bluuebunny/crossref_metadata_2025 huggingface dataset:
Some reactions of a 4-(1-chloroethyl)-1,4-dihydropyridine
Authors: Gregory Brian , Bullock Eric , Chen Teng-Song
Published: May 2006

The preparation of dimethyl 4-(1-chloroethyl)-1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylate and its reaction with nucleophilic reagents are described. Potassium cyanide, potassium succinimide, or methanolic triethylamine gave, stereospecifically, 4,5-dihydroazepines in which substituents at C(4) and C(5) are trans, whereas potassium thiocyanate afforded only the corresponding 4-(1-thiocyanatoethyl)-1,4-dihydropyridine. Sodium hydrosulfide afforded a mixture of 8-thia-2-azabicyclo[3.2.1]oct-3-ene-4,7-diesters epimeric at C(7), whereas potassium carbonate in aqueous dimethyl sulfoxide yielded an 8-oxa-2-azabicyclo-[3.2.1]oct-3-ene-4,7-diester. The stereochemistry of these bicyclic compounds is established using nmr spectroscopy. In acid media, dimethyl 2,5,7-trimethylazepine-3,6-dicarboxylate and a 4-methoxy-4,5-dihydroazepine rearranged to give 1,4-dihydropyridine derivatives; a mechanism for this ring contraction is suggested.
The addition of 2,4-dinitrobenzenesulphenyl chloride to 1,3-disubstituted allenes: a reexamination
Authors: Garratt Dennis G. , Beaulieu Pierre
Published: May 2006

The reaction of 2,4-dinitrobenzenesulphenyl chloride with eight alkyl 1,3-disubstituted allenes in methylene chloride solution has been investigated. In contrast to earlier reports, attack by sulphur is found to occur exclusively at the central allenic carbon. The direction of approach of sulphenyl chloride leads preferentially to the formation of the E isomers in accord with the concept of steric approach control. The ratio of E to Z alkene is found to increase as the bulk of the substituent group cis to the arylthio group increases. We observe, however, very little regioselectivity with respect to which of the mutually perpendicular π bonds of the allene system is attacked, suggesting the presence of an effective mechanism for transmission of inductive effects to the more distant double bond.
Electrical conductance and thermal behaviour of some manganese(II) carboxylates
Authors: Adeosun Samuel Oluyemi
Published: May 2006

Data are presented on the heats of phase transitions and electrical conductances of the even chain length manganese(II) carboxylates from octanoate to octadecanoate inclusive. The total entropy change for the transition crystal → isotropic liquid is small indicating a high degree of aggregation in the isotropic liquid. This behaviour is similar to that of the cadmium carboxylates.Plots of log specific conductivity against inverse temperature show curvature. Attempts to fit the data to the Vogel–Tammann–Fulcher equation[Formula: see text]showed non-random deviations. Instead, the data were interpreted in terms of a simple dissociation equilibrium for which the enthalpy change is ∼240 kJ mol−1.
Molybdenum, tungsten, and manganese carbonyl compounds incorporating novel tridentate chelating dimethyl(1-pyrazolyl)(ethanolamino)gallate ligands
Authors: Chong Kenneth S. , Storr Alan
Published: May 2006

The coordinating properties of the tridentate tris-chelating ligand, [Me2Ga(OCH2CH2NH2)(N2C3H3)]−, and its three methyl substituted derivatives (methyl substitution on the amino nitrogen and the 3,5 positions of the pyrazolyl ring) have been studied in a series of molybdenum, tungsten, and manganese carbonyl compounds. Mixed allyl carbonyl and nitrosyl carbonyl compounds of both molybdenum and tungsten have been characterized, and a series of tricarbonyl manganese compounds studied. All the complexes are monomeric octahedral species having the tris-chelating ligands in fac coordination. Steric factors influence the arrangement of the three remaining groups in the mixed octahedral complexes (i.e. allyl carbonyl and nitrosyl carbonyl derivatives) and particular site preferences are inferred from spectroscopic measurements.
The crystal and molecular structure of 1,4-diphenyl-2,2′,3,3′,5,5′,6,6′-octamethylcyclo-1,4-diphospha-2,3,5,6-tetrasilahexane, a phosphorus–silicon heterocycle
Authors: Cordes A. Wallace , Schubert Paul F. , Oakley Richard T.
Published: May 2006

The crystal structure of 1,4-diphenyl-2,2′,3,3′,5,5′,6,6′-octamethylcyclo-1,4-diphospha-2,3,5,6-tetrasilahexane, (PhPSi2Me4)2, has been determined by single crystal X-ray diffraction. The crystals are monoclinic, space group P21/c, with a = 9.866(1), b = 11.921(1), and c = 11.324(2) Å, β = 104.31(1)°, Z = 2, and ρcalcd = 1.15 g/cm3. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to a final R of 0.060 and Rw of 0.078, for 1173 reflections with intensities greater than 3σ. The (PhPSi2Me4)2 molecule lies on a crystallographic centre of symmetry, and the six-membered P2Si4 ring has a chair conformation with equatorial phenyl groups. The endocyclic angles at P (104.4(1)°) and Si (104.9(2)°) are intermediate between those found in cyclic hexaphosphine and hexasilane molecules, and the Si—Si and P—Si distances of 2.345(3) and 2.252(4) Å, respectively, correspond to single bond lengths, with no appreciable evidence for secondary pπ → dπ bonding between phosphorus and silicon. The Si—C (1.867(8) Å) and P—C (1.828(7) Å) bond lengths are also normal. The variations in the Si—P—C (101.6(2)°, 108.6(2)°), P—Si—C (range 106.2(3)–120.0(3)°), and Si—Si—C (range 105.8(3)–113.7(3)°) angles indicate that the positions of the exocyclic methyl and phenyl groups are influenced by both intra- and intermolecular steric forces.
The role of electron–phonon interaction and non-Gaussian transport in spectral changes of trapped electrons in glasses
Authors: Funabashi Koichi , Hamill William H.
Published: May 2006

