolved attenuation of resonance radiation at λ = 115.2 nm (O(31D20)←O(21D2). Absolute rate constants for the collisional quenching of O(21D2) are reported for the gases NH3, H2O2, C2H6 C3H8, and C(CH3)4. These are found to be respectively (in units of 10−10 cm3 molecule−1 S−1 at 300 K), 6.3 ± 0.7, 5.2 ± 0.6, 7.3 ± 0.8, 9.5 ± 1.0, and 12.3 ± 1.3. With the exception of a recent measurement for NH3• these data represent the first absolute measurements for these quenching gases. Further, a general comparison is made between absolute rate measurements using this technique and recent work by Schiff and co-workers using time-resolved emission at λ = 630 nm (O(21D2) → O(23P2)) in order to monitor the excited atoms.
A study of molecular motion in tetramethylphosphonium halides by proton magnetic resonance
Authors: Ang T. T. , Dunell B. A.
Published: May 2006

Spin–lattice relaxation times of tetramethylphosphonium chloride, bromide, and iodide were measured between 100 and 500 K and the two minima in T1 found for each compound have been assigned to methyl group reorientation and whole cation tumbling. The second moments also indicate that the cations are tumbling isotropically at nmr frequencies in the upper half of this temperature range, and suggest that librational oscillation of the whole cation occurs at frequencies at least of the order of 105 s−1 near 150 K. The energy barriers for both methyl group reorientation and isotropic tumbling decrease from chloride to bromide but increase when one goes from bromide to iodide. Powder photograph X-ray diffraction analysis indicates that the chloride and bromide have hexagonal crystal structures (a and c measured), but that the iodide has lower, undetermined symmetry.
Reaction of organic compounds under high temperature – dilute acid (HTDA) conditions. II. The hydration–exchange of norbornadiene and benzonorbornadiene in aqueous acetic acid at 250 °C
Authors: Werstiuk Nick Henry , Kadai Tonu
Published: May 2006

The hydration of norbornadiene (1) under the HTDA conditions of aqueous acetic acid at 250 °C gives via norbornanediols and norbornenols as intermediates, the sink-product aldehydes 3, 4, 5, and norcamphor (6). When the reaction is carried out in deuterated medium on the average, 2.5 atoms of deuterium are incorporated into each of the products. Hydration of benzonorbornadiene (2) at 250 °C gives the alcohols 40 and 41 and the acetates 42a and 42b as products. When the hydration is carried out in deuterated medium, while only one atom of deuterium is incorporated into the [2.2.1]-framework, exchange of the aromatic moiety proceeds to completion.
A proton magnetic resonance estimate of the extent of intramolucular hydrogen bonding in derivatives of 2-trifluoromethyl phenol. Solvent effects
Authors: Schaefer Ted , Rowbotham J. Brian
Published: May 2006

The long-range spin–spin coupling constants between hydroxyl protons and ring protons or fluorine nuclei are used to establish the conformer populations in iodine and brornine derivatives of 2-trifluoromethylphenol in C6H12, CCl4, and C6D6 solutions. The sequence Cl, [Formula: see text] is established for the so-called hydrogen bonding preferences of the hydroxyl group in 2,4,6-trisubstituted phenols, the corresponding free energy sequence being −ΔG = 1690, 1690 > 1300 > 1230 > 0 ± 200 cal/mol at 32 °C in CCl4 solution. An indirect estimate of the free energy differences in the vapor phase suggests the sequence −ΔG = 2800, 2800 > 2400 > 2300 > 1100 ± 300 cal/mol; the latter value meaning that the hydroxyl group in 4-bromo-2-trifluoromethylphenol prefers the CF3 group by this amount in the vapor phase. Benzene interacts preferentially with the OH group in this compound to the extent of 1300 cal/mol (ΔG), referenced to the vapor phase.
The stereochemistry of 1,3,5-trimethyl-4-piperidone and its 4-phenylalcohol derivatives
Authors: Hanisch P. , Jones Alan J.
Published: May 2006

The configurations in solution of the three diastereoisomeric alcohols obtained from the reaction of phenyllithium on 1,3,5-trimethyl-4-phenylpiperidone have been determined unequivocally using 13C and 1H magnetic resonance methods.
The crystal structure of the complex salt imidazole imidazolium perchlorate
Authors: Quick Andrew , Williams David J.
Published: May 2006

