bluuebunny/crossref_metadata_2025_split huggingface dataset:
1,3‐Dipolar cycloaddition of diazocompounds to 1‐alkenylboronic esters
Authors: Jazouli Mohammed , Carboni Bertrand , Carrié Robert , Soufiaoui Mohammed , Toupet Loïc 
Published: January 2005

AbstractA variety of diazo compounds was added to the parent vinylboronic ester derived from pinacol. The reactivity of some substituted 1‐alkenylboronic esters is also briefly examined. The nonisolated primary adducts spontaneously rearrange via a 1,3‐boron migration and lead to 1‐borylated‐2‐pyrazolines. The structure of one of these compounds has been established by X‐ray diffraction analysis.
Methanolysis of 1,3‐oxathiolane‐2‐thione: A stereospecific preparation of episulfides
Authors: Uenishi Jun'ichi , Motoyama Mitsuhiro , Kubo Yuki 
Published: January 2005

AbstractPotassium carbonate mediated methanolysis of optically active 1,3‐oxathiolane‐2‐thiones (5‐membered cyclic xanthates) took place under very mild conditions to give optically pure 1,2‐episulfides. Also, methanolysis of 4‐[1‐(methanesulfonyloxy)alkyl]‐1,3‐oxathiolane‐2‐thiones and 2,4‐dialkyl substituted 1,3‐oxathiolane‐2‐thione gave 2,3‐episulfides, stereospecifically.
Oxidation of ketene‐S,S‐acetals, thioacetals, and thioketals by dimethyldioxirane: A convenient method for the preparation of bis‐sulfones
Authors: Curi Denise , Pardini Vera L. , Viertler Hans , Baumstark Alfons L. , Harden Donald B. 
Published: January 2005

AbstractThe oxidation of a series of ketene‐S,S‐acetals, 2a–f, and a series of thioacetals and thioketals, 4a–g, with a fourfold or greater excess of dimethyldioxirane, 1, produced the corresponding bis‐sulfones 3a–f and 5a–g in excellent yields. The reaction of the bis‐sulfides with one, two, and three equivalents of 1 yielded monosulfoxides, bis‐sulfoxides, and sulfoxide‐sulfones, respectively, as the major products. The order of addition of the reactants as well as the temperature of the reaction mixture changed the product distributions. The use of low‐temperature, rapid stirring and the addition of the dioxirane solution to the bis‐sulfide maximized the yield of the major product. The results are consistent with an electrophilic oxygen‐atom transfer mechanism in which the rate of sulfide oxidation is much faster than oxidation of sulfoxide to sulfone. However, sulfoxide oxidation is of a sufficient rate such that local concentration effects affect the results.
Synthesis of some new spiro[indoline‐3‐heterocycle]‐2‐one derivatives
Authors: Al‐Thebeiti Marzoog S. 
Published: January 2005

AbstractIndole‐2,3‐dione was treated with malonic acid in a mixture of ethanol/pyridine to afford 1‐[3‐(2‐oxoindolinylidene)]acetic acid (3), which was then reacted with thionyl chloride to give the corresponding acid chloride (4). The acid chloride 4 reacted with arenes in the presence of AlCl3 to yield substituted 3‐(2‐oxoindolinylidene)acetophenones 5a–c. Compounds 5a–c were alkylated with methyl iodide to afford 6a–c. Compounds 6a–c were treated with hydrazine derivatives, hydroxylamine hydrochloride, urea, and thiourea to yield the complex spiro compounds 7a–i, 8a–c, and 9a–f, respectively.
Oxidation of tetraphosphacubane by bis(trimethylsilyl) peroxide, sulfur, and selenium [1]
Authors: Ma Xiao‐Bo , Birkel Manfred , Wettling Thomas , Regitz Manfred 
Published: January 2005

AbstractAlthough the nucleophilicity/basicity at the phosphorus atom of the tetraphosphacubane 2 is reduced, apparently owing to the participation of the lone pairs of electrons in the P/C σ bonds, stepwise oxidation of the phosphorus atoms with bis(trimethylsilyl) peroxide or sulfur (in the presence of triethylamine) can be realized until all four phosphorus atoms have reacted to give products 10–17. When 2 was treated with a large excess of selenium at 110°C, only the triselenide 18 was obtained.
Palladium‐catalyzed hydrosilylation of silyl‐substituted butadienes
Authors: Weng Wu‐Wang , Chen Ruey‐Min , Luh Tien‐Yau 
Published: January 2005

