bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pyryliumverbindungen. 30. C‐Alkylierung von 1,3,5‐Triaryl‐penten‐1,5‐dion‐Enolaten: Ein einfacher Zugang zu 3‐alkylsubstituierten 2,4,6‐Triaryl‐pyryliumsalzen
Authors: Fischer Gerhard W. 
Published: January 2005

Pyrylium Compounds. 30. C‐Alkylation of 1,3,5‐Triaryl‐pentene‐1,5‐dione Enolates: A Simple Approach to 3‐Alkylsubstituted 2,4,6‐Triarylpyrylium Salts1,3,5‐Triaryl‐pentene‐1,5‐dione enolates (10), obtainable in crystalline form from 2,4,6‐triarylpyrylium pseudobases (9) and sodium methoxide in benzene/ether, react in dipolar aprotonic solvents (e.g. DMSO, DMF) with various types of alkyl iodides to give C‐alkylation products (11) which afford 3‐substituted 2,4,6‐triarylpyrylium salts (12) on treatment with perchloric acid. This reaction sequence proved to be a convenient synthetic route to pyrylium salts (12) having 3‐oriented substituents such as normal or branched alkyl groups CnH2n+1 (e.g.n = 1–5), isotopically modified alkyl groups (e.g. C[2H3], C2[2H5]), allyl type substituents (e.g. CH2CHCH2, MeCHCHCH2, CH2, CH2CMeCH2) or benzyl groups (e. g. PhCH2, 4‐BrC6H4CH2). Bifunctional alkylating agents (e.g. 1,4‐diiodobutane, o‐xylylenediiodide) resulted in a novel type of bispyrylium salts (14) with 3,3′‐linkage. The pyrylium salts obtained were characterized by their 1H‐n.m.r. and u.v. spectra as well as, in most cases, by transformation into the corresponding pyridine derivatives (13) and bispyridines (15) respectively.
Zur Interpretation relativer Bildungskonstanten von Komplexen mit Lanthanoiden NMR‐Verschiebungsreagenzien
Authors: Doerffel K. , Peters K. , Radeglia R. 
Published: January 2005

On the Interpretation of Relative Binding Constants of Complexes with Lanthanide N.M.R. Shift ReagentsThe determination of relative complex binding constants of lanthanide n.m.r. shift reagents (LSR) with organic molecules are based on the assumption that in all cases 1:1 complexes exist. A new interpretation of relative binding constants is given which is applicable also to 1:2 complexes. The new defined constant K* describes the relative tendency of the substrate under consideration to form LSR complexes.Using this method it is shown that Eu(fod)3 and Pr(fod)3 form other complexes than that of the 1 : 1 type.The K* of benzaldehyde‐LSR complexes correlate linearly with the Hammett substituent parameters.The occurrence of other than 1:1 associates in the complex formation of para‐substituted benzaldehydes with Eu(fod)3 and Pr(fod)3, respectively, could be shown; so we used the new model for these systems. The lg K* of the benzaldehydes in its reaction with the mentioned LSR, as well as with Eu(dpm)3, correlate linearly to the Hammett parameter of the para‐substituents.
Reinvestigation of Thesing's synthesis of 2‐pyridones using 1‐(methylthio‐thiocarbonylmethyl)pyridinium iodide
Authors: Alvarez‐Builla Julio , Benito Juan Lopez , Quintanilla Ma Gloria 
Published: January 2005

AbstractStarting from 1‐(methylthiocarbonylmethyl)pyridinium iodide 1, several attemps were made to prepare 4,6‐diaryl‐2‐pyridothiones. Synthesis of thioamides 2–10 was produced easily and with high yield, but thioamide behaves as a bad stabylising group. A modified method using a mixture of 1, compounds of the type RNH2 and the corresponding chalcone, produced 2‐pyridothiones only when RH, and the compounds where isolated in the oxidised dithioform.Other reactions gave pyridinium salts, or 1,2‐azoles, with no intervention of 1 in the process.
Acetals and Ethers. XVIII. Reaction products of prop‐2‐enal and but‐2‐enal with mixture: n‐Aliphatic alcohol and ethylene glycol
Authors: Piasecki Andrzej 
Published: January 2005