The crystal structure of imidazole imidazolium perchlorate has been determined at room temperature from three-dimensional diffractometer data, and refined by full-matrix least-squares to a final R = 0.051. The planar imidazole rings are linked by a [Formula: see text] hydrogen bond of length 2.73 Å and rotated with respect to each other about this bond by an angle of 50°. The analysis has failed to give conclusive evidence as to the position of the hydrogen atom between the two imidazoles.
Evidence for one-bond cleavage in the thermolysis of (−)-(S)-1-diphenylmethyl-2-(2-butyl)diazene and of 1-diphenylmethyl-2-phenyldiazene
Authors: Kopecky Karl R. , Pope Peter M. , Sastre Juan A.Lopez
Published: May 2006

Thermolysis of (−)-(S)-1-diphenylmethyl-2-(2-butyl)diazene (−)-(S)-1 at 100 °C in benzene and in benzene containing 1 M butanethiol produces (−)-(R)-1,1-diphenyl-2-methylbutane (−)-(R)-6 with 2 and 6% net inversion of configuration, respectively. These results indicate that the rate determining step is a one-bond cleavage to give diphenylmethyl and 2-butyldiazenyl radicals because a two-bond cleavage process cannot produce a coupling product with net inversion of configuration. The cage effect is at least 13% on thermolysis of (±)-1 at 100 °C in benzene containing 1 M butanethiol. (−)-(R)-6 is not thought to be formed by a displacement reaction of the diphenylmethyl radical on the (S)-2-butyldiazenyl radical. An estimate for the lifetime of the latter radical is ∼10−10 s or less. There is a small viscosity effect on the rate of thermolysis, k, of (±)-1. At 77.6 °C in cumene, octane, and hexadecane k = 4.48, 4.28, and 3.95 × 10−5 s−1, respectively. At 77.6 °C in cumene ΔH≠ = 30.5 ± 1.3 kcal/mol and ΔS≠ = 8.1 ± 4.0 eu for thermolysis of (±)-1.No emission or enhanced absorption due to the methine proton of the diphenylmethyl group of (±)-1 was detected in the nmr spectrum of the thermolysis at 120 °C in hexadecane.Enhanced absorption of the corresponding proton was observed in the nmr spectrum of thermolysis in hexadecane of 1-diphenylmethyl-2-phenyldiazene 7 at 180 °C which indicates one-bond cleavage occurs in this system. No evidence for the formation of crossed azo products was obtained when concentrated solutions of 7 and its tri-p-tert-butyl derivative were thermolized for one half-life (25 s) at 190 °C. This indicates that the phenyldiazenyl radical does not survive long enough to encounter a diphenylmethyl radical produced from another molecule of azo compound.
Crystallographic studies on neuroleptics of the benzocycloheptapyridoisoquinoline series. The crystal structure of butaclamol hydrobromide and the absolute configuration and crystal structure of dexclamol hydrobromide
Authors: Bird P. H. , Bruderlein F. T. , Humber L. G.
Published: May 2006

The compound butaclamol hydrobromide crystallizes in space group P21/c with cell dimensions; a = 14.38(3), b = 13.31(3), c = 12.07(3) Å, β = 101.64(8)°. The structure was solved by Patterson methods and non-hydrogen atoms have been refined isotropically using a full-matrix least-squares to an R value of 0.17 for 779 observed reflections.The compound dexclamol hydrobromide crystallizes in space group P212121 with a = 8.412(2), b = 24.392(7), c = 10.465(2) Å. Refinement of non-hydrogen atoms using isotropic thermal parameters and rigid aromatic rings converted at R = 0.090 using 1249 observed reflections, for the preferred enantiomorph, and R = 0.099 for the other enantiomorph.Both compounds have their hydroxy groups in the axial position, and both adopt conformations of the seven membered ring such that the C13b hydrogen atom experiences a flagpolebowsprit interaction with a hydrogen atom of C9.
Alcoxy-2, aryloxy-2, acyloxy-2 cyclohexanones. Synthèse et étude de leur équilibre conformationnel
Authors: Cantacuzene D. , Tordeux M.
Published: May 2006