AbstractPalladium‐catalyzed hydrosilylation of silyl‐substituted butadienes 1 and 2 with MeSiCl2H has been investigated. Both steric effects and the presence of an aryl substituent affect the regiochemistry of the hydrosilylation reaction. Hydrosilylation of siloxanetethered bis‐dienes 9 exhibits high regio‐ and diastereoselectivity.
Trans‐annular interactions in morpholines: A photoelectron spectroscopic study
Authors: Novak Igor , Kovaĉ Branka 
Published: January 2005

AbstractThe He I and He II photoelectron spectra of 4‐methylmorpholine, 4‐morpholinecarbonitrile, and 4‐morpholinepropionitrile have been measured. The electronic structure and heteroatom lone pair interactions, in particular, were analyzed with the aid of HeII/HeI intensity variations, comparison with the spectra of related compounds, and AM1 semiempirical calculations. We present an example of combined inductive and resonance interactions operating in the morpholine ring system.
Preparation, spectral characterization, and single crystal X‐ray structures of cis and trans isomers of 2,4,6‐trifluoroethoxy‐1,3,5‐triethyl‐1,3,5,2λ5, 4λ5, 6λ5‐triazatriphosphorinane‐2,4,6‐trioxide, [ETNP(O)(OCH2CF3)]3
Authors: Murugavel Ramaswamy , Thirupathi Natesan , Krishnamurthy Setharampattu S. , Nethaji Munirathinam 
Published: January 2005

AbstractOxidation of the cis isomer of the λ3‐cyclotriphosphazane [EtNP(OCH2CF3)]3 with trimethylamine‐N‐oxide (TMNO) gives the cis isomer of trioxo‐λ5‐cyclotriphosphazane [EtNP(O)(OCH2CF3)]3; the trans isomer of [EtNP(O)(OCH2CF3)]3 is obtained by the treatment of a cis and trans mixture of [EtNP(OCH2CF3)]3 with aqueous H2O2. The two trioxocyclotriphosphazanes have been characterized by elemental analysis, IR, and NMR (1H, 13C, 19F, and 31P) spectroscopy. The solid state structures of both the isomers have been determined by single crystal X‐ray diffraction. The six‐membered P3N3 ring in both the isomers exhibits a twist‐boat conformation; in the cis isomer, the trifluoroethoxy substituents lie on the same side of the ring, whereas, in the trans isomer, two trifluoroethoxy groups are on one side of the ring and the third on the other side of the ring. Crystal data for cis‐[EtNP(O)(OCH2CF3)]3: monoclinic, P21/n, a = 13.593(3), b = 9.721(2), c = 17.539(3) Å, β = 99.49(2)°, V = 2286(1) Å3, Z = 4, and Final R = 0.047. Crystal data for trans‐[EtNP(O)(OCH2CF3)]3: monoclinic, P21/n, a = 11.685(4), b = 15.115(5), c = 13.233(5) Å, ‐ = 102.21(3)°, V = 2284(1) Å3, Z = 4, and Final R = 0.078.
Synthesis and properties of optically active phosphine‐boranes possessing an l‐menthyloxy group
Authors: Imamoto Tsuneo , Yoshizawa Takeshi , Hirose Koutaro , Wada Yoshiyuki , Masuda Hideki , Yamaguchi Kentaro , Seki Hiroko 
Published: January 2005

Abstract(SP)‐9‐Anthryl(l‐menthyloxy)phenylphosphine‐borane and (SP)‐(1‐l‐menthyloxy)benzo[b]phosphole‐borane were synthesized, and their structures were characterized by X‐ray crystallographic analysis. The latter compound was reduced by lithium naphthalenide at −78°C with cleavage of the PO bond, and the subsequent reaction with electrophiles afforded the corresponding tertiary phosphine‐boranes possessing good to excellent enantiomeric excesses.
A symmetric oxyselenenylation of simple olefins using optically active selenobinaphthyls
Authors: Fujita Ken‐Ichi , Murata Kazuhisa , Iwaoka Michio , Tomoda Shuji 
Published: January 2005

