bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemotherapeutic agents. XIX. Synthesis of [1,2,4]‐Triazoloquinazolinones and related compounds as antihypertensive agents
Authors: Ram V. J. , Srimal R. C. , Kushwaha D. S. , Mishra L. 
Published: January 2005

AbstractA series of 1,2,4‐triazolo[4,3‐a]quinazolin‐5‐ones have been prepared to assess their therapeutic utility as CNS depressant, spasmolytic and hypertensive agents.
Studies on 1,3‐indandione: Synthesis of Fluorenones and Indeno(2,1‐c)pyridazine
Authors: Sofan Mamdouh A. , El‐Taweel Fathy M. , Elagamey Abdel Ghani A. 
Published: January 2005

Abstract1,1‐Dicyanomethylene‐3‐indanone (2) reacted with cinnamonitriles 1a‐c to afford fluorenone derivatives 6a‐c. Compounds 6a‐c were also obtained when treating 2 with 1d‐f. The coupling of 2 with aromatic diazonium chlorides resulted in the formation of the hydrazones 8a‐c. 8a readily cyclized to indeno[2,1‐c]pyridazine (9a) in acidic medium. The action of 1d‐f on enaminone 3 was also studied.
Photoreduction of Methyleneblue by the two‐equivalent electron donor N‐methyl‐9‐phenylacridane and the use of the system for the spectrally sensitized dediazoniation of p‐N,N‐dimethylamino benzenediazonium tetrafluoroborate
Authors: Becker H. G. O. , Kohrs K. 
Published: January 2005

AbstractThe photoreduction of methyleneblue by N‐methyl‐9‐phenylacridane (ACH) is studied in acetonitrile by means of flash photolysis and quantum yields. In the first step, due to fast proton shift within the original electron transfer product protonated semi‐methyleneblue MBH.+ and the deprotonated donor radical (N‐methyl‐9‐phenylacridanyl radical AC·) are formed with a rate constant of 2×108 M−1 s−1. In this radical pair a second electron is transferred very fast from AC· to MBH.+ with a rate constant ke2 ≈︂ 1010 s−1 to form leuco‐methyleneblue and N‐methyl‐9‐phenyl‐acridinium salt (AC+). About 80% of the two‐equivalent reduction product, leuco‐methyleneblue, are formed within the first solvent cage during the flash. The maximum quantum yields of photoreduction approach φisc of MB+ as expected for a two‐equivalent reduction reaction.The out‐of‐cage reaction consists of the known disproportionation of the protonated semi‐methyleneblue MBH.+ and its reduction by the N‐methyl‐9‐phenylacridanyl radical AC·. From the decay kinetics kred = 3×109 M−1 s−1 and kdis = 8×108 M−1 s−1 is derived.The system sensitizes the dediazoniation of p‐N,N‐dimethylamino benzenediazonium tetrafluoroborate efficiently even at very low diazonium salt concentrations (Φ = 0.6).
Zur thermischen Cyclisierung und Aromatisierung von Hex‐1‐en‐5‐in
Authors: Remmler M. , Ondruschka B. , Vorwerk D. , Olk B. , Pola J. , Kubat P. 
Published: January 2005

On the Thermal Isomerization and Aromatization of Hex‐1‐ene‐5‐yneThe gas phase conversion of hex‐1‐ene‐5‐yne induced by conventional hot‐wall pyrolysis, very low pressure pyrolysis (VLPP‐MS technique) and continuous‐wave CO2 laser‐photosensitized (SF6) pyrolysis was studied at 350–1100°C.The pyrolysis experiments were performed in quartz reactors and the reaction products analyzed by capillary gas chromatography, mass and n.m.r. spectroscopy. The pattern of conversion suggested for all the processes involved a sequence of isomerizations (→hexa‐1,2,5‐triene→methylcyclopentenes), aromatization (into benzene via pentafulvene) and CC bond rupture (into propargyl and allyl radicals).The formation of benzene is explained by reaction network with methylenecyclopentenes and methylcyclopentadienes as key intermediates.
Synthesis of Substituted Crown‐Ethers by radical addition of 18‐crown‐6
Authors: Zeleconok Ju. B. , Orlovskij V. V. , Zlotskij S. S. , Rachmankulov D. L. 
Published: January 2005