AbstractThe direct condensation reaction of prop‐2‐enal or but‐2‐enal with mixture of n‐aliphatic alcohol and ethylene glycol, in the presence of p‐toluenesulphonic acid as catalyst, leads to a complex mixture of saturated, unsaturated, cyclic and linear acetals, moreover, 2‐(2‐alkoxy‐alkyl)‐1,3‐dioxolanes are the main reaction products. The detailed investigations for n‐butanol showed that unsaturated cyclic acetals: 2‐vinyl‐1,2‐dioxolane 1a or 2‐(1‐propenyl)‐1,3‐dioxolane 1b, as well as unsaturated linear acetals: 1,1‐dibutoxy‐prop‐2‐en 2a or 1,1‐dibutoxy‐but‐2‐en 2b are intermediate reaction products. Additionally, it was found in final products presence of eight by‐products: 5‐butoxy‐4a or 5‐butoxy‐7‐methyl‐1,4‐dioxepane 4b, 1,1,3‐tributoxypropane 5a or 1,1,3‐tributoxybutane 5b, 2‐[2‐(2‐hydroxyethoxy)ethyl]‐6a or 2‐[2‐(2‐hydroxyethoxy)propyl]‐1,3‐dioxolane 6b, 5‐(2‐hydroxyethoxy)‐7‐methyl‐1,4‐dioxepane 7b, 1,3‐dibutoxy‐1‐(2‐hydroxyethoxy)‐propane 8a or 1,3‐dibutoxy‐1‐(2‐hydroxyethoxy)‐butane 8b, 1,1‐dibutoxy‐3‐(2‐hydroxyethoxy)‐propane 9a or 1,1‐dibutoxy‐3‐(2‐hydroxyethoxy)‐butane 9b, 3‐butoxy‐1,1‐bis‐(2‐hydroxyethoxy)‐propane 10a or 3‐butoxy‐1,1‐bis‐(2‐hydroxyethoxy)‐butane 10b, and 1‐butoxy‐1,3‐bis‐(2‐hydroxyethoxy)‐propane 11a or 1‐butoxy‐1,3‐bis‐(2‐hydroxyethoxy)‐butane 11b, respectively.
Elektrochemie organischer Kationen. IV. Untersuchungen zur kathodischen Dimerisierung alkylsubstituierter Pyridiniumionen und zum Reaktionsverhalten dimerer Dihydropyridine
Authors: Pragst F. , Köppel H. , Walkhoff E. , Boche E. 
Published: January 2005

Electrochemistry of Organic Cations. IV. Investigations on the Cathodic Dimerization of Alkyl Substituted Pyridinium Ions and on the Chemical Behavior of Dimeric DihydropyridinesThe cathodic dimerization of a series of 1,2,4,6‐tetraalkylpyridinium ions 1 in acetonitrile and in alkaline aqueous medium as well as the chemical behavior of the bis‐[1,4‐dihydropyridinyl‐(4)] derivatives 2 obtained were investigated. In protic solvents 2 isomerizes by transformation of one or two α‐methyl groups into methylene groups with simultaneous change of one dihydropyridinyl ring to a tetrahydropyridinyl‐ (3) or to a piperidinyl ring (4). The reaction with carboxylic anhydrides, phenylisocyanate, phenylisothiocyanate or the phenyldiazonium ion occurs at the exocyclic double bond formed by this isomerization and leads to acylmethylen‐, N‐phenylcarbamoylmethylen‐, N‐phenylthiocarbamoylmethylen‐ or phenylazomethylen‐substituted 4.
Über die Produkte der Reaktion von Ethylbromid mit Kaliumhydroxid in wäßrig‐alkoholischen Lösungen und den Verlauf dieser SN2‐Reaktion
Authors: Flint A. , Jansen W. , Peper R. , Fickenfrerichs H. , Beneke A. 
Published: January 2005