The continuous-time-random-walk (CTRW) model which was developed for electron scavenging reactions in polar glasses is extended to the phenomenon of spectral relaxation of electrons in shallow traps et− in a wider range of systems. The central role of electron-phonon coupling in understanding the initial electron localization, the "pre-existing trap", and electron transfer processes are emphasized. The reactivity of et− with scavengers, including protons, is discussed in terms of the theory of multi-phonon non-radiative transitions.
The preparation and properties of some thioacylmethylenethiazolines and isothiazolines
Authors: McKinnon D. M. , Hassan M. E. , Chauhan M. S.
Published: May 2006

Thiazoline-2-thiones and isothiazoline-3-thiones are converted into the 2- or 3-thiophenacylidene derivatives, respectively, by reaction with phenacyl bromide, treatment with pyridine, and thionation. The former compounds react with dimethyl acetylenedicarboxylate to form mono- and diadducts as well as some decomposition products. Attempts to demonstrate valency isomerism in the 3-thiophenacylideneisothiazoline derivatives were unsuccessful.
The synthesis of peptides related to a conserved sequence found in histone H-1 and H-5. Their ability to act as substrates and inhibitors of exogenous protein kinases
Authors: Kielland Sandra L. , Mathiaparanam Ponnampalam , Slotin Lewis A. , Williams Ross E.
Published: May 2006

Two peptides, H-Gly Ser Phe Lys-NH2 and H-Gly Ser Phe Lys Leu-NH2, whose sequence may be found in a conserved and phosphorylated site in histone H-1 have been synthesized. Their ability to act as substrates for several protein kinase preparations have been examined. In addition, their ability to inhibit the action of several protein kinases of muscle origin was also tested.
Hydrogen–deuterium exchange in tetrahydroborate salts
Authors: Oxton Ian A. , McInnes A. Gavin , Walter John A.
Published: May 2006

1H nmr spectroscopy has been used to demonstrate hydrogen–deuterium exchange in solutions of NaBH4/NaB2H4 in diglyme and KBH4/KB2H4 in 18-crown-6 ether/chloroform. Earlier observations of such exchange with LiBH4/LiB2H4 in an ethereal solvent were confirmed. Spectra were simplified by broadband decoupling of deuterium, facilitating quantitative measurement of the degree of exchange.
The conformation and reorientation of enclathrated 1,2-dichloroethane
Authors: Garg S. K. , Davidson D. W. , Gough S. R. , Ripmeester J. A.
Published: May 2006

The rigid-lattice nmr line shape of the four-proton system in 1,2-dihaloethanes has been obtained by spectral simulation as a function of dihedral angle [Formula: see text] and used to show that 1,2-dichloroethane is encaged in the structure II hydrate in a gauche configuration with [Formula: see text] Very broad low-temperature dielectric absorption is associated with an average activation energy of 0.87 kcal/mol for guest-molecule reorientation.
The enol content of simple carbonyl compounds: a kinetic approach
Authors: Guthrie J. Peter
Published: May 2006

Following a suggestion of Lienhard and Wang, we demonstrate that the enol content of simple carbonyl compounds can be estimated as the ratio of the rate constants for acid-catalyzed enolization of the carbonyl compound and acid-catalyzed hydrolysis of the corresponding methyl enol ether. Values so estimated are in excellent agreement with those determined by our thermochemical method. Sufficient data are available for the following; compound, pKEnol: acetaldehyde, 4.7; propionaldehyde, 4.2; isobutyraldehyde, 2.7; acetone, 7.0; cyclopentanone, 6.7; cyclohexanone, 5.3; cycloheptanone, 7.2; cyclooctanone, 6.6; p-nitroacetophenone, 4.9; p-bromoacetophenone, 6.2; acetophenone, 6.6; p-methylacetophenone, 7.0; p-methoxyacetophenone, 7.3; and by estimating the rate constants for enolization, the following; indanone, 7; 2-phenyl-2-propanone, 4; cyclopropyl methyl ketone, 8; chloroacetaldehyde, 2 (corrected for hydration); phenylacetaldehyde, 2.
The reactivity of allyl and propargyl alcohols with solvated electrons: temperature and solvent effects
Authors: Afanassiev Alexei M. , Okazaki Kiyoshi , Freeman Gordon R.
Published: May 2006

The rate constants k1 for the reaction of solvated electrons with allyl alcohol in a number of hydroxylic solvents differ by up to two orders of magnitude and decrease in the order tert-butyl alcohol > 2-propanol > 1-propanol ≈ ethanol > methanol ≈ ethylene glycol > water. In methanol and ethylene glycol the rate constants (7 × 107 M−1 s−1 at 298 K) and activation energies (16 kJ/mol) are equal, in spite of a 32-fold difference in solvent viscosity (0.54 and 17.3 cP, respectively) and 3-fold difference in its activation energy (11 and 32 kJ/mol, respectively). The reaction in tert-butyl alcohol is nearly diffusion controlled and has a high activation energy that is characteristic of transport in that liquid (E1 = 31 kJ/mol, Eη = 39 kJ/mol). The activation energies in the other alcohols are all 16 kJ/mol, and it is 14 kJ/mol in water. They do not correlate with transport properties. The solvent effect is connected primarily with the entropy of activation. The rate constants correlate with the solvated electron trap depth. When the electron affinity of the scavenger is small, a favorable configuration of solvent molecules about the electron/scavenger encounter pair is required for the electron jump to take place. The behavior of the rate parameters for propargyl alcohol is similar to that for allyl alcohol, but k1, A1, and E1 are larger for the former. The ratio k(propargyl)/k(allyl) at 298 K equals 10.5 in water and decreases through the series, reaching 1.3 in tert-butyl alcohol. Rate parameters for several other scavengers are also reported.
Photolyse du méthyl-2-butène-1, du méthyl-3-butène-1 et du cis-pentène-2 à 174, 163 et 147 nm
Authors: Collin Guy J. , Deslauriers Hélène , Auclair Sylvain
Published: May 2006