AbstractAn example of the synthesis of substituted crown‐ethers by radical addition reaction of 18‐crown‐6 (1) to several α‐olefins (2a‐e), cyclohexene (2f), vinyl butyl ether (2g), allyl alcohol (2h), trimethylvinylsilane (2i), diethylmaleate (2j) and formaldehyde (2k) in the presence of a peroxide initiator was studied.The dependence of the yield of the addition product upon reaction conditions was also investigated.
Reduction of Long Chain and Bulky Carboxylic Esters by sodium tetrahydroborate
Authors: Giumanini Angelo G. , Tubaro Franco 
Published: January 2005

AbstractMethyl esters of long chain fatty acids as well as esters with functional (OH) and/or bulky substituents in alpha position and in the OR moiety may be effectively reduced with an excess of sodium tetrahydroborate at moderate temperature in dioxane‐water without catalysts. The reaction has been applied to the reduction of a pool of triglycerides of natural origin (virgin olive oil) in order to obtain a mixture of the acyl residues reduced to the corresponding alcohols without any structural or configurational modification. They, no matter which was the advancement of the reaction, seemed to reproduce quite well the overall acyl composition, as shown by GC‐MS analysis: the feasibility of such quantitative analysis may be extended, in order to obtain confirmatory evidences, on the component identifications and to perform specific separations, to the corresponding chlorides, hydrocarbons and trimethylsilylethers.
Substituent effect on “Ring‐Chain” tautomerism of 1,2,3,4‐Tetrahydro‐s‐tetrazines
Authors: El‐Abadelah M. M. , Hussein A. Q. , Abushamleh A. S. 
Published: January 2005

AbstractMethylhydrazones (III) of aromatic aldehydes and ketones react with nitrile imines (II) to give 1,2,3,4‐tetrahydro‐s‐tetrazines IV (1‐9) which exhibits “ring‐chain” tautomerism in solution. The extent of this tautomerism is dependent both on steric and electronic effects of substituent groups at C‐3 and C‐6 ring carbons.
Preparation and characterization of 1,5‐Diacyl‐2,4‐dioxohexahydro‐1,3,5‐triazines with Higher Acyl Groups
Authors: Hofmann Jörg , Just Gerhard , Pritzkow Wilhelm 
Published: January 2005

AbstractThe title compounds were prepared from 2,4‐dioxohexahydro‐triazine (DHT) and the corresponding acid chlorides in the presence of sulphuric acid. They are active acylating agents against piperidine in dioxane as the solvent. Only the diacyl derivatives of DHT with acyl chain lengths up to C6 react with aqueous solutions of sodium perborate forming the corresponding peroxy acids.
Acyllerung von N‐(2, 6‐Dimethylphenyl)‐α‐alaninmethylester mit sp‐hybridisierten Kohlensäurederlvaten
Authors: Martin D. 
Published: January 2005

Acylation of N‐(2, 6‐Dimethylphenyl)‐α‐alanine Methylester with sp‐hybridized Carbonic Acid Derivatives.The title compound 5 reacts with isocyanates and isothiocyanates to yield the substituted imidazolidinones 7 and 8, respectively, whereas with chlorosulfonyl isocyanate the open chained urea 9 is formed. Cyanation of 5 takes place with phenyl cyanate and cyanogene bromide. Consecutive reactions of the primary products are described.
Nitriles in heterocyclic synthesis: Synthesis of pyrazolo[1, 5‐a] pyrimidine, pyrazolo[1, 5‐c][1, 2, 4]triazine and pyrazolo[4, 3‐e][1, 2, 4]triazine derivatives
Authors: Ali Elagamey Abdel Ghani , El‐Taweel Fathy Mohamed Abdel‐Aziz 
Published: January 2005

Abstract5‐Amino‐3‐phenylpyrazole (1) reacted with enaminonitriles 2a–c to afford the pyrazolopyrimidines 5a, b and the 5‐substituted aminopyrazole 8. 5a reacted with arenediazonium chlorides and benzaldehyde to give 6 and 7 respectively. Also, o‐hydroxyacetophenone afforded the fused pyrazole derivative 9 on treatment with 1. Enaminonitrile 3 coupled with 11 and arenediazonium chlorides to give 12 and 13 respectively. Cyclization of 13a, b afforded the pyrazolotriazines 15a, b.
Nitriles in organic synthesis: The Reaction of Cinnamonitriles with cyclohexanone and acetylacetone
Authors: El‐Sakka I. A. , El‐Kousy S. M. , Kandil Z. E. 
Published: January 2005