We show a linear Hammett correlation in the conformational equilibrium of 2-aryloxycyclohexanones when the X substituent located para on the phenyl ring is electron withdrawing. This leads to the prediction of the equatorial position of the substituent in the 2-acyloxycyclohexanones. The conformational equilibria of 2-alcoxycyclohexanones (R = CH3 to C(CH3)3) also are examined.
Nematic phase nuclear magnetic resonance studies of the structure and orientation of 1,5- and 2,6-naphthyridines
Authors: Lee Y. P. , Gilson D. F. R.
Published: May 2006

The proton magnetic resonance spectra of 1,5- and 2,6-naphthyridine dissolved in the nematic liquid crystal MBBA have been analysed. The proton geometries do not give good fits to the ring skeleton structure but it appears that the carbon–hydrogen bond lengths are not all of equal length and the bond angles indicate some bending of the C—H bonds toward the adjacent nitrogen atom. The probability functions for orientation of diazanaphthalenes in nematic solvents show that nitrogen atoms in the ring framework affect the direction of principal orientation, which does not follow either the maximum molecular dimension or the inertial axis.
8-Oxo-8H-1,2,4,-oxadiazolo[2,3-i]purines
Authors: Devlin John P.
Published: May 2006

The preparation of 8-oxo-8H-1,2,4-oxadiazolo[2,3-i]purines (1) and their mass spectral fragmentation patterns are described. Novel imidazol-5-yl-4H-1,2,4-oxadiazol-5-ones (5) are formed upon acid hydrolysis of 1.
Polybrominated derivatives of 5α-androstane and 5α-estrane 3-ketones: cyclopropanol formation
Authors: Templeton J. F. , Wie C. W. , Hruska F. E.
Published: May 2006

Bromohydrin acetates from sodium borohydride reduction of di- and tribrominated 17β-hydroxy-5α-androstan-3-one and 17β-hydroxy-5α-estran-3-one have been prepared and their structures determined by spectroscopic methods. Some 220 MHz proton magnetic resonance data are reported for structure determination. The formation of cyclosteroid derivatives by 1,3-elimination of bromine with zinc–copper couple is discussed.
Etude des phénomènes de redistribution des groupements monofonctionnels -R, -F, -Cl, -Br, -I, -SCN sur des atomes de bore tricoordonnés
Authors: Costes Jean-Pierre , Cros Gerard , Laurent Jean-Pierre
Published: May 2006

A study by 11B and 1H nmr of the scrambling reactions between the boron trihalides BX3 (X = I, Br, Cl, F) and the trialkylborane BR3 (R = C3H7, C4H9) shows that the mixed species, on equilibrium are non uniformly favoured. The effects of Lewis acidity and steric hindrance are discussed.
The crystal and molecular structure of thiamine iodide hydroiodide
Authors: Lee William Edward , Richardson Mary Frances
Published: May 2006

The X-ray crystal structure of thiamine iodide hydroiodide, C12H18N4OSI2, has been determined. The unit cell parameters are: a = 13.835(7), b = 7.442(4), c = 20.243(9) Å, β = 120.52(7)°, monoclinic space group P21/c, Z = 4. A total of 1445 reflections having F2 > 2σ(F2), 2θ < 40° were collected on a Picker 4-circle diffractometer with MoKα radiation by the 2θ scan technique. The structure was solved by the heavy-atom method. The iodide and sulphur atoms were refined anisotropically; only positional parameters were refined for the hydrogen atoms. Successive full-matrix least-squares refinements yielded an unweighted R-factor of 0.054. The pyrimidine ring is protonated on the ring nitrogen opposite the amino group. The relative disposition of the pyrimidine and thiazolium rings is similar to that observed in most other thiamine structures. The β-hydroxyethyl side chain of the thiazolium ring is folded in such a way that there is a short S … O contact, 2.97 Å in length. The iodide ions are involved in a number of weak hydrogen bonds.
The addition of 4-chlorobenzenesulfenyl chloride to phenyl-substituted acetylenes: the structures of the intermediate thiirenium ion
Authors: Schmid George H. , Modro Agnieszka , Garratt Dennis G. , Yates Keith
Published: May 2006