Photolysis of 2-methyl-1-butene (M2B1), cis-2-pentene (CP2), and 3-methyl-1-butene (M3B1) has been systematically studied at 163 nm. Pressure effect has been measured at 147, 163, and 174 nm. The main fragmentation process of the photoexcited olefine is the C—C split of the bond located in position β relative to the double bond:[Formula: see text] α-Methallyl radicals obtained in the M3B1 and CP2 photolysis decompose partly at low pressure, giving rise to the formation of 1,3-butadiene and hydrogen atoms. β-Methallyl radicals decompose also at low pressure into allene and methyl radicals. Butadiene and allene quantum yields follow the Stern–Volmer law, and this allows us to determine the ratio of the rate constant of dissociation relative to the rate constant of stabilization, kd/ks, through collision of the α- and β-methallyl radicals. From these values, we conclude that the excess of photon energy is not statistically distributed into the fragments, and that the decomposition process follows one (or several) particular law(s).
Electronic excited states of small ring compounds. VII. Bicyclo[2.1.0]pentanes by the photocycloaddition of 1,2,3-triphenylcyclopropene to fumaro- and maleonitrile
Authors: Wong P. C. , Arnold D. R.
Published: May 2006

Irradiation of the charge-transfer complex between 1,2,3-triphenylcyclopropene (1) and fumaronitrile (7) and maleonitrile (8) leads to formation of bicyclo[2.1.0]pentane cycloaddition products (9, 10, 11) and the photoene product (12). These products were also formed when the reaction was photosensitized (triplet–triplet transfer). The structure of the adducts was established by analysis of 13C and 1Hmr spectra. Nuclear Overhauser effect studies were also useful. The triplet energies of 7 and 8 (ET ca. 50 kcal mol−1) were determined by studying the photosensitized isomerization as a function of sensitizer triplet energy. The thermal stability of the new bicyclo [2.1.0]pentanes has been studied, particularly with regard to the isomerization resulting from cleavage of the central [0] bond in these strained systems. The mechanism of the photocycloaddition reactions is discussed.
The fine structure of the Kolmogoroff–Avrami theorem
Authors: Smith Arthur , Fletcher Stephen
Published: May 2006

The fundamental processes underlying phase changes at electrode surfaces are often described in terms of the Kolmogoroff–Avrami theorem.Some aspects of the 'fine structure' of this theorem are considered. Particular attention is paid to the case of two-dimensional nucleation and growth under the influence of an applied electrode potential (equivalent to supersaturation). A probabilistic analysis is presented for circularly-symmetric nuclei which obviates the need for concepts such as 'overlap' between emergent nuclei. The concept of a 'collision front' is introduced which is defined as the line of contact along which neighbouring nuclei collide. It is shown that for instantaneous nucleation (potentiostatic double step method) the extended set of collision fronts constitutes a net composed of irregular convex polygons. The properties of this net are investigated in some detail. In particular, the extent of applicability of the Kolmogoroff–Avrami equation is delineated, the distribution of collisional polygons is calculated, and an approximate treatment for the variance of the surface coverage function is presented. The general approach exposes clearly the relationship between the single nucleus and the multinuclear situations.
Crystal and molecular structure of (η3-2-methylallyl)[dimethyl(ethanolamino)-(3,5-dimethyl-1-pyrazolyl)gallato(N(2),N(3),O)] dicarbonylmolybdenum, [Me2Ga(N2C5H7)(OCH2CH2NH2)]Mo(CO)2(η3-C4H7)
Authors: Chong Kenneth S. , Rettig Steven J. , Storr Alan , Trotter James
Published: May 2006

Crystals of (η3-2-methylallyl)[dimethyl(ethanolamino)(3,5-dimethyl-1-pyrazolyl)gallato-(N(2),N(3),O)]dicarbonylmolybdenum are triclinic, a = 7.6047(5), b = 10.882(1), c = 12.633(1) Å, α = 77.07(1), β = 89.19(1), γ = 71.91(1)°, Z = 2, space group [Formula: see text]. The structure was solved by Patterson and Fourier syntheses and was refined by full-matrix least-squares procedures to R = 0.024 and Rw = 0.030 for 3835 reflections with I ≥ 3σ(I). The crystal structure consists of discrete molecular units, each linked to four others by weak [Formula: see text] hydrogen bonds [Formula: see text] The Mo atom is in a distorted octahedral environment with the η3-C4H7 ligand occupying one of the six coordination sites as a π-donating ligand. Important bond distances (corrected for libration) are: Mo—C(allyl), 2.335(3), 2.372(3), 2.324(3); Mo—C(O), 1.902(3) and 1.961(2); Mo—O, 2.269(2); Mo—N(pz), 2.222(2); Mo—N(amino), 2.285(2); Ga—O, 1.924(2); Ga—N, 2.006(2); and Ga—C, 1.968(4) and 1.981(4) Å.
Estimation of the fraction of dative structure in molecular complexes using Hammett ρ values
Authors: Poh Bo-Long
Published: May 2006

A simple method of estimating the fraction of dative structure in molecular complexes using Hammett ρ values is given. A physical interpretation of the parameter m in the equation, hν = mID + n, relating the charge-transfer energy, hν, of a molecular complex and the ionization potential, ID, of the donor is given.
Stereochemistry of the Bucherer–Bergs and Strecker reactions of tropinone, cis-bicyclo[3.3.0]octan-3-one and cis-3,4-dimethylcyclopentanone
Authors: Trigo Gregorio G. , Avendaño Carmen , Santos Emilia , Edward John T. , Wong Sin Cheong
Published: May 2006

The tropane-3-spiro-5′-hydantoin (α isomer) obtained from tropinone by the Bucherer–Bergs reaction has been shown by 13C nmr and X-ray diffraction studies to have the 4′-carbonyl group in the equatorial position; the β isomer, obtained via the Strecker reaction, has this group axial. The results of these two reactions on cis-bicyclo[3.3.0]octan-3-one and on cis-3,4-dimethylcyclopentanone show, on the basis of the 1H nmr, 13C nmr, and X-ray diffraction studies of the products, a stereochemical course related to the preferred conformation of the cyclopentane rings.
Total synthesis of spirobenzylisoquinoline alkaloids. Part V. Generalized approach to the complete set of alkaloids
Authors: Dime David , McLean Stewart
Published: May 2006

The strategy outlined previously has been developed to provide, in principle, routes to any known spirobenzylisoquinoline alkaloid. The generality has been demonstrated by the synthesis of the racemic forms of corydaine, yenhusomidine, corpaine, sibiricine, and raddeanone.
The total synthesis of (±)-luciduline
Authors: Szychowski Jerzy , MacLean David B.
Published: May 2006