About the Products of the Reaction of Ethyl Bromide and Potassium Hydroxide in Aqueous Alcoholic Solutions and the Progress of this SN2 ReactionIn the textbooks of organic and general chemistry the reactions of ethyl bromide or methyl bromide with hydroxide ions in alcoholic or aqueous‐alcoholic solutions are the main examples for the SN2 reaction mechanism first established by INGOLD and HUGHES in 1933–1935.It seems clear that the main product of the reaction between ethyl bromide and potassium hydroxide is ethanol apart from a small proportion of ethene in the competing elimination reaction. But the main product of this reaction in ethanolic or aqueous ethanolic solution is diethyl ether or in methanolic or aqueous methanolic solution methyl ethyl ether. Even in the case of using only water, potassium hydroxide and ethyl bromide one can gain 17% of diethyl ether. Kinetic investigations demonstrate that there is a real equilibrium between ethoxide and hydroxide ions in aqueous ethanolic solution. The equilibrium constant is near 0.5, that means that a mixture of ethanol and water contains a rather high amount of ethoxide ions if potassium hydroxide is dissolved in the solution. On the other hand, in the substitution reaction ethoxide ions react 2.5 times faster than OH⊖ at 20°C and 4.5 times faster at 100°C. Therefore, the main substitution reaction in aqueous ethanolic solution after formation of ethoxide ions according to the equilibrium
equation image
is the reaction to diethyl ether according to
equation image
Action of acrylonitrile on 4‐cyano‐ and 4‐carbethoxy pyridazin‐3(2H)‐ones and their 3‐mercapto derivatives. A novel Synthesis of Pyrano and Thiinopyridazines
Authors: Shams N. A. , Kaddah A. M. , Enayat E. I. , Shalaby Alyaa A. , Youssef A. M. 
Published: January 2005

AbstractReaction of acrylonitrile with 4‐cyano‐5,6‐diphenyl pyridazin‐3(2H)‐one and 3(2H)‐thione derivative (1a, b) at elevated temperature gave 7H‐5‐amino‐6‐cyano‐3,4‐diphenylpyrano and thiino [2,3‐c] pyridazines (2a, b), respectively. However, the reaction of 4‐carbethoxy pyridazine derivatives (1c, d) with the same reagent, under the same conditions afforded 6H, 7H‐6‐cyano‐3,4‐diphenyl‐5‐oxopyrano (3a) and thiino [2,3‐c] pyridazine (3b), respectively. In addition, treatment of (1a, c) and (1b, d) with acrylonitrile ar reflux in alkaline medium give the respective 3‐(2′‐cyanoethyloxo) (7a, c) and 3‐2′‐cyanoethylthio (7b, d) pyridazine derivatives. Prolonged alkaline hydrolysis of either (1a, c) or (7a, c) yielded the same product (8a). Also hydrolysis of (1b, d) and (7b, d) afforded one and the same product (8b). The structures of the products were assigned on the basis of satisfactory analytical and spectroscopic data.
Photochemie diarylsubstituierter 2H‐Tetrazole. XI [1] Sydnone V [2]. Blitzlichtphotolytische Untersuchungen an 2,5‐Diaryl‐2H‐tetrazolen und 3,4‐Diarylsydnonen Absolute Cycloadditionsgeschwindigkeitskonstanten von Diarylnitriliminen an Dipolarophile
Authors: Leihkauf P. , Lohse V. , Csonǵr Ch. , Tomaschewski G. 
Published: January 2005

Photochemistry of Diarylsubstituted 2H‐Tetrazoles, XI and Sydnones. V. Flashphotolytic Investigations with 2,5‐Diaryl‐2H‐tetrazoles and 3,4‐Diarylsydnones. Absolute Rate Constants of Cycloadditionreactions of Diarylnitrile Imines to DipolarophilsThe flash photolysis of 2,5‐Diaryl‐2H‐tetrazoles 1 and 3,4‐Diarylsydnones 2 was investigated. The nitrile imines were detected spectroscopically as short living intermediates. Rate constants of the cycloaddition reaction of nitrile imines and dipolarophiles were determined and the influence of substituents in the dipolarophile as well as in the nitrile imine is discussed. The results agree quite well with SUSTMANN'S theroetical classification of 1,3‐dipolar cycloaddition reactions.
Micellaktivierte Reaktionen I. Micellaktivierte Iodierung und partielle Dehalogenierung von Pyrazolen und 1,2,4‐Triazolen
Authors: Miethchen R. , Randow R. , Listemann R. , Hildebrandt J. , Kohlheim K. 
Published: January 2005