A comparison is made of the effect on the rates and product compositions of substituting a phenyl ring for a hydrogen on ethylene and acetylene and their derivatives. Such a comparison leads to the conclusion that the structure of the intermediate phenyl thiirenium ion, formed by the addition of an arenesulfenyl chloride to phenylacetylenes, is one in which charge is delocalized into the phenyl ring.
Oxidative cleavage of tertiary cyclobutanols. A new synthetic approach to 1,4-ketols and 1,4-diketones
Authors: Liu Hsing-Jang
Published: May 2006

The reaction of tertiary cyclobutanols with Jones reagent under mild conditions resulted in the oxidative cleavage of the cyclobutane ring to give, depending on the substitution pattern of the starting alcohol, a 1,4-ketol or a 1,4-diketone.
Kinetic and spectrophotometric studies of binding of iron(III) by glutathione
Authors: Khan Tahir R. , Langford Cooper H.
Published: May 2006

In this report, determination of unbound aquo iron species is accomplished by a kinetic method involving reaction with sulfosalicylic acid (SSA) on a time scale which is very short with respect to reaction of SSA with the glutathione complexes of iron. The data are used to calculate conditional binding constants for Fe(III) to glutathione. Binding constants in 0.1 M ionic strength media were obtained between pH 1 and 2.4 by the kinetic method, and near pH = 3 by spectrophotometry and by examination of the ratio of rate of complex formation and dissociation. The conditional binding 'constant' between pH 1 and 3 is represented as pK = −1.96 – 0.50pH. This is consistent with the importance of reactions involving only very limited proton release. Spectrophotometric data show that the —OH group on Fe(OH)2+ is lost on glutathione complexing. Kinetics of the complex formation reaction between aquo iron(III) species and glutathione are slower than rates of reaction of iron(III) with simple ligands.The glutathione system is regarded as a model system important to natural water chemistry because it is a widely distributed biological sulfur-containing chelating agent.
Electrochimie de composés organométalliques. II. Nouvelle voie d'accès aux sels de cobalticinium substitués
Authors: Murr Nabil El , Laviron Etienne
Published: May 2006

The oxidation of several substituted cyclopentadiene cobalt cyclopentadienyls electrochemically, by air, by hydrogen ions, and by triphenylmethyl tetrafluoroborate has been studied. The derivatives with an exo hydrogen yield the corresponding cobalticinium salts. When the exo substituent is CH3 or C6H5, a degradation occurs. If the exo substituent is CO2CH3, oxidation by triphenylmethyl tetrafluoroborate takes place with endo hydrogen elimination, leading to the substituted cobalticinium salt in quantitative yield.
Nuclear magnetic resonance studies of the acid–base chemistry of amino acids and peptides. III. Determination of the microscopic and macroscopic acid dissociation constants of α,ω-diaminocarboxylic acids
Authors: Sayer Thomas L. , Rabenstein Dallas L.
Published: May 2006

The acid–base chemistry of 2,3-diaminopropionic acid (dap), 2,4-diaminobutyric acid (dab), ornithine (orn), and lysine (lys) has been studied by 13C and proton nmr spectroscopy. Macroscopic acid dissociation constants for titration of the two ammonium groups of each molecule have been calculated from the 13C chemical shift titration curves for the alkyl carbon atoms by nonlinear least squares curve fitting methods. Microscopic acid dissociation constants for the simultaneous titration of the two ammonium groups of protonated orn and lys have been obtained from their proton chemical shift titration curves and from the 13C titration curves for orn and dap. The results indicate that the α-ammonium group of each of these α,ω-diaminocarboxylic acids is more acidic than its ω-ammonium group, but that the difference decreases as the number of carbons separating the ammonium groups decreases so that the acidities of the two ammonium groups of dap are almost identical. Results of pmr studies of the acid–base chemistry of glycyl-L-lysine and L-lysylglycine also are reported.
The basicity of aliphatic carboxylic acids
Authors: Lee Donald G. , Sadar M. H.
Published: May 2006

The basicities of four aliphatic carboxylic acids (propionic, isovaleric, 3-chloropropionic, and 3-fluoropropionic) have been investigated using nmr chemical shift data. The results indicate that the protonation behaviour of the unsubstituted and the halogen substituted compounds are not defined by the same acidity function.
Etude du mécanisme de la formation de phosphates d'énols à partir de composés carbonyles &([a-z]+);-halogénés et de trialcoylphosphites
Authors: Gaydou Emile M. , Bianchini Jean-Pierre
Published: May 2006