(±)-Luciduline has been synthesised in seven steps from 2-(2-cyanoethyl)-5-methylcyclohex-2-en-1-one. The synthetic approach is adaptable to the synthesis of intermediates of interest in biosynthetic studies of the Lycopodium alkaloids.
Berberidic acid
Authors: Chinnasamy P. , Shamma M.
Published: May 2006

Berberidic acid (2), obtained by nitric acid oxidation of berberine (1), can be esterified to diester 3, or to monoesters 4 and 5. Sodium borohydride reduction of 4 provides γ-lactone 6 which can be oxidized with iodine to pyridinium salt 7. In like fashion, monoester 5 leads to γ-lactone 8 which is oxidized by mercuric acetate to salt 9. Berberidic acid dimethyl ester (3) is hydrogenated to allo hexahydro diester 10 from which normal diester 11 can be derived by base isomerization. Hydrogenation of lactone 6 produces allo lactone 14 whose further reduction with lithium aluminum hydride gives diol 15. This same diol can also be obtained from the lithium aluminum hydride reduction of hexahydro diester 10. Alternatively, lithium aluminum hydride reduction of diester 11 gives rise to diol 16, diastereomeric with 15. Catalytic hydrogenation of lactone 8 provides normal lactone 18 which is transformed to diol 6 by lithium aluminum hydride.
Studies on the syntheses of heterocyclic compounds. Part 782. Another total synthesis of (±)-tubulosine and (±)-deoxytubulosine
Authors: Kametani Tetsuji , Suzuki Yukio , Ihara Masataka
Published: May 2006

(±)-Tubulosine (1) and (±)-deoxytubulosine (3) were totally synthesized by the Pictet–Spengler reaction of (±)-4-oxoprotoemetine (7) with serotonin (8) or tryptamine (9) followed by reduction with sodium bis(2-methoxyethoxy)aluminum hydride in pyridine.
Perturbed normal-mode analysis of induction times, relaxation times, and reaction rates in unimolecular reactions
Authors: Yau Andrew W. , Pritchard Huw O.
Published: May 2006

A perturbed normal-mode analysis is presented of the induction (or incubation) time, the relaxation rate, and the reaction rate of a diluted unimolecular system. At high temperature, the unimolecular rate approaches the Lindemann behaviour and the low-pressure rate is related to the normal modes of relaxation of the reactive states in a simple manner. In a step-ladder model system, the network relationship between the normal modes and the microscopic transition probabilities leads to explicit theoretical correlations between the respective experimental quantities. Illustrative calculations of such correlations are presented for the decomposition reactions of N2O and CO2 diluted in Ar at shock wave temperatures, and are compared with experiment.
On the planarity of the NSi3 skeleton in the trisilylamine molecule. A normal coordinate analysis involving complex symmetry coordinates
Authors: Shurvell H. F. , Dunham A. , Cyvin S. J. , Brunvoll J.
Published: May 2006

Normal coordinate calculations have been carried out for the N(SiH3)3 molecule. A model with C3h symmetry was used, which is based on a planar NSi3 skeleton. The presence of complex numbers for the characters of degenerate irreducible representations of the point group C3h leads to an unusual problem when factoring the G and F matrices. A set of real degenerate symmetry coordinates for the E′ and E′′ species can be constructed, but these are not true symmetry coordinates under the C3h point group. However, they can be obtained from the genuine (complex) symmetry coordinates by a unitary transformation. For a degenerate species, this procedure leads to a and b blocks of the factored G and F matrices, which contain interaction terms. Consequently both blocks must be taken together when forming the secular equation, and subsequently the calculated frequencies appear as pairs of identical numbers.A valence force field that includes all reasonable interactions has been obtained and used to predict the wavenumbers of the 15N and d9 isotopic molecules. Details of the normal vibrations in the three molecules have been obtained from potential energy distributions. The results show reasonable agreement with the limited experimental data available for the isotopic molecules.
Reaction of alanine-3-sulfinic acid with 2-mercaptoethanol
Authors: Finlayson Alexander J. , MacKenzie Samuel L. , Finley John W.
Published: May 2006

The reaction of alanine-3-sulfinic acid with 2-mercaptoethanol (2-ME) was examined at pH 1.5 and pH 4.0 at 110 °C. The sulfinic acid is readily reduced at pH 1.5 to cysteine, 2-L-amino-7-hydroxy-4,5-dithiaheptanoic acid, cystine, and three other ninhydrin positive substances. The reduction is much slower at pH 4.0; the major reaction product is the 2-ME/cysteine mixed disulfide. The results show that 2-ME at acid pH does not give quantitative reduction of alanine-3-sulfinic acid to cysteine.
Stannic tetrachloride catalysed glycosylation of 8-ethoxycarbonyloctanol by cellobiose, lactose, and maltose octaacetates; synthesis of α- and β-glycosidic linkages
Authors: Banoub Joseph , Bundle David R.
Published: May 2006

The 1,2-trans-octaacetates of cellobiose, lactose, and maltose were converted to β-glycosides of 8-ethoxycarbonyloctanol in good yield by a single step reaction. A 1,2-acetoxonium ion generated by stannic tetrachloride in dichloromethane at −10 °C leads initially to β-glycosides via 1,2-orthoacetate intermediates. Insitu anomerisation of the β-maltoside occurred during reaction (4 h) at room temperature and provided a preparative route to this α-glycoside of the disaccharide. The β-lactose and cellobiose glycosides were also anomerised to the respective α-glycosides. The three β- and three α-disaccharide glycosides of the disaccharides have been functionalised for conversion to artificial carbohydrate antigens.
A spectrophotometric study of the complex formation between cobalt(III) and trans-1,2-cyclohexanedinitrilotetraacetic acid (CyDTA)
Authors: Hessley Rita K. , Waykole Shoba , Sublett Robert L.
Published: May 2006