AbstractAsymmetric trans‐addition reactions of simple olefins have been performed by using optically active 2‐selenobinaphthyls 1,2a–g. Introduction of an amide group at the 2′‐position in the binaphthyl skeleton enhances considerably the diastereomeric excess (de) of the asymmetric methoxyselenenylation. In the case of trans‐olefins, introduction of another chiral center in the amide group further enhances the de due to double stereodifferentiation between the (R)‐binaphthyl skeleton and the chiral amide group introduced at the 2′‐position in the binaphthyl skeleton. The use of chiral nucleophiles is also effective to enhance the de for symmetrical cis‐olefins.
Novel syntheses of pyrrolone and pyrrolopyridine derivatives
Authors: Kandeel Zaghloul E. , Hafez Ebtisam A. , Sleim Maghraby A. , Abdelatif Fawi M. , Elnagdi Mohamed H. 
Published: January 2005

Abstract4‐Arylmethylene‐2‐phenyl‐2‐oxazolin‐5‐ones 1a,b reacted with some active methylene reagents to afford pyrrolidine‐3,5‐dione, pyrrolo[2,3‐b]pyridine and pyrrolinone derivatives. The cinnamate ester, obtained from 1a and sodium ethoxide, could be converted into a pyrrolidinone derivative having an active methylene group. This compound coupled with diazonium salts to afford the corresponding azo coupling products.
Complexation of poly‐bis‐(3‐silsesquioxanylpropyl)amino‐sulfoxide and‐sulfone with rare‐earth elements
Authors: Vlasova Natalia N. , Zhila Galina Yu. , Kirillov Anatoly I. , Voronkov Mikhail G. 
Published: January 2005

AbstractPolymers of silsesquioxane structure, poly[bis‐(3‐silsesquioxanyl‐propylamino)]sulfoxide (IV) and ‐sulfone (V) have been prepared and examined as complexation agents toward samarium(III) and thulium(III). Polymer IV was an effective complexation agent toward both of these elements. However, polymer V was an effective complexation agent only toward thulium(III) ions.The selective complexation of polymer V with thulium is not affected by the presence of excess amounts of lanthanum, cerium, neodymium, or samarium salt. This suggests that polymer V may prove to be useful in rare‐earth element (REE) separation and isolation. The selective complexation of V with thulium(III) is also observed in the presence of nickel(II), copper(II), or lead(II) salt.
Preparation of tetra‐n‐butylammonium peroxydisulfate. Novel tetrahydrofuranylation [1] and tetrahydropyranylation of alcohols
Authors: Choi Hyun Chul , Jung Jae Chul , Cho Kyu Ii , Kim Yong Hae 
Published: January 2005

AbstractTetra‐n‐butylammonium peroxydisulfate (Bu4N+ −OS(O2)O–O(O2)SO− +NBu4: (TBA)2S2O8) has been successfully prepared and turned out to be a useful source of the tetra‐n‐butylammonium sulfate radical in organic solvents. Primary, secondary, and tertiary alcohols containing functional groups, such as benzylic, allylic, and sulfide, reacted with tetrahydrofuran or tetrahydropyran in the presence of (TBA)2S2O8 to give the corresponding 2‐tetrahydrofuranyl‐ or 2‐tetrahydropyranyl‐ether in excellent yields under nearly neutral conditions.
1, 2λ5‐azaphosphinines and a new 1λ5, 3λ5‐. Diphosphinine
Authors: Fluck Ekkehard , Rosche Fred , Heckmann Gernot , Weller Frank 
Published: January 2005