AbstractThe reaction of 1 a, b with cyclohexanone afforded hexahydronaphthalene derivatives (3 a, b). In contrast to the behaviour of 1 a, b, cyclohexanone reacts with 4a–c to yield the propenylidenecyclohexanone derivatives (5a–c). The reaction of 1a with acetylacetone gives 4H‐pyran 6 and a 1:2‐adduct 8 a. On treatment of 8 a with sodium metal in the presence of dioxane, the pyrano [2, 3‐b]pyridine (9a) was obtained. When 1 b, c reacted with acetylacetone, the only isolable products were 8 b,c. Reaction of 4a with acetylacetone gives acyclic compound 10. This on treatment with basic reagents, gives the pyran derivative (13).
Thioharnstoffverbindungen und Metallkomplexe aus N‐Thiocarbamoylbenzimidoylchloriden
Authors: Beyer Lothar , Hartung Jürgen , Köhler Ronald 
Published: January 2005

Derivatives of Thioureas and Metal Complexes from N‐Thiocarbamoyl‐benzimidoyl Chlorides.The reactions of nickel(II)‐coordinated N‐benzoyl‐thioureas with acid chlorides are described. With different nucleophiles the title compounds N‐thiocarbamoyl‐benzimidoyl‐chlorides yield N‐thiobenzoyl‐thioureas, N‐thiocarbamoyl‐benzimido(thio)esters and N‐thiocarbamoyl‐benzamidines as chelating agents, respectively. By cyclisation 1,3,5‐thiadiazin‐2‐thiones and 1,2,4‐triazoles were obtained. The formation, structure and bonding situation of the ligands and the transition metal complexes are discussed. 1,2,4‐Dithiazolium‐halometalates, 1,3,5‐oxadiazinium salts and selenium analogous are included in this review.
Tetranuclear Thioureacopper(II) Complexes
Authors: Makáňová Darina , Kováčik Ivan , Ondrejovič Gregor 
Published: January 2005

AbstractBy replacement of methanol in the Cu4OX6(MeOH)4 (X  Cl, Br) complexes with thiourea (tu), N,N′‐diphenylthiourea (diftu), N,N′‐dimethlthiourea (dimtu), tetramethylthiourea (tmtu) and acetylthiourea (actu), the complexes Cu4OCl6L4 where L  tu, tu(0.3 Et2O), diftu, dimtu, tmtu, actu (0.5Et2O) and the complexes Cu4OBr6L4, where L  tu, diftu, dimtu, tmtu have been prepared. Their infrared and electronic spectra indicate the presence of Cu4O grouping and the trigonal bipyramidal coordination of copper(II). These complexes exhibit e.p.r. signals in the temperature range 100–260 K, in contrast to other known complexes of this structural type, which showed the e.p.r. signals at significantly lower temperatures. Thiourea and its derivatives are not able to reduce copper(II) in reaction with the tetranuclear Cu4OX6(MeOH)4 complexes in methanol‐ether solution due to the redox stabilizing effect of the tetranuclear structure.
Synthese und Eigenschaften neuartiger Alkalimetall‐Alkoxo‐ und ‐Aroxocobaltate(II)
Authors: Ibrahim Aisha Ismail , Gaube W. , Kalies W. , Witt B. 
Published: January 2005