An intriguing and unique system has been observed during the otherwise routine study of the cobalt(III) complex of trans-1,2-cyclohexanedinitrilotetraacetic acid (CyDTA). Using classical spectrophotometric methods to determine the stoichiometry and the stability of a complex, significant deviations from the predicted 1:1 complex were observed in a system buffered at pH = 4.6. It is postulated that in addition to the usual 1:1 complex, the propensity of the reactants to form complexes and the strong oxidizing conditions used in this investigation result in the formation of a second, higher order complex between Co(III) and CyDTA. When the concentration of CyDTA exceeds that of Co(III), the metal:ligand ratio for this complex is 1:2. A structure is proposed, and approximate stability constants of both complexes are discussed.
Some reactions of 10-substituted-10H-pyrido[3,2-b][1,4]benzothiazine-n-butyllithium adducts with acyl and sulfonyl chlorides
Authors: Pasutto Frank M. , Knaus Edward E.
Published: May 2006

Reaction of 10H-pyrido[3,2-b][1,4]benzothiazines 1 possessing a 10-methyl 1f, 10-(3-dimethylaminopropyl) 1b, or 10-(2-dimethylaminopropyl) 1c substituent, with n-butyllithium and methyl chloroformate or diethyl chlorophosphate affords predominantly 1,2-dihydropyridines 11 and the 4-substituted derivatives 12. The 1,7-disubstituted product 15b was obtained from reaction of the 10-methyl compound 1f with p-fluorobenzoyl chloride. On the other hand, treatment of the 10-methyl analog 1f with trifluoromethanesulfonyl chloride gave the unexpected 4-chloro derivative 12c and 13c which probably arises from the 1-trifluoromethanesulfonyl-1,2-dihydropyridine 11c via elimination of trifluoromethanesulfonic (sulfinic) acid. The N-10 dealkylated product 1a was obtained from reaction of the 10-(1-methyl-2-dimethylaminoethyl) analog 1g with n-butyllithium and methyl chloroformate, whereas a similar reaction employing the 10-(2-dimethylaminoethyl) derivative 1h gave rise to the N-methoxycarbonyl derivative 18. On the other hand, reaction of 1h with n-butyllithium alone gave the N-10 n-hexyl product 19. Mechanisms for the formation of 1a, 11, 12, 13, 15, 16, and 19 are described.
Stereochemical aspects of the Pummerer reaction. Diastereotopic selectivity in the deprotonation of oxysulfonium cations
Authors: Wolfe Saul , Kazmaier Peter Michael
Published: May 2006

The diastereomeric RS/SR- and RR/SS-benzyl-α-d methyl sulfoxides have been subjected to the Pummerer reaction with acetic anhydride and with trifluoroacetic anhydride. The ethoxysulfonium fluoroborate derivatives of these sulfoxides have been subjected to the Pfitzner–Moffatt reaction with sodium hydride in tetrahydrofuran. The deuterium contents of the starting materials and of the Pfitzner–Moffatt product have been determined by mass spectrometry. The deuterium contents of the α-acyloxybenzyl methyl sulfoxides formed in the Pummerer reaction have been determined by 1Hmr spectroscopy. The resulting data permit the calculation of the diastereotopic selectivities and isotope effects associated with the deprotonation of oxysulfonium cations. The selectivities are found to be lower by a factor of about 10 than those observed in the formation of the benzyl-α-d methyl sulfoxides by hydrogen–deuterium exchange of benzyl methyl sulfoxide. Nevertheless, the existence of selectivity in the Pummerer reactions rules out a sulfurane and a dication as sole product-determining intermediates. The factors contributing to this low selectivity are discussed.
The conformations of furanosides. A 13C nuclear magnetic resonance study
Authors: Cyr Natsuko , Perlin Arthur S.
Published: May 2006

A study of the conformations of 15 methyl aldohexo- and pentofuranosides in aqueous solution has been carried out, based primarily on measurements of coupling by 13C-1 and 13C-2 with protons of the five-membered ring. From these stereochemically-dependent data, and their correspondence with vicinal 1H–1H couplings, the conformation favored by each glycoside has been deduced. Although, in general, the coupling patterns exhibited by homologous pairs of hexoses and pentoses are closely similar, the α-gluco and α-xylo pair provide an exception: their data indicate that the latter favors the 2E conformation, whereas the glucoside is characterized by interconverting E4 and 3E conformers. It appears that a quasi-equatorial exocyclic side chain and a quasi-axial C-1,O-1 bond (anomeric effect) are equally important stabilizing factors in furanosides. In a number of instances, the current findings differ from those obtained in earlier studies for configurationally-related furanose derivatives in organic media.
Analysis of trace metal impurities in phthalocyanine pigments
Authors: Loutfy Rafik O. , Hsiao Cheng-Kuo
Published: May 2006

An analytical procedure was developed to determine the content of metallic impurities in metal-free phthalocyanine (H2Pc) pigments. The technique involves dissolving the pigment in concentrated sulfuric acid, followed by oxidative degradation using hydrogen peroxide. Phthalimide was the only organic oxidation product. The remaining trace metals in the solution were determined using plasma atomic emission. The trace metals content in a commercial α polymorph of phthalocyanine pigment (ICI-Monolite Fast Blue GS) was monitored as a function of purification processes. Experiment showed that Monolite Fast Blue contains 2500 ppm Na; 350 ppm Ca, and 370 ppm Fe. Purification of this material by extraction with hot dimethyl-formamide gave β-H2Pc, which contained 300 ppm Na, 110 ppm Ca, and 310 ppm Fe. Sulfuric acid purification (acid pasting) reduced the content of non-transition elements, but in-increased the content of transition metals.These results were compared to the trace metal content in H2Pc pigment which were synthesized.
Electron scattering cross sections of gaseous pentanes and hexanes
Authors: Freeman Gordon R. , György István , Huang Sam S.-S.
Published: May 2006

Electron scattering cross sections σv have been estimated as functions of electron velocity v for six gaseous pentanes and hexanes. The scattering cross section of each compound has a minimum in the vicinity of υ = (2–3) 107 cm/s, corresponding to an electron energy of 0.1–0.2 eV. For the pentanes, the scattering cross sections on the low energy side of the minimum increase with increasing sphericity of the molecules, while the minimum tends to shift to higher energies. The same is true of the hexanes.
Hydrogen bond assisted reactions: C- and O-alkylations, sulphenylations, and Michael additions aided by polymer immobilized fluoride ion
Authors: Miller Jack M. , Cater Stephen R. , So Kwok-Hung , Clark James H.
Published: May 2006