AbstractThe 1,2‐azaphosphinine, 9, and the 1,3‐diphosphinine, 10, can be isolated from a mixture resulting from the reaction of 1,1,3,3‐tetrakis(dimethylamino)‐1λ5,3λ5‐diphosphete, 1, and ethyl isothiocyanate. The reaction of 1 with phenyl isothiocyanate yields the 1,2‐azaphosphinine, 16. Mechanisms for the formation of the compounds 9, 10, and 16 are suggested. The properties, the NMR, mass, and IR spectra, and the molecular and crystal structures of 9 and 10 are described and discussed.
The reactions of tetrakis(triphenylphosphine)platinum and ‐palladium with selenium: X‐Ray crystal structure of [Pt(Se2CH2)(PPh3)2]
Authors: Khanna Pawan K. , Morley Christopher P. , Hursthouse Michael B. , Malik K. M. Abdul , Howarth Oliver W. 
Published: January 2005

AbstractTreatment of tetrakis(triphenylphosphine)platinum with elemental selenium (red or vitreous) in toluene solution under reflux yields an insoluble solid. This dissolves in dichloromethane with reaction, eventually to form a 1 : 1 mixture of [PtCl2(PPh3)2] and the new compound [Pt(Se2CH2)(PPh3)2], which has been characterized by multinuclear NMR spectroscopy and X‐ray crystallography. Under the same conditions, tetrakis(triphenylphosphine)‐palladium yields only decomposition products. © John Wiley & Sons, Inc.
Studies with polyfunctionally substituted heteroaromatics: New routes for the synthesis of polyfunctionally substituted pyridines and 1,2,4‐triazolo[1,5‐a]pyridines
Authors: Al‐Omran Fatima , Khalik Mervat Mohamed Abdel , Elnagdi Mohamed Hilmy 
Published: January 2005

AbstractThe 1‐substituted ethylidenemalononitriles 1a–c condensed with triethyl orthoformate in refluxing acetic anhydride to yield the dienes 2a–c. On the other hand, a mixture of N,N‐dimethylformamide and triethyl orthoformate condensed with 1a–d to yield the N,N‐dimethylaminopentadienonitriles 2d–g. The pentadienonitriles 2d–g were also formed from the reaction of 1a–d with dimethylformamide dimethylacetal in refluxing acetic acid. When compounds 1a–c were treated with dimethylformamide dimethylacetal in refluxing p‐xylene, a mixture of 3,4 and 2e–g was formed.The reaction of 2a,b with hydrazine hydrate afforded the N‐amino‐2‐iminopyridines 5a,b. These were converted into the triazolo[1,5‐a]pyridines 8a–d on treatment with benzoyl chloride and with dimethylformamide dimethylacetal. On the other hand, the reaction of 2c with hydrazine hydrate afforded the pyrazolo[3,4‐b]pyridine 7c. Treatment of 2a,c or 2e,g with cyanoethanoic hydrazide afforded the N‐(cyanoacetamido)pyridines 9a,b. The dienes 2d,f,g afforded the pyridones 11a–c on treatment with acetic acid and hydrochloric acid mixture. Compounds 11b,c were also formed on treatment of 2b,c with acetic acid hydrochloric acid mixture. The reaction of 2d,g with ethanolic sodium ethoxide gave the ethoxypyridines 13a,b.
The structure and energies of some unsaturated four‐membered ring carbocycles
Authors: Allinger N. L. , Yuh Y. , Sprague J. T. 
Published: January 2005

AbstractA number of cyclobutane derivatives containing one or more double bonds in endo‐ or exocyclic positions have been studied by the molecular mechanics method within the context of the MM2 force field. Generally speaking, the structures and energies of these compounds are well calculated in cases in which they are known experimentally and are predicted in others. Examples are shown of the use of the moments of inertia of molecules, which are known from microwave studies, in conjunction with molecular mechanics calculations to yield better structures than could be obtained by either method alone. Compounds examined include cyclobutene, methylenecyclobutane, Dewar benzene, and related compounds.
Metal–metal bond energies in Mo2, Mo2Cl, and Mo2(O2CH)4
Authors: Norman Joe G. , Ryan P. Barry 
Published: January 2005