Synthesis and Properties of Novel Alkali Metal Alkoxo‐ and Aroxocobaltates(II).By reaction of CoBr2 or CoBr2 · 2THF with 4–5 moles of MOR in THF, M  Li, Na, K, R = iso‐propyl (iPr), phenyl (Ph), 2‐naphthyl (2‐Naph), the following novel alkali metal alkoxo‐ and aroxocobaltates(II) have been prepared.Li2Co(OiPr)4 · LiBr · 3THF (1), Na2Co(OiPr)4 · THF (2), KCo(OiPr)3 · THF (3), Li2Co(OPh)4 · 4THF (4), Na2Co(OPh)4 · 5THF (5), K2Co(OPh)4·0,75THF (6), Li2Co(O‐2‐Naph)4 · 4THF (7), Na2Co(O‐2‐Naph)4 · 5THF (8), K2Co(O‐2‐Naph)4 · 2THF (9), and K3Co(O‐2‐Naph)5 · 2THF (10).The blue and violet, crystalline and very air‐sensitive (i.e. protolytically sensitive) compounds, some with good solubilities in organic solvents, eliminate THF in vacuo at temperatures between 50 and 100°C to yield the corresponding THF‐free compounds (1a) to (10a).Electronic spectra (VIS/NIR) and the results of magnetic measurements at 293 K point to preferred (but not exclusive) tetrahedral coordination of cobalt(II).
Studies on the oxidation of enamines with molecular oxygen. III. Oxidation of some amino styrenes
Authors: Blau K. , Burgemeister I. , Grasnick J. , Voerckel V. 
Published: January 2005

AbstractIn the oxidation of the amino styrenes 1a–1j only products of the oxidative attack at the C  C double bond and hydrolysis products are obtained. Aprotic dipolar solvents and the addition of molecular sieve 5A promote the oxygen uptake. The addition of hydrochinone to the oxidation system does not influence the rate of oxygen absorption or the yields of the oxidation products.
Sulfochlorierung von 1,2‐Naphthochinondiazid‐(2) mit Chlorsulfonsäure
Authors: Sauer E. , Polz K. , Schopf G. , Bendig J. 
Published: January 2005

Sulfochlorination of 1,2‐Naphthoquinone‐(2)‐diazide by Chlorosulfonic acid.The sulfochlorination of 1,2‐naphthoquinone diazide‐(2) (1) by chlorosulfonic acid was investigated. The yields of the formed products (1,2‐naphthoquinone diazide‐(2)‐4‐sulfonic acid (4), 1,2‐naphthoquinone diazide‐(2)‐5‐sulfonic acid (5), 1,2‐naphthoquinone diazide‐(2)‐4‐sulfochloride (2) and 1,2‐naphthoquinone diazide‐(2)‐5‐sulfochloride (3)) depend on the temperature and on the time of reaction. The highest yields of the favoured 1,2‐naphthoquinone diazide‐(2)‐4‐sulfochloride (2) are obtained at 63°C and after a reaction time of 80 minutes (50%).
119Sn‐NMR spektroskopische Untersuchungen an Tributylzinnderivaten aromatischer Sulfonsäuren
Authors: Thunecke Frank , Borsdorf Rolf 
Published: January 2005

119Sn‐NMR Spectroscopic Investigations of Tributyltin Derivatives of Aromatic Sulfonic Acids.Tributyltin derivatives of nine aromatic sulfonic acids were synthesized and investigated by means of 119Sn‐n.m.r. spectroscopy. 119Sn‐chemical shifts and 1J (Sn, C) coupling constants in dependence on temperature and concentration were applied to study the association processes of the substances in solution. In CDCl3 as a solvent a monomeric/polymeric equilibrium of the substances was demonstrated, while CD3OD as a donor solvent forms five‐coordinated complexes with the tin compounds.
The Influence of DDT‐Preventing Agents upon the Impact Sensitivity of the polyurethane‐bonded RDX
Authors: Wen Li , Quancai Song , Wenbin Wang , Yongke Chen 
Published: December 2004

AbstractThe effect of some DDT‐preventing agents (DPAs) and their mixtures on the impact sensitivity of RDX/PU has been studied. All specimen for drop‐hammer test were prepared by solvent‐slurry method. Two ways were used in adding DPA. The behavior of moulding powders obtained to the mechanical impact were assessed using KAST Impact Hammer. The results have shown that some DPA decreased the impact sensitivity of RDX/PU with different degree, and the loading way of DPA also had obvious effect on it. Finally, the characteristic heights H50 and the remained quantities of samples after impacting were analyzed and discussed.
Pulsed Laser Induced Decomposition of Energetic Polymers: Comparison of ultraviolet (355 nm) and infrared (9.3 μm) initiation
Authors: Haas Yehuda , Ben‐Eliahu Yeshayahu , Welner Shmuel 
Published: December 2004