Hydrogen bond assisted C- and O-alkylations, sulphenylations, and Michael additions have been carried out with the aid of fluoride ion immobilized on strongly basic anion exchange resins.
Density and temperature effects on electron mobilities in gaseous butene isomers
Authors: Wada Toshinori , Freeman Gordon R.
Published: May 2006

The density normalized mobilities μn at low electric field strengths in the low density gases fall in the order trans-2- > cis-2- > 1- > isobutene. The respective values in the saturated vapors at 297 ± 1 K were 10.7, 4.4, 3.8, and 1.84 (1022 molecules/cm V s). The scattering cross section σv has a Ramsauer–Townsend-like minimum at an electron energy of 0.085 eV in trans-2-butene, 0.13 eV in cis-2-butene, 0.12 eV in 1-butene, and 0.16 eV in isobutene. The mobilities in the last three isomers increase with increasing temperature (300–500 K) and field strength [Formula: see text]. Temperature and field effects were smaller in trans-2-butene. The ratio of the field effect threshold drift velocity to the speed of sound in the low density gas is 14, 19, 20, and > 50 in iso-, 1-, cis-2-, and trans-2-butene, respectively, at 297 K. The electrons are de-energized mainly by inelastic collisions. Quasilocalization occurs to a similar extent in each of the isomers at densities [Formula: see text] and temperatures near the coexistence curve. Quasilocalization is characterized by large, negative values of ΔH and ΔS, and a small value of ΔG over a small temperature range.
Synthesis and spectroscopic studies of the pyrimidine-2(1H)thione derivatives
Authors: Al-Hajjar Farouk H. , Al-Farkh Yusuf A. , Hamoud Hayat S.
Published: May 2006

1,3-Diaryl-2-propen-1-ones 1 reacted with thiourea in the presence of sodium ethoxide to give 4,6-diaryl-3,4-dihydropyrimidine-2(1H)thiones 5 which upon dehydrogenation with 3 mol of ethanolic sodium ethoxide yielded the corresponding 4,6-diarylpyrimidine-2(1H)thiones 9. The N-acetyl derivatives of the former thiones were prepared. Infrared, nuclear magnetic resonance, and ultraviolet spectral data of the above compounds were tabulated and discussed.
An unusual carbomethoxyl migration from nitrogen to carbon. Formation of a 2H-pyrrole from AlCl3-promoted reaction of 1-carbomethoxy-2,5-dimethylpyrrole with dimethyl acetylenedicarboxylate
Authors: Matheson R. A. F. , McCulloch A. W. , McInnes A. G. , Smith D. G.
Published: May 2006

The AlCl3-promoted reaction of methyl 2,5-dimethylpyrrole-1-carboxylate 1 with dimethyl acetylenedicarboxylate affords under certain conditions a low yield of 2,5-dimethyl-2-tricarbomethoxyvinyl-2H-pyrrole 3. The structure of the latter was established on the basis of detailed 1H and 13C nmr studies, and confirmed by conversion to dimethyl 5-methyl-5-(3-oxobutyl)-3-pyrrolin-2-one-3,4-dicarboxylate 4.
Further studies on the use of the thallium salt of N-hydroxysuccinimide for the preparation of succinimidyl esters
Authors: Paquet Alenka
Published: May 2006

An efficient preparation of four alkyl (ethyl, tert-butyl, p-nitrobenzyl, trichloroethyl) succinimidyl carbonates from the thallium salt of N-hydroxysuccinimide and corresponding chloroformates is described. The general utility of trichloroethyl succinimidyl carbonate is demonstrated by its reaction with glycine to give trichloroethoxycarbonylglycine. The preparation of succinimidyl esters of numerous fatty acids using the thallium salt of N-hydroxysuccinimide and the corresponding acid chlorides is described. The advantage of this method over the N,N′-dicyclohexylcarbodiimide method for the preparation of these esters is demonstrated. Succinimidyl p-toluenesulfonate and chloroacetate were also prepared.
Etude empirique de la stabilité des hydrocarbures polycycliques non alternants
Authors: Gastmans Jean Pierre , Gastmans Denise Fromanteau , Slade Stéfano Fernandes
Published: May 2006

An empirical method for the prediction of the stability of hydrocarbons has been detailed. This method is based on the works of Krygowski and Randic.
Effect of pressure on the Raman spectrum of s-trioxane I and II
Authors: Nakahara M. , Wong P. T. T. , Lewis G. J. , Whalley E.
Published: May 2006

The Raman spectrum of trioxane II at ∼110 K and zero pressure, and the effect of pressure up to 21 kbar on the spectrum of trioxane I and up to 25 kbar on the spectrum of trioxane II, have been measured to determine if the puckered ring of trioxane goes flat. It does not. In trioxane II, many of the bands that are degenerate in the free molecule are split, showing that the C3 axis of the isolated molecule does not exist. A few volumetric measurements were made on the I–II boundary line.
Gas phase ion equilibria: heats of formation of acylium ions RCO+ and protonated acids RC(OH)2+; gas phase catalysis of proton shift RC(OH)2+ → RCO(OH2)+
Authors: Davidson W. R. , Meza-Höjer S. , Kebarle P.
Published: May 2006