AbstractPrevious attempts to determine the strengths of multiple metal‐metal bonds are reviewed. Estimates of 73 and 97 kcal/mole for the MoMo bond energies in Mo2Cl and Mo2(O2CH)4, respectively, are obtained by combining the known experimental bond energy in Mo2 (96.5 ± 5 kcal/mole) with the results of SCF‐Xα‐SW calculations on Mo2, Mo2Cl, and Mo2(O2CH)4. Possible errors in the estimates are discussed. It is noted that the quadruple bonds in the complexes are predicted stronger per component than the sextuple bond in the diatomic.
A systematic CI procedure with modified virtual orbitals
Authors: Cooper Ian L. , Pounder Christopher N. M. 
Published: January 2005

AbstractThe use of modified virtual orbitals is studied in a systematic conventional CI procedure which offers considerable potential in regard to convergence and extension to larger systems. The method is applied to the HCN molecule by using 37 basis functions, and analysis of energy expectation values, together with the one‐electron density, yields some insight into the physical content of CI wavefunctions.
Atomic Xα calculations based on EHFS(α) = Eexp
Authors: Tseng T. J. , Hong S. H. , Whitehead M. A. 
Published: January 2005

AbstractThe total energies and one‐electron energies for first‐ and second‐row atoms were calculated by using the Hartree–Fock and the Hartree–Fock‐Slater Hamiltonian with Xα orbitals, ui(αexp); α was parametrized from EHFS(αexp) = Eexp. The EHF(αexp) total energies are always higher than the Hartree–Fock energies for the atoms. The relation of the calculated ionization potential to the experimental ionization potential depends on the α used to define ui(α), αexp, or αHF.
Theoretical development of a Gaussian potential function in the description of the radial portion of isotropic bending vibrations
Authors: Lieb S. G. , Perry W. L. , Bevan J. W. 
Published: January 2005

AbstractAnalysis of a Gaussian potential function suitable for modeling degenerate bending vibrations in weakly bound molecular complexes is presented. Approximate eigenvalues and eigenvectors are obtained by application of perturbation theory. Comparison to the “exact” eigenvalues obtained via a numerical solution shows that the first‐ and higher‐order perturbation corrections are consistent with variational principles.
Initial conformations of macrocyclic compounds with rotational symmetry generated from a molecular fragment
Authors: Felder Clifford E. , Shanzer Abraham , Lifson Shneior 
Published: January 2005

AbstractAn algorithm is described for generating atomic Cartesian coordinates of conformations of macrocyclic molecules possessing exact rotational or rotation‐reflection symmetries. A fragment representing the asymmetric unit of the molecule is suitably oriented in space, and then a symmetry operator is applied to generate the initial coordinates of the molecule. An empirical force field of interatomic interactions is used to generate equilibrium conformations. Results of calculations performed on two cyclic polylactones and one crown ether using this approach are given. They reveal that symmetric conformations of these molecules are often preferred. Since the latter conformations are probably responsible for the specialized properties of these molecules, this method should facilitate doing theoretical studies on these kinds of compounds.
Optimized method for the evaluation of the convolutionally distorted decay curves
Authors: Szöke J. 
Published: January 2005

AbstractA nonlinear least squares procedure based on the Meiron method is described for the evaluation of the convolutionally distorted decay curves consisting of exponentials. Most of the special procedures are well known and the selected ones proved to be the most effective. Some new procedures are introduced to facilitate the evaluation work and literature data are analyzed as an example.
The ellipsoid algorithm as a method for the determination of polypeptide conformations from experimental distance constraints and energy minimization
Authors: Billeter M. , Havel T. F. , Wüthrich K. 
Published: January 2005

AbstractA new method for constrained nonlinear optimization known as the ellipsoid algorithm is evaluated as a means of determining and refining the conformations of peptides. Advantages of the ellipsoid algorithm over conventional optimization methods include that it avoids many local minima that other methods would be trapped by, and that it is sometimes able to find optimum solutions in which the constraints are satisfied exactly. The dihedral angles about single bonds were used as variables to keep the dimensionality low (the rate of convergence decreases rapidly with increasing dimensionality of the problem). The method is evaluated on problems involving distance constraints, and for minimization of conformational energy functions. In an initial application, conformations consistent with an experimental set of NMR distance constraints were obtained in a problem involving 48 variable dihedral angles.
An objective computer‐oriented method for the calculation of formation constants from the formation function. A weighted least‐squares curve fitting
Authors: Sidrak Yousry L. , Aboul‐Seoud A. 
Published: January 2005