Micelle Activated Reactions I. Micelle Activated Iodination and Partial Dehalogenation of Pyrazoles and 1,2,4‐TriazolesA method is described to iodinate pyrazole, substituted pyrazoles or 1,2,4‐triazole with iodine or iodine chloride in aqueous alkaline in the presence of an anionic surfactant. 4‐Iodo‐(2a), 4‐iodo‐3(5)‐methyl‐ (2b), 3(5),4‐diiodo‐ (3a), 3(5),4‐diiodo‐5(3)‐methyl‐ (3b), and 3,4,5‐triiodo‐pyrazole (3d) as soon as 4‐iodo‐pyrazole‐3(5)‐carboxylic acid (2c), and 3(5)‐iodo‐1,2,4‐triazole (5) were prepared.Anhydrous hydrogen fluoride or triethylamine trishydrofluoride were found to be a suitable agent to effect a regioselective partial dehalogenation of 3b, 3d and 3,5‐dibromo‐1,2,4‐triazole (7). We prepared 3(5)‐iodo‐5(3)‐methyl‐pyrazole (6b), 3,5‐diiodo‐pyrazole (6d) and 3(5)‐bromo‐1,2,4‐triazole (8) on this way.
Präparative Aspekte elektrophiler Dreikomponentenreaktionen mit Alkenen
Authors: Beger J. 
Published: January 2005

Preparative Aspects of Electrophilic Three Component Reactions with AlkenesAdditions of the electrophilic species Hal+, NO+, NO2+, SO3H+, RS+, HO+, RCO+ and others in the presence of a third nucleophilic agent like H2O, ROH, ROR, RCOOH, RCN, RSCN and others to an alkene leads to many kinds of unsymmetrical vicinal bifunctionalized compounds of preparative value.In the combination of alkenes with electrophilic halogen and f. e. water the products are 2‐halohydrines, with alcohols 2‐haloalkylethers, with carboxylic acids or derivatives 2‐haloalkylesters and with nitriles N‐2‐haloalkylamides.The intramolecular combination of double bond and nucleophilic center in this reaction gives a lot of saturated heterocycles with five or six membered rings, for example halolactones, tetrahydrofurans or‐pyrans, the corresponding thia analogues, oxazolines, thiazolines, imidazolines and others. Transannular reactions often occurs with medium membered cyclodienes or ‐oligoenes and results in interesting heterocycles, like f. e. oxa‐, thia‐ or azabicyclo [4.2.1.] or [3.3.1.] alkanes. Scope and limitations of such reactions with alkenes are given with 287 references.
Synthese und Struktur von Imino‐bis[1]benzothiopyrano[4,3‐b: 4,3‐f] [1,5]dithiocinen
Authors: Hambsch Monika , Greif Dieter , Pulst Manfred , Weissenfels Manfred 
Published: January 2005

Synthesis and Structure of Imino‐bis[1]benzothiopyrano[4,3‐b:4,3‐f][1,5]dithiocinesSeveral substituted 3‐Alkyl‐ respectively 3‐Aryl‐aminomethylene‐2H‐[1]benzothiopyran‐4‐thiones undergo a thermal reaction yielding the light yellow title compounds 2. For the mechanism of this reaction we propose a condensation reaction of the starting compounds 1 loosing one molecule of amine in the first step followed by electrocyclisation reactions of the intermediates to products 2. The structure of compounds 2 is elucidated by 1H nmr spectroscopy and also x‐ray analysis in case of compound 2b.
Synthesis of Homochiral Side‐chain Precursors for Modified Vitamin D3 Metabolites
Authors: Schrötter Eberhard , Luong Tran Thanh , Schick Hans 
Published: January 2005