Kinetic studies of the reactions of meta- and para- substituted ω-chloro- and ω-bromoacetophenones with various trialkylphosphites were done in order to elucidate the mechanism for the formation of the corresponding enols. Values were determined for the energies and entropies of activation as well as for the Hammett ρ constants. The mechanism of the reaction is discussed taking into account also the stereochemistry of the products obtained in the case of aldehydes and of variously substituted α-halogenated methylketones. [Journal translation]
Reduction of sulfates by hydrogen
Authors: Habashi Fathi , Mikhail Shaheer A. , Van Kim Vo
Published: May 2006

The initial stage of reduction of anhydrous sulfates by H2 may lead to the formation of any of the following: (1) sulfates at lower valency, e.g., reduction of CuSO4, HgSO4, Fe2(SO4)3; (2) metals, e.g., Cu2SO4, Ag2SO4; (3) sulfides, e.g., NiSO4, CoSO4, CdSO4, CaSO4, SrSO4, BaSO4, and alkaline metal sulfates; (4) oxides, e.g., Al2(SO4)3, MgSO4, BeSO4; (5) a mixture of oxide and sulfide, e.g., FeSO4, MnSO4, ZnSO4, PbSO4. While CuSO4, Ag2SO4, and PbSO4 are the only sulfates that yield metals on reduction, CuSO4 is the most interesting because it yields the metal at 350 °C. PbSO4 is reduced to metal at about 800 °C, and Ag2SO4 already yields the metal by thermal decomposition above 800 °C.
Chemical and biological studies on 1,2-dihydro-s-triazines. XIX. A nuclear magnetic resonance investigation of hindered internal rotation in 1-aryl derivatives
Authors: Colebrook Lawrence D. , Giles H. Gwynne , Rosowsky Andre , Bentz Wesley E. , Fehlner James R.
Published: May 2006

Substantial barriers to internal rotation about aryl C—N bonds have been detected by pmr methods in a series of 2-methyl- and 2,2-dimethyl-substituted 4,6-diamino-1-aryl-1,2-dihydro-s-triazines. In most of the 2,2-dimethyl compounds the barriers are too high to be measured by the pmr lineshape method. When the blocking groups on the aryl moieties are large the barriers may be measured in the 2-methyl series by following the equilibration of diastereomeric rotamers. When the blocking groups on the hetero rings are sufficiently small, rate constants may be measured by pmr lineshape analysis. A substantial barrier to rotation has been measured in the absence of bulky blocking groups on the aryl ring.
The synthesis of spiro[bicyclo[2.2.1]heptene-7,1′-cycloalkan]-2′-ones and related benzobicyclo[2.2.1]heptene derivatives
Authors: Feiner N. F. , Abrams G. D. , Yates Peter
Published: May 2006

7-Norbornenone gives on treatment with diphenylsulfonium cyclopropylide an epoxide that rearranges thermally to a mixture of syn- and anti-spiro[bicyclo[2.2.1]heptene-7,1′-cyclobutan]-2′-ones. Treatment of 7-norbornenone with cyclobutylidenetriphenylphosphorane gives 7-cyclobutylidenenorbornene, which on epoxidation and rearrangement gives syn-spiro[bicyclo[2.2.1]heptene-7,1′-cyclopentan]-2′-one. This is also formed on treatment of syn-spiro[bicyclo[2.2.1]heptene-7,1′-cyclobutan]-2′-one with tert-butyl diazoacetate and triethyloxonium fluoborate followed by decarboalkoxylation. Similar homologation of anti-spiro[bicyclo[2.2.1]-heptene-7,1′-cyclobutan]-2′-one affords anti-spiro[bicyclo[2.2.1]heptene-7,1′-cyclopentan]-2′-one. 7-Isopropylidenebenzonorbornene with acetyl chloride and aluminum chloride gives 7-syn-acetyl-7-anti-isopropenylbenzonorbornene, which on dibromination followed by condensation with isopropylidene malonate gives a dispiro ketone related to these spiro ketones. The structures of the spiro compounds have been established by infrared and nuclear magnetic resonance spectroscopy and by studies of their reactions.
Chemistry of metal hydrides. Part XIX. Stereochemical changes at platinum during the insertion of acetylenes with platinum(II) hydrides
Authors: Clark H. C. , Fiess P. L. , Wong C. S.
Published: May 2006