The equilibria [2]: [Formula: see text] for R = CH3, C2H5, and C6H5 were studied in a pulsed electron beam high ion source pressure mass spectrometer. van't Hoff plots led to ΔH2 values: (CH3), 24.6; (C2H5), 22.7; (C6H5), 21.9 kcal/mol. ΔHf(RC(OH)2+) were obtained from gas phase basicity ladders combined with the new ΔHf(t-butyl+) = 163 kcal/mol (Beauchamp). The ΔHf(RC(OH)2+) were: (CH3), 71.3; (C2H5), 63.6; (C6H5), 95.5 kcal/mol. Combination of ΔH2 with ΔHf(RC(OH)2+) leads to ΔHf(RCO+): (CH3), 153.7; (C2H5), 144; (C6H5), 174.6 kcal/mol. These results are in agreement with selected data from appearance potentials. The energies and structures of the participants in reaction [2] were calculated by MINDO/3 and STO-3G. MINDO/3 gave good agreement with ΔH2. The establishment of the equilibria [2] was unusually slow. A study of the kinetics revealed that k2f is approximately third order, unusually small, and has an unusually large negative temperature coefficient. Furthermore, reaction [2] was found to be catalyzed by RCOOH. An explanation of these observations is given by assuming that the proton shift RCO(OH2)+ → RC(OH)2+ has a large activation energy barrier in the gas phase. This barrier is removed by formation of a hydrogen bonded complex with RCOOH.
Total synthesis of steroids. Part 1. Ring A aromatic compounds. Regiocontrol in diene additions with 6-methoxy-1-vinyl-3,4-dihydronaphthalene
Authors: Das Jagabandhu , Kubela Rudolf , MacAlpine Gerald A. , Stojanac Žarko , Valenta Zdenek
Published: May 2006

A total synthesis of ring A aromatic D-homosteroids and the conversion of one of them to estrone and its derivatives are described. The key reaction is a catalysed addition of 6-methoxy-1-vinyl-3,4-dihydronaphthalene to 2,6-dimethyl-1,4-quinone which proceeds with orientation inversion compared to the thermal addition. Reactions with several other quinones are described. The synthetic sequence includes a hydride reduction in which an apparently more hindered carbonyl group of an enedione system is reduced preferentially. Cyclization of a 1,6-keto aldehyde under acidic conditions gives the desired acetyl cyclopentene derivative, while a predominant formation of cycloheptenones is observed when the same cyclization is performed with base.
Total synthesis of (±)-5β,8α- androst-9(11)-ene-3,17-dione
Authors: Kakushima Masatoshi , Allain Leonard , Dickinson Robert A. , White Peter S. , Valenta Zdenek
Published: May 2006

A total synthesis of (±)-5β,8α- androst-9(11)-ene-3,17-dione is described. The key step is a ring C forming SnCl4-catalyzed Diels–Alder reaction in which the geometry of the diene controls syn–anti stereochemistry while the catalyst guides the addition to the desired endo orientation. A preparation of ethyl E-2-methyl-4-oxo-2-butenoate and the dehydration of a tertiary allylic alcohol by the pyrolysis of the corresponding tosyl carbamate are also described.
Synthesis and reactions of 1-hydroxy-1-(pyridinyl)-2-propanones
Authors: Knaus Edward E. , Avasthi Kamlakar , Redda Kinfe , Benderly Abraham
Published: May 2006

Reaction of pyridinecarboxaldehydes 1 with α-ethoxyvinyllithium 2 affords 2-ethoxy-1-(pyridinyl)-2-propen-1-ols 3 which on hydrolysis with aqueous formic acid give pyridinyl α-hydroxyketones 4. Selenium dioxide oxidation of 4a and 4b provides pyridinyl α-diketones 9 which on condensation with o-phenylenediamine afford 3-methyl-2-(pyridinyl) quinoxalines 11. Pyridinyl α-hydroxyketones 4a and 4b react with hydroxylamines to yield a mixture of E- and Z-oximes 5 and 6.
On Ruhemann's Purple
Authors: Wigfield Donald C. , Buchanan Gerald W. , Croteau Stephen M.
Published: May 2006

The 1H nmr spectrum previously reported for Ruhemann's Purple is shown to be inconsistent with the accepted structure of this material. The discrepancy with the reported 1H nmr spectrum is shown to be due to the presence of a major impurity, identified as hydrindantin. Spectra (1H nmr, 3C nmr, ir, uv–visible) of Ruhemann's Purple, its protonated analogue DYDA, and other ninhydrin relatives are reported, and structural conclusions are based on these spectral data.
Ion mobilities and collision frequencies in gaseous CH3Cl, HCl, HBr, H2S, NO, and SF6: effects of polarity of the gas molecules
Authors: Sennhauser Eric S. , Armstrong David A.
Published: May 2006

Mobilities of positive and negative ions at 296 K have been measured at pressures in the range 50 to 1200 Torr. Least-means quares analysis of the pressure dependences gave the following mobilities normalized to a density of 2.69 × 1019 molecules cm−3: CH3Clμ+ = 0.39, μ− = 0.37; HCl 0.64, 0.59; HBr 0.48, 0.49; H2S 0.59, 0.60; NO 0.97, 1.53; SF6 μ− = 0.49 cm2 V−1 s−1. Except in one instance the ions exhibited a close to inverse dependence of mobility on gas density. The identifies of the ions are discussed in the light of high pressure mass spectrometric data from the literature. The dependence of the collision frequencies of the ions on μD/α1/2, the ratio of dipole moment to (polarizability)1/2 for the neutral gas molecules, was very similar to that observed previously by the ion cyclotron resonance technique at much lower pressures. The magnitudes of the collision frequencies at unit concentration are in reasonable agreement with predictions based on the ion–molecule collision rate theory of Barker and Ridge, but the dependence on μD/α1/2 is lower and closer to that predicted by ADO theory.
Infrared spectra of the ammonium ion in crystals. Part VII. Existence of symmetrically trifurcated hydrogen bond in ammonium halides
Authors: Knop Osvald , Westerhaus Wolfgang J. , Falk Michael
Published: May 2006

This investigation deals with the effect of temperature, between 10 and 293 K, on the ir spectrum of the NH3D+ probe ion in polycrystalline NH4SnF3, NH4CuSO3, cubic (NH4)2SiF6, and (NH4)2SnCl6. The results lead to the following conclusions. At 10 K these crystals contain symmetrically trifurcated [Formula: see text] bonds, i.e. bonds in which the N—H orientation of maximum probability is on the threefold axis. With increasing temperature these bonds lose progressively their symmetrically-trifurcated character to become highly bent, highly dynamic [Formula: see text]•bonds, and the strength of the hydrogen-bonding interaction increases. This is reflected in the decrease of the ND stretching frequency of the probe ion with increasing temperature, which is the opposite of the behaviour observed with normal (i.e. essentially straight) [Formula: see text] bonds.Re-determination of the room-temperature crystal structure of NH4CuSO3 has confirmed the correctness of the structure reported previously by Nyberg and Kierkegaard.
Viscosity of binary solutions of polar liquids
Authors: Stairs Robert A.
Published: May 2006