AbstractA computer program has been developed that calculates, using the weighted least‐squares technique, the overall formation constants, Bi, of mononuclear complexes, the standard deviations of Bi, SDVi, and an estimate of goodness of fit, Goodness‐of‐Fit Parameter (GOFP), given a set of average ligand numbers, VNj, the corresponding free ligand concentrations, VAj, and an error parameter P. The formation function used is ∑(VNj – i) · (Bi) · (VAj)i = 0 where i ranges from O to n with a maximum of 10 and j ranges from O to l with a maximum of 40. The Bi and (Bi – SDVi) must be positive and GOFP must be either unity or as close to unity as possible. An option is available that allows the computation of P, if it is not provided, so that GOFP is equal or very close to unity. The method has been applied to the formation of the complexes Cadmium‐Imidazole, Cobalt(II)‐Bis(2‐Quinaldylphenyl Ketone), Copper‐Ammonia, Silver‐4‐Aminobutan‐1‐ol Nitrate, and Copper(II)‐Bis(2‐Quinaldylphenyl Ketone). The results are quite satisfactory and reliable as compared with other computational techniques. Input data and results for the five complexes mentioned are shown.
Basis sets for molecular interactions. 2. Application to H3NHF, H3NHOH, H2OHF, (NH3)2, and H3CHOH2
Authors: Latajka Zdzislaw , Scheiner Steve 
Published: January 2005

AbstractModifications of the standard 6‐31G** basis set as recommended in the accompanying paper are found to markedly lower the basis set superposition error (BSSE) in the title complexes, in contrast to enlargement to a triple‐ζ scheme or by addition of a diffuse sp shell or a second set of d‐functions without prior optimization, all of which lead to BSSE increase. After appropriate correction for correlation and superposition effects, all basis sets (with the exception of the standard 6‐31G** and 6‐311G** with their very large BSSE) predict the cyclic geometry of NH3 dimer to be more stable than the linear arrangement. Correlation and BSSE can shift the equilibrium intermolecular distance in H3CH‐OH2 by up to 0.4 Å. Failure to correct for superposition error leads to a drastic exaggeration of both the SCF and MP2 components of the interaction energy in this complex. Much better estimates are furnished by our recommended basis sets with their smaller superposition errors.
Two approaches to the calculation of molecular resonance states: Solution of scattering equations and matrix diagonalization
Authors: Basilevsky M. V. , Ryaboy V. M. 
Published: January 2005

AbstractWe have analyzed two approaches to reproduce the resonance expansion of the scattering matrix appropriate for the calculation of molecular resonance states. The first is based on the resonance theory of Siegert‐Humblet‐Rosenfeld (SHR) and the second on the Fano‐Feshbach formalism. The direct method of calculating the resonance expansion characteristics, devised on the basis of the SHR theory, makes it possible to obtain the energies and partial widths (detailed decay rate constants) of resonances. The Fano‐Feshbach formalism, on the other hand, elucidates the resonance state as a concept and facilitates the interpretation of calculation results. The use of computational methods is illustrated by the study of the decay of a model triatomic system and of gas‐phase nucleophilic substitution reactions. Used in the latter case is the division of all degrees of freedom of the reacting system into the adiabatic and dynamic ones along with an algorithm of inclusion of the restricted dynamical treatment in the calculation of reaction rate constants.
The inverse problem of isomer enumeration
Authors: Hässelbarth Werner 
Published: January 2005

AbstractThe present article addresses the problem of identifying the structure of a parent compound through its chemical fingerprints such as the various numbers of isomeric substitution patterns, along the lines of Kekulé when he arrived at his benzene formula. In a pioneering paper (1929), Lunn and Senior laid out the conceptual framework for the permutation group description of substitution isomerism. It remained, however, for Pólya's celebrated contribution (1937) to initiate the actual mathematical realization of their vision. Pólya supplied the tools for solving the isomer enumeration problem: given a (symmetrical) parent compound, enumerate its spectrum of substitution patterns. The converse problem, though ranked the more interesting one by Lunn & Senior, hardly received any mathematical attention. The present article offers a complete and effective solution.