The reactions of trans-[PtH(PEt3)2(acetone)]+ and trans-[PtH(PEt3)2(CO)]+ with a variety of acetylenes are described. The geometries of the products with respect to the platinum centre and to the stereochemistry of the alkenyl group have been determined on the basis of their 1H nmr parameters. For reactions with the cation containing acetone, and particularly from a variable temperature 1H nmr study of its reaction with 2-butyne in the presence of water, the insertion pathway is shown to be entirely analogous to that for olefin insertion, involving an initial displacement of the trans ligand by acetylene, isomerization to a cis-like intermediate, migratory insertion rearrangement, and re-combination with an appropriate ligand to give either cis or trans platinum products. The insertion pathway with the carbonyl cation is dependent on the nature of the acetylene; for non-activated or weakly activated acetylenes insertion occurs via five-coordinate intermediates, but with strongly activated acetylenes, the same mechanism as with the acetone cation appears to occur, involving reversible loss of carbon monoxide.
Charge distribution in dioxygen complexes of cobalt(III). The crystal structure and absolute configuration of (+)546-Δ-cis-β-[{2,13-dimethyl-6,9-diphenyl-2,6,9,13-tetraarsatetradecane}(dioxygen)cobalt(III)] perchlorate
Authors: Crump David B. , Stepaniak Robert F. , Payne Nicholas C.
Published: May 2006

The crystal structure and absolute configuration of an optically active dioxygen complex of cobalt(III) have been determined from three dimensional X-ray diffraction data collected by counter techniques. (+)546-Δ-cis-β-[Co{R,R-(CH3)2As(CH2)3As(C6H5)(CH2)2As(C6H5)(CH2)3As(CH3)2}O2]ClO4 crystallizes in the orthorhombic space group P212121, in a unit cell of dimensions a = 12.595(7), b = 20.937(10), and c = 11.509(6) Å. There are four formula units per cell. The structure was refined on F by full matrix least-squares techniques, and converged with an agreement factor R = 0.0474 based on 2988 independent observations collected from two crystals. The absolute configuration of the cation was determined by the Bijvoet absorption edge technique to be Δ. The tetradentate ligand adopts the cis-β configuration around the cobalt atom. One six-membered ring has a chair conformation; the other is disordered, and occurs with equal probability in a chair and a distorted boat conformation. The five-membered chelate ring has a gauche conformation, of absolute configuration λ. The absolute configurations at the asymmetric arsenic atoms are both R. The O—O bond length is 1.424(10) Å. The assignment of formal oxidation states to the cobalt atom and the dioxygen ligand is discussed in light of the molecular geometry and the optical properties of the cation.
Acetyl group relaxation in four aromatic ketones
Authors: McLellan C. K. , Walker S.
Published: May 2006

Dielectric absorption studies have been made of group relaxation of acetophenone, 1,4-diacetylbenzene,4-acetylbiphenyl, and 2-acetylfluorene in a polystyrene matrix, and two rigid molecules have also been examined. For acetyl group relaxation in acetophenone, ΔHE = 29.6 ± 0.6 kJ mol−1 and ΔSE = 26 ± 3 JK−1 mol−1 (95% confidence intervals). The energy barrier for acetyl group relaxation is of the same order as that obtained from nmr data. Our results for acetophenone differ appreciably from the values reported for the gaseous phase by the far-infrared approach and from those by the dielectric absorption of aromatic ketones in benzene solution. The enthalpies of activation for acetyl group relaxation in 1,4-diacetylbenzene, 4-acetylbiphenyl, and 2-acetylfluorene are 29, 30, and 32 kJ mol−1, respectively, which values are identical within their experimental errors. These three substances have also been examined as pure solids, yielding enthalpies of activation for acetyl group relaxation of a similar magnitude.
Cyclopropanediols. VI. Obtention de dérivés du cyclopropanediol
Authors: Goaller Raymond Le , Pierre Jean-Louis
Published: May 2006

Two methods are described for the preparation of substituted cyclopropanediols: reduction of β-diketones, and bridging of 1,2-bissiloxyalkenes; a number of the latter compounds were prepared by a new method. [Journal translation]
Selective, homonuclear pulse experiments in the Fourier transform mode: a study of 2′,3′-O-isopropylidene uridine
Authors: Bock Klaus , Burton Roland , Hall Laurance D.
Published: May 2006