AbstractIrradiation of the energetic polymer GAP (glycidyl azido polymer) by a high power pulsed UV laser leads to its rapid decomposition. A large amount of solid and gaseous material is released, and in the presence of an inert gas, a shock wave develops. Comparison with an inert polymer indicates that the energy released by the exothermicity of the decomposition reaction contributes significantly to the shock formative energy. The energy released in the micro‐explosion can be estimated from the analysis of the shock front propagation velocity. It is found that irradiation of polymers in which GAP is diluted by an inert polymer, may lead to a higher shock intensity than irradiation of neat GAP. Possible causes for this apparent inconsistency (which is not observed upon initiation by a pulsed infrared laser) are discussed.
The influence of post‐exposure temperature on the toxicity of insecticides to Ostrinia nubilalis (Lepidoptera: Crambidae)
Authors: Musser Fred R , Shelton Anthony M 
Published: January 2005

AbstractThe influence of post‐treatment temperature on the toxicities of two pyrethroids (lambda‐cyhalothrin and bifenthrin), a carbamate (methomyl) and a spinosyn (spinosad) to Ostrinia nubilalis (Hübner) larvae was evaluated in laboratory assays. From 24 to 35 °C, the toxicities of the pyrethroids decreased 9.5‐ and 13.6‐fold while spinosad toxicity decreased 3.8‐fold. The toxicity of methomyl did not change significantly. The results demonstrate that the most effective insecticide against a pest may vary with environmental conditions. In situations where comparable products from multiple insecticide classes are available, temperature should be included as a factor in the decision‐making process. Copyright © 2005 Society of Chemical Industry
The group theoretical approach to nuclear quadrupole resonance
Authors: Boyle L. L. 
Published: December 2004

AbstractThe phenomenon of nuclear quadrupole resonance is presented from the grouptheoretical point of view. This approach allows one to discuss the splitting of the nuclear spin states without prior wave‐mechanical calculation. Nuclear quadrupole moments are also compared with moecular quadrupole moments and the differences discussed. Finally the selection rules are deduced.
Frequency‐dependent polarizability of open‐shell atomic systems
Authors: Roy H. P. , Gupta A. , Mukherjee P. K. 
Published: December 2004

AbstractThe time‐dependent variational principle is used to calculate the frequency‐dependent dipole polarizabilities of 2p open‐shell atomic systems. A general theory is built up to include frequency‐dependent perturbations using the Roothaan–Hartree–Fock (HFR) formalism. The excitation energies corresponding to the low‐lying excited states of the system are obtained from the poles of the dynamic polarizability values. A fairly accurate knowledge of transition oscillator strengths is also obtained from a knowledge of the polarizability values near the poles. The excitation energies and oscillator strengths are compared with available data.
The spin‐orbit interaction in the configuration nlNn'l using nonorthogonal radial orbitals
Authors: Jucys A. P. , Sabas K. V. , Kupliauskis Z. J. 
Published: December 2004

AbstractFormulas for the calculation of matrix elements of the simplified operator of the spin‐orbit interaction for the configuration n1lNn2l are deduced for the case when radial orbitals are nonorthogonal. The coefficients of the radial integrals are tabulated for the configuration pNp. The fine structure of the excited configuration of the carbon atom is calculated.
Orbital optimisation in single open‐shell configurations: A sequential unconstrained minimisation technique
Authors: Mukherjee Debashis 
Published: December 2004

AbstractA simple algorithm for optimising the orbitals for single open‐shell configurations which utilises a sequential unconstrained minimisation technique (SUMT) suggested by Morrison is presented in this paper. As numerical illustrations, the orbitals of the lowest π – π* singlet and triplet (Ms = 0) states of three conjugated hydrocarbons are optimised by the algorithm. The advantages of using the SUMT method are also emphasised.
Operator formalism for forming ket vectors under some constraints
Authors: Morikawa Tetsuo 
Published: December 2004

AbstractReformulation, generalization, and application of Löwdin's symmetric orthonormalization, of orthogonalization of two sets of vectors, and of McWeeny's variational method of a density matrix, etc., by means of an operator for forming ket vectors on which are imposed some conditions, are presented.
Orbit‐orbit molecular integrals over Gaussian orbitals
Authors: Lo B. W. N. 
Published: December 2004