AbstractHomochiral 3‐alkylated (2R,3R)‐ and (2R,3S)‐2,3‐dihydroxyalkyl p‐toluenesulfonates (9 and 10) are essential building blocks for vitamin D3 metabolites with a modified side chain. Nine of these compounds have been prepared starting from (R)‐2,3‐O‐cyclohexylideneglyceraldehyde (1) by addition of alkylmagnesium halides, Jones oxidation of the obtained diastereomeric alcohols 2 and 3 to the corresponding ketones 4, and a second addition of alkylmagnesium halides, followed by hydrolytic removal of the cyclohexylidene group and selective tosylation. The opposite diastereoselectivity of the two Grignard reactions is discussed.
Semiempirische Berechnungen und Synthese substituierter 1,4‐Dihydropyridine
Authors: Geibel Kurt , Strohmer Franz , Hammerschmidt Albert 
Published: January 2005

Semiempirical Calculation and Synthesis of Substituted 1,4‐DihydropyridinesSemiempirical calculations of 1,4‐dihydropyridines (1 – 16) done by the programme AMPAC show good consistence between the calculated and the measured absorption maxima at long wavelength. The presented calculation method can be applied to this class of compounds. Correlations between geometry, substitution, conformation, absorption behavior and limitations of the method are discussed.
Unitary group approach to general system partitioning. I. Calculation of U(n = n1 + n2): U(n1) × u(n2) reduced matrix elements and reduced wigner coefficients
Authors: Gould M. D. , Paldus J. 
Published: January 2005

AbstractThis paper is the first in a series of two directed toward a unitary calculus for group‐function‐type approaches to the many‐electron correlation problem. In this paper we present a complete derivation of the matrix elements of the U(n = n1 + n2) generators, for the representations approapriate to many‐electron systems, in a basis symmetry adapted to the subgroup U(n1) × U(n2). Explicit formulae for the fundamental U(n):U(n1) × U(n2) reduced Wigner coefficients, which are needed for the general multishell problem, are also obtained. The symmetry properties of the reduced Wigner coefficients and reduced matrix elements are investigated, and a suitable phase convention is given.
Ab initio scf and Ci study of the electronic structure of the trichlorine radical
Authors: Sannigrahi A. B. , Peyerimhoff Sigrid D. 
Published: January 2005

AbstractAb initio SCF and CI calculations using a double‐zeta plus polarization basis set have been carried out on the trichlorine radical Cl3 to determine its electronic structure. The minimum in energy is determined for a bent structure at a bond angle of 146° and bond lengths of 2.18 Å (SCF) or 2.22 Å (CI). At linear geometry a 2Πu state is found to be lowest, approximately 7 kcal above the bent minimum, followed by a 2∑g+ state, which is around 4 kcal higher. This situation suggests that already for low quantum numbers a complex vibrational pattern in the Cl3 infrared spectrum is to be expected due to spin‐orbit coupling as well as coupling of electronic, vibrational, and rotational motion.
Nitromethane dimer potential energy surface studies
Authors: Cole Samuel J. , Szalewicz Krzysztof , Bartlett Rodney J. 
Published: January 2005

AbstractThe interaction energy of several conformations of the nitromethane dimer is investigated at the SCF level. The dispersion energy and counterpoise correction are computed for certain relative orientations of the monomers. Fourth‐order many body perturbation theory SDQ‐MBPT(4) energies are reported for selected points. Double zeta and double zeta plus polarization basis sets were used. All calculations were done with the monomer fixed at the isolated monomer geometry. Interaction energies as large as 6 kcal/mol are found at minima of hydrogen bonding orientations.
Graphical unitary group approach to arbitrary spin representations
Authors: Kent R. D. , Schlesinger M. 
Published: January 2005