A simple modification of a conventional Fourier transform nmr spectrometer (Varian XL-100) makes it feasible to apply selective, radiofrequency pulses at the resonance frequency of one, or more, proton resonances and to monitor the effects of those perturbations in the usual F.t. fashion. Experiments with 2′,3′-O-isopropylidene uridine are used to illustrate the utility of this technique in measurements of selective spin-lattice relaxation rates, to eliminate unwanted resonances by selective saturation or by selective partial relaxation, and to perform the pulse equivalent of a 1H–1H INDOR experiment.
Studies in the usnic acid series. IV. The base catalyzed usnic acid – isousnic acid rearrangement. Part II. An improved synthesis of (+)-isousnic acid
Authors: Kutney James P. , Sanchez Ignacio H. , Yee Trevor
Published: May 2006

Investigations concerning the alkaline cleavage of (+)-2H-[1,2]oxazocinousnic acid (3) are described. These studies provide an interesting rearrangement from the 'normal' (usnic acid) to the 'iso' (isousnic) series and, in turn, a high yielding sequence for the synthesis of (+)-isousnic acid (1).
Molecular structures of dichloro(dimethyl)germane and trichloro(methyl)germane determined by vapour phase electron diffraction
Authors: Drake John E. , Hencher J. Lawrence , Shen Quang
Published: May 2006

The molecular structures of dichloro(dimethyl)germane and trichloro(methyl)germane have been determined in the vapour phase by electron diffraction. The principal geometrical parameters for (CH3)2GeCl2 are rg(Ge—Cl) = 2.143 ± 0.004 Å, rg(Ge—C) = 1.928 ± 0.006 Å, [Formula: see text].and [Formula: see text] In the analysis of CH3GeGl3 recently reported values of the rotational constants were combined with the electron diffraction data to give rg(Ge—Cl) = 2.132 ± 0.003 Å, rg(Ge—C) = 1.893 ± 0.010 Å, [Formula: see text] and [Formula: see text]In both cases the methylgermane geometry was assumed for the methyl group [Formula: see text] which was fixed in the staggered configuration with respect to the C2GeCl2 and CGeCl3 frames respectively. Both random and systematic errors were included in the uncertainty estimates, which are believed to be approximately at the 95% confidence level. In the case of (CH3)2GeCl2 the uncertainties in [Formula: see text] were enlarged to four times the least-squares values in order to reflect the difficulty of resolving the Cl … Cl, C … Cl, and C … C distances in the analysis.
Synthesis and crystal structure of diiodotetraethylthiuramdisulfidemercury(II)
Authors: Chieh Chung
Published: May 2006

Reaction of mercury(II) iodide with tetraethylthiuramdisulfide in chloroform and ethanol mixed solvent produced bis(iodo-N,N-diethyldithiocarbamatomercury(II)) and diiodotetraethylthiuramdisulfidemercury(II), HgI2.TETD. The crystal of HgI2.TETD is orthorhombic with a = 13.101(9), b = 13.999(9), c = 22.742(15) Å; space group Pbca. The structure was solved with 1960 observed reflections measured by a G.E. XRD-6 diffractometer. The final R factor was 0.064. The mercury atom is four-coordinated with two identical Hg—I distances of 2.668(1) Å and two Hg—S distances of 2.670(7) and 2.737(7) Å. The coordination is tetrahedral.
The stereochemistry of the Wittig reactions of allylic phosphoranes and phosphonate esters with aldehydes
Authors: Gedye Richard Neville , Westaway Kenneth Charles , Arora Parkash , Bisson Robert , Khalil Aly Hamdy
Published: May 2006