AbstractAnalytical formulas are derived for integrals of the orbit‐orbit operator in the Breit‐Pauli Hamiltonian. The present method differs from an earlier one in the introduction of a new auxiliary function Gn(a) which is an integral of Shavitt's Fm(t) function. A method for its evaluation is discussed and some numerical examples are given.
Upper and lower bounds to critical values of the Hartree operator
Authors: Behling R. , Bongers A. , Küpper T. 
Published: December 2004

AbstractUpper and lower bounds for the minimal critical energy E of the Hartree operator for helium are calculated. We show that a Ritz analogous procedure for the calculation of the upper bounds converges to the exact value. The lower bound to E yields that the ground state EH of the helium atom is strictly lower than 2E.
A model for the helix–coil transition of DNA
Authors: Porta Jordi 
Published: December 2004

AbstractThe helix–coil phase transition of DNA is studied through a model equivalent to the one used in the theory of superconductivity. A distribution function for the excitations analogous to the usual Fermi function is obtained which depends on the parameter T0, the maximum temperature at which all pairs of bases are bonded. The expression for the number of unbonded pairs of bases depends only on the two parameters, T0 and Tc (critical temperature).
Molecular orbital calculations of metal ion interaction with nucleic acid bases. I. Binding of Cu(II) with adenine, guanine, uracil, and cytosine
Authors: Kothekar V. , Dutta S. 
Published: December 2004

AbstractThe reaction of the transition metal ion Cu(II) with nucleic acid bases—adenine, guanine, uracil, and cytosine—has been investigated by conformation energy calculations (CEC) and molecular orbital (MO) methods. Various binding sites, e.g., N7–C6NH2, N7–C6O, N3‐N9, and N1 in purines and N3 and O8 in pyramidines, have been considered. It was found that the energy minima for different binding sites had different values. In addition to the energy minima in the nucleic acid base plane, we have observed out‐of‐plane energy minima, differing in energy by a few kcal/mol in most of the cases. The MO calculations were performed on the most favorable planar positions obtained. It was found that the presence of Cu(II) alters the charge distribution pattern of practically all the atoms of nucleic acid bases. Its main effect is to withdraw electrons from the negatively charged nitrogens and positively charged carbons. The oxygen charge did not alter significantly. The results are compared with the experimental electron spin resonance and x‐ray diffraction studies and their biological significance is discussed.
The antisymmetrized product of weak nonorthogonal geminals
Authors: Lyast I. Ts. 
Published: December 2004

AbstractMost commonly the nonorthogonality of geminals is weakly expressed so that the exchange and overlap integrals ζ(η), φ(η) are negligible for large exchange parameters η. The conditions which allow the terms with large η to be discarded are considered. The integrals ζ(η), φ(η) are derived for η = 2, 3, 4.
On the non‐existence of maxima in variational computations containing non‐linear parameters
Authors: Tal Yoram , Katriel Jacob 
Published: December 2004

AbstractThe homogeneity properties of the kinetic and potential energy operators are used to obtain expressions for the second derivatives of the energy expectation value. These are used to demonstrate that in atoms as well as in molecules in the neighborhood of the equilibrium geometry the variational energy cannot have maxima with respect to the non‐linear parameters.
On the concept of “Partitions” in the perturbation theory of n‐electron systems
Authors: Schmidt H. M. 
Published: December 2004

AbstractThis paper deals with the perturbation theory of an n‐electron Hamiltonian of the general form H = ∑n ƒ(i) + λ∑n g(i, j) = H (f, g; n). In comparison to the Brueckner–Goldstone diagrammatic perturbation theory, we adopt the more general standpoint of admitting, for the construction of an n‐particle state, component states of 1, 2, 3, and more particles [O. Sinanoglu, Phys. Rev. 122, 493 (1961) and C. D. H. Chisholm and A. Dalgarno, Proc. R. Soc. (London) Sec. A 292, 264 (1966)]. We show that this leads to the concept of a “partition” of a perturbational eigenstate (or energy) of H. A “partition” is a natural decomposition which: (i) is finite; (ii) relates the eigenvalue problem of the system H = H (f, g; n) to those of certain subsystems H (f, g; n1)(n1 < n); (iii) uses “nonseparable” components. We domonstrate (under the preliminary assumption of “strict” nondegeneracy) the second‐order energy to possess a “partition.” The components therein are second‐order energies of two‐ and three‐particle states. The proof uses an extension of Racah's concept of the fractional‐parentage expansion.