The viscosity of mixtures of water with a number of organic liquids and of some mixtures of two organics has been analysed in terms of its deviation from "ideality", expressed as ln H = ln η − (x1 ln η1 + x2 ln η2). For most of the systems the quantity ln H is a single-valued and linear, or nearly linear, function of the product y1y2, where[Formula: see text]representing mole fractions (with κ = 0), or volume fractions (κ = 1), or various compromises (0 < κ < 1). Neither extreme, nor any single compromise, expresses the behaviour of all the systems. A linear relation between 1/H and the relative excess volume, suggested on the basis of the free-volume theory of fluidity, is shown to represent approximately the behaviour of the mixtures of two organic liquids. It fails with the water–organic mixtures.
Asymmetric reduction of α,β-unsaturated iminium salts with 1,4-dihydronicotinamide sugar pyranosides
Authors: Baba Naomichi , Makino Taketoshi , Oda Jun'ichi , Inouye Yuzo
Published: May 2006

3,3,5-Trimethyl-2-cyclohexylidene iminium salts were reduced with 1,4-dihydronicotinamide sugar pyranosides to give optically active 3,3,5-trimethylcyclohexanone in enantiomeric excess ranging over 3–31%. The product stereochemistry changed sensitively with structural variation (including anomers, epimers, and deacetylation) of sugar residues. The reduction by more simplified chiral models, N1-(1′S,2′S)-2′-hydroxy- or acetoxycyclohexyl-1,4-dihydronicotinamide revealed that operation of the functional groups on the sugar moiety is not merely steric in nature for induction of chirality in the product.
A systematic investigation of the reaction of SiF2 with ethylene and six methyl-substituted ethylenes. II. Characterization of polymeric products, open chain organosilicon derivatives, and 1,2-disilacyclobutanes
Authors: Reynolds William F. , Thompson James C. , Wright A. P. Gerald
Published: May 2006

Polymers produced by the reaction of SiF2 with olefins have been characterized by 13C and 29Si nmr spectroscopy and have been found to have a regular head-to-tail structure with isolated SiF2 groups between olefin units. Only minor proportions of Si2F4 units are formed. The open chain organosilicon derivatives formed in the reaction are, with one exception, isomers of 1,2-disilacyclohexanes. The 1,2-disilacyclobutanes are formed stereospecifically with retention of alkyl stereochemistry. 19F chemical shifts can be predicted by additive chemical shift parameters for the effect of alkyl substitution.
A comparison of the stereochemistry and kinetics of thermolysis of R-(+)-laurolenic acid, R-(+)-laurolenal, and R-(+)-laurolenol
Authors: Crawford Robert J. , Tokunaga Hirokazu
Published: May 2006

The thermolysis of R-(+)-laurolenal (1) produces R-(+)-1,2,3-trimethylcyclopentene in high optical purity. The alcohol 3, at 297 °C, similarly produces the alkene R-(+)-4, but with mechanistic complications in that the formaldehyde produced oxidizes the alcohol 3 to the corresponding aldehyde 1. The alcohol 3-d2 was used to show the extent of aldehyde conversion by virtue of the formation of 4-d1. Comparison of the decarboxylation of the acid, decarbonylation of the aldehyde, and demethanalation of the alcohol gives relative rates of 9:2:1 at 297 °C.
Etude par rmn du proton et du carbone-13 de pyrimidines substituées. IV. Empêchement de rotation dans des N,N-diméthylamino-4 pyrimidines à l'état monoprotoné
Authors: Riand Jacques , Chenon Marie-Thérèse , Lumbroso-Bader Nicole
Published: May 2006

The free energy of activation for hindered rotation about the C—N exocyclic bond in some N,N-dimethylaminopyrimidine hydrochlorides has been determined by 1H and 13C nmr line-shape analysis.Monoprotonation of N,N-dimethylaminopyrimidines induces a large increase of the free energy of activation (from 14 to 24 kJ mol−1). This increase is larger for the 4-dimethylamino group than for the 2-dimethylamino group due to the predominance of the monoprotonated (N-1 H) form. Consequently, the difference of conjugation of the 4- and 2-dimethylamino groups with the pyrimidine ring is more pronounced in the monoprotonated species.
Organocation speciation. I. A comparison of the interactions of methylene blue and paraquat with bentonite and humic acid
Authors: Guy R. D. , Narine D. R. , deSilva S.
Published: May 2006

A model System composed of bentonite, humic acid (HA), polystyrene sulphonic acid (PSSA), methylene blue (MB), and paraquat was used to characterize the possible interactions of organocations in natural waters. The adsorption and desorption studies with bentonite indicated that the clay had a strong preference for the organocations over alkali and alkaline earth cations. Paraquat saturated the bentonite up to the cation exchange capacity whereas methylene blue did not completely saturate the clay but did form methylene blue aggregates on the clay surface. The aggregates could be readily removed by washing with distilled water. The organocation interactions with the anionic polyelectrolytes were more susceptible to changes in pH or ionic strength. Paraquat could be completely desorbed from HA and PSSA by raising the solution ionic strength to 0.1. Methylene blue could not be completely removed from the humic acid but could be removed from PSSA by raising the ionic strength to 0.1. The studies indicate that a combination of dialysis separations, variation of ionic strength, and spectrophotometric analysis could be used to determine the free paraquat and the bound paraquat susceptible to changes in environmental levels of pH and ionic strength.
Bimolecular production of gas phase ionic hydrates by ion cyclotron resonance spectroscopy
Authors: Clair R. L. , McMahon T. B.
Published: May 2006

The gas phase ion–molecule reactions of α,α,α′,α′ tetrafluorodimethyl ether both alone and in mixtures with water have been examined. The dominant feature of the ion chemistry of these mixtures is the sequential bimolecular production of the hydrated hydronium ion, H5O2+. Two independent mechanistic pathways for production of H5O2+ are outlined arising from reaction of H3O+ with (CF2H)2O and from CF2H—O=CHF+ with H2O. Implications for examination of solvent switching equilibria are discussed.