AbstractA graph theoretic approach to the representation of N particle systems involving arbitrary single‐particle spin is presented. The method is a generalization of the Distinct Row Table (DRT) technique employed by Shavitt in developing the graphical unitary group approach (GUGA) to electronic spin‐orbitals. A detailed analysis of the DRT and GUGA representations is presented based on several theoretical considerations and computer‐tested implementations. The use of the representation to establish rules concerning the evaluation of the matrix elements of the group generators is also discussed.
A theoretical study of N‐nitrosamine metabolites: Possible alkylating species in carcinogenesis by N,N'‐dimethyl nitrosamine
Authors: Thomson Colin , Reynolds Christopher A. 
Published: January 2005

AbstractThe results of ab initio calculations using a 4–21G basis set are reported for various possible metabolites of N,N'‐dimethylnitrosamine. The relevance of these results to the nature of the alkylating agent is discussed. Although the calculations widen the range of possible alkylating agents that need to be considered, the diazonium ion appears to be the most likely candidate.
From determinants to spin eigenfunctions—a simple algorithm
Authors: Duch Włodzisław 
Published: January 2005

AbstractCalculation of blocks of matrix elements between determinants associated with two fixed orbital configurations is very easy. A simple method to obtain the whole blocks and then transform them to the spinadapted basis is described. The method is suitable for many‐particle operators, the number of operations to obtain matrix elements being independent of the number of orbitals or electrons. Some applications of the proposed algorithm, and possible extensions to eigenfunctions of Ľ2 and other operators, are discussed.
Atomic Thomas‐Fermi theory and electron subshell filling
Authors: Ten Hoor Marten J. 
Published: January 2005

AbstractIn previous work on electron subshell filling, the existence condition of the integrals involved has not been taken into proper account. As a result, part of the calculated subshell occupation numbers is meaningless.In Theis' theory [9] the average number of electrons in a subshell is calculated as the difference between two integrals. With each of these integrals an existence condition is associated. Because of this, the number of electrons with angular momentum quantum number l can only be calculated for atoms of which the Z value is (much) larger than the corresponding empirical first‐appearance Z value. Thus, the range of Z for which such numbers can be calculated, is restricted considerably, especially for larger values of l.Results obtained from a normalized version of Mason's approximation [13] to the exact Thomas‐Fermi function, have been compared with a least‐squares fit of the empirical subshell occupation numbers, and these are found to be as good as one may expect from a statistical theory.A lower bound to each of the empirical first‐appearance Z values has been calculated. The results agree well with those reported in other work.
Geometrical energy derivative evaluation with MRCI wave functions
Authors: Shepard Ron 
Published: January 2005

AbstractThe theory of MCSCF and CI energy derivatives with respect to geometrical variations is briefly reviewed with special attention given to the MCSCF and MRCI energy gradients. A computational procedure is proposed for MRCI energy gradients that does not require the solution to any “coupled‐perturbed MCSCF” equations, it does not require any expensive direct‐CI matrix‐vector products involving derivative integrals, and it does not require any derivative integrals to be transformed from the AO basis to the MO basis. An additional feature is that it does not require any changes to existing MCSCF gradient evaluation programs in order to compute MRCI gradients. The only difference in the two cases is the exact nature of the data passed to the gradient evaluation program from the previous steps in the computational procedure. The additional effort required to compute the entire MRCI energy gradient vector is approximately that required for one additional iteration of the MRCI diagonalization procedure and for one additional MCSCF iteration. For large scale MRCI wave functions, the MRCI energy gradient evaluation should only require about 10% of the effort of computing the wave function itself. This computational procedure removes a major computational botleneck of potential energy surface evaluation.
Correlation balance in basis sets for electronic structure calculations
Authors: Gordon Mark S. , Truhlar Donald G. 
Published: January 2005

AbstractThe balanced addition of polarization functions to the 6–31G and 6–311G basis sets for correlated wave functions is evaluated using bond energy predictions at the MP2 and full MP4 levels as a measure of correlation‐balanced basis sets. The homolytic dissociations of the XH bonds in H2, CH4, NH3, H2O, and HF and the XY bonds in C2H6, NH2NH2, HOOH, and CH3OH are used as the basis for the evaluation. It is found that correlation balance is achieved for HH, XH, and XY bonds, particularly at the MP2 level, only if at least as many polarization sets, and sometimes more, are added to the hydrogens as are added to the heavy atoms.