Methyl Z- and E-4-bromo-3-methylbut-2-enoate 13 and 14 react with triethyl phosphite stereospecifically with retention of configuration to give the corresponding Z- and E-phospho-nate esters 8 and 9. The Z- and E-phosphonates react with aldehydes with extensive stereomutation of the double bond. Rapid equilibration to a mixture of one part E-phosphonate to two parts Z-phosphonate occurs when either geometric isomer is treated with base. Despite this, the E-2,E-4 ester 16 is the chief product of the reaction. Methyl E-β-ionylideneacetate 16b is the major product of the reaction of either isomer with β-cyclocitral and with cyclohexene car-boxaldehyde only the E-2,E-4 isomer 16c is formed. Benzaldehyde reacts with the phosphonates to give a mixture of the E-2,E-4 and Z-2,E-4 isomers 16a and 15a in a 4:1 ratio. Although the corresponding Z- and E-phosphonium salts 6 and 7, obtained stereospecifically from the bromo esters, react by the same general mechanism as the phosphonates the main product with benzaldehyde is the Z-2,Z-4 isomer 17a.
Nucleic acid related compounds. 25. Syntheses of arabino, xylo, and lyxo-anhydro sugar nucleosides from tubercidin ribo-epoxide
Authors: Robins Morris J. , Fouron Yves , Muhs Wolfgang H.
Published: May 2006

Treatment of the trans iodohydrin acetate, 4-amino-7-(3-iodo-3-deoxy-2-O-acetyl-5-O-[2,5,5-trimethyl-1,3-dioxolan-4-on-2-yl]-β-D-xylofuranosyl)pyrrolo[2,3-d]pyrimidine (2) with metha-nolic ammonia gave 2′,3′-anhydrotubercidin (3) in 96% yield. N4,N4,O5′-Tribenzoylation of 3 gave 4, which is stabilized against intramolecular cyclization. Treatment of 4 with boron tri-fluoride etherate (3′,5′-benzoxonium ion formation) followed by deblocking gave 4-amino-7-β-D-xylofuranosylpyrrolo[2,3-d]pyrimidine (5) in 91% overall yield from tubercidin (1). The 3′,5′-O-isopropylidene derivative (6a) of 5 was mesylated to give 6b which was deprotected in acid and the resulting trans hydroxy mesylate was treated with base to give 4-amino-7-(2,3-anhydro-β-D-lyxofuranosyl)pyrrolo[2,3-d]pyrimidine (7). This lyxo epoxide was treated with sodium benzoate in DMF to give 4-amino-7-β-D-arabinofuranosylpyrrolo[2,3-d]pyrimidine (8). Biochemical, spectroscopic, and chemical properties of these semisynthetic antibiotic analogues of biologically active adenine nucleosides are discussed.
Nuclear magnetic resonance relaxation and anisotropic reorientation in liquid dimethylmercury
Authors: Lassigne Claude R. , Wells E. J.
Published: May 2006

Spin–lattice relaxation times of 1H, D, and 199Hg have been measured between 234 and 333 K in liquid dimethylmercury and its isotopic modifications. These measurements have allowed the relaxation mechanisms to be separated. It was found that the spin–rotation interaction is the dominating mechanism for the 199Hg relaxation at 14.1 kG even at low temperatures. We have estimated the spin–rotation constants, [Formula: see text] along with the chemical shift anisotropy [Formula: see text]It is concluded that reorientation about the symmetry axis is not well described by molecular diffusion. Reorientation of the methyl group about its symmetry axis is found to be approximately forty times faster than the reorientation about the perpendicular axis.
Thermodynamic parameters for the basic ionization of some cyclic amines in water
Authors: Lobo Sheila Teresa , Murty Tanikella S. S. R. , Robertson Ross Elmore
Published: May 2006

not available
Straining strained molecules. II. The syntheses and spectral properties of some ace-bridged naphthalenes
Authors: Mitchell Reginald H. , Fyles Thomas , Ralph Leonard M.
Published: May 2006

Reaction of both peri-dilithionaphthalene and peri-dilithioacenaphthalene with acenaphthenequinone and pyracenequinone yielded the dihydroxy derivatives of acenaphth[1,2-a]-acenaphthylene 11a, 11b, 11c with no, one, and two ace-bridges respectively. These could be converted either by the Corey thionocarbonate method or with anhydrous liquid hydrogen fluoride to the three alkenes 12a,b,c and with Pb(OAc)4 to the three diketones 13a,b,c. The latter on Wolff–Kishner reduction yielded alkenes 12a,b and mono ketones 15b,c. The uv, ir, 1Hmr spectra and electrode reduction potentials for the four series of compounds in which the ace-bridges add increments of strain were examined and possible effects which might be due to strain were noted. Several areas in which theoretical calculations are lacking were noted.