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31.
James J. Li R. Alan Chrusciel Monica B. Norton David B. Reitz Timothy J. Hagen Sofya Tsymbalov E. Ann Hallinan 《Journal of heterocyclic chemistry》1994,31(6):1689-1696
Lithiation of 8-chlorodibenz[b,f][1,4]oxazepine-10-tert-butylcarbamate ( 1 ) is described. Electrophilic substitution of the resulting N-Boc dibenzoxazepine α- lithioamine 2 with ketones, aldehydes, nitriles, iso-cyanates and imines, followed by an in-situ cyclization, gave fused carbamates 5–26 , fused 2H-imidazol-2-ones 27–29 , fused hydantoins 30–32 , and fused ureas 33–35 , respectively, in 11–66% yield. 相似文献
32.
33.
34.
Jean-Franois Nierengarten Tilo Habicher Roland Kessinger Francesca Cardullo Franois Diederich Volker Gramlich Jean-Paul Gisselbrecht Corinne Boudon Maurice Gross 《Helvetica chimica acta》1997,80(7):2238-2276
The macrocyclization between buckminsterfullerene, C60, and bis-malonate derivatives in double Bingel reaction provides a versatile and simple method for the preparation of covalent bis-adducts of C60 with high regio- and diastereoselectivity. A combination of spectral analysis, stereochemical considerations, and X-ray crystallography (Fig. 2) revealed that out of the possible in-in, in-out, and out-out stereoisomers, the reaction of bis-malonates linked by o-, m-, or p-xylylene tethers afforded only the out-out ones (Scheme 1). In contrast, the use of larger tethers derived from 1,10-phenanthroline also provided a first example, (±)- 19 (Scheme 2), of an in-out product. Starting from optically pure bis-malonate derivatives, the new bis-functionalization method permitted the diastereoselective preparation of optically active fullerene derivatives (Schemes 4 and 5) and, ultimately, the enantioselective preparation (enantiomeric excess ee > 97%) of optically active cis-3 bis-adducts whose chirality results exclusively from the addition pattern (Fig. 6). The macrocyclic fixation of a bis-malonate with an optically active, 9,9′-spirobi[9H-fluorene]-derived tether to C60 under generation of 24 and ent- 24 with an achiral addition pattern (Scheme 4) was found to induce dramatic changes in the chiroptical properties of the tether chromophore such as strong enhancement and reversal of sign of the Cotton effects in the circular dichroism (CD) spectra (Figs. 4 and 5). By the same method, the functionafized bis-adducts 50 and 51 (Schemes 10 and 11) were prepared as initiator cores for the synthesis of the fullerene dendrimers 62 , 63 , and 66 (Schemes 12 and 13) by convergent growth. Finally, the new methodology was extended, to the regio- and diastereoselective construction of higher cyclopropanated adducts. Starting from mono-adduct 71 , a clipping reaction provided exclusively the all-cis-2 tris-adduct (±)- 72 (Scheme 14), whereas the similar reaction of bis-adduct 76 afforded the all-cis-2 tetrakis-adduct 77 (Scheme 15). Electrochemical investigations by steady-state voltammetry (Table 2) in CH2Cl2 (+0.1M Bu4NPF6) showed that all macroeyciic bis(methano)fullerenes underwent multiple reduction steps, and that regioisomerism was not much influencing the redox potentials, All cis-2 bis-adducts gave an instable dianion which decomposed during the electrochemical reduction. In CH2Cl2, the redox potential of the fullerene core in dendrimers 62, 63 , and 66 is not affected by differences in size and density of the surrounding poly(ether-amide) dendrons. The all-cis-2 tris- and tetrakis(meihano)fullercnes (±) -72 and 77 , respectively, are reduced at more negative potential than previously reported all-e tris- and tetrakis-adducts with methane bridges that are also located along an equatorial belt. This indicates a larger perturbation of the original fullerene π-chromophore and a larger raise in LUMO energy in the former derivatives. 相似文献
35.
Volker Staemmler 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1997,39(2):121-125
Accurate quantum-chemical ab initio calculations have been performed at the SCF and CEPA (coupled electron pair approximation) levels for the van der Waals interaction in the X 2 Σ + ground state of LiHe. An extended basis set has been used and the counterpoise correction for the basis set superposition error (BSSE) has been applied. The calculated potential energy curve has a very shallow minimum at 11.56 a 0 with a well depth of only 1.49 cm?1. This is too small to allow for a bound vibrational level. The analysis of the results shows that the interaction mainly consists of the Pauli repulsion between Li(1s 22s) and He (1s 2), which is decaying exponentially, and the attractive London dispersion energy. Van der Waals coefficients C6, C8, and C10 have been determined by a least squares fit to the long-range part of the calculated potential curve. 相似文献
36.
Five different structures of CH5
+ and one structure of CH5
– are calculated using a gaussian basis both in the SCF approximation and with the inclusion of electron correlation in the independent electron pair approximation (IEPA). While on SCF level the C
sstructure of CH5
+ has to lowest energy, the energy difference between the C
sand C
2vstructures becomes negligible if correlation is included. In contrast to this the approach of a proton to CH4 at large and intermediate distances is most favorable towards a corner of the CH4 tetrahedron which means a structure. The decomposition of CH5
+ into CH3
+ and H2 requires 20kcal/mol on SCF level and 40 kcal/mol if correlation is included. 相似文献
37.
Pressure-supported packed capillary electrochromatography (CEC) and packed capillary high-performance liquid chromatography (pHPLC) have been coupled on-line to electrospray ionization-mass spectrometry (ESI-MS) and coordination ion spray-mass spectrometry (CIS-MS). Separation of enantiomers of barbiturates and chlorinated alkyl phenoxypropanoates were performed on a permethylated beta-cyclodextrin stationary phase by pressure-supported CEC. For on-line detection with ESI- and CIS-MS, a modified sheath-liquid interface was used. CIS-MS is a universal, novel ionization technique which improves the selectivity as well as the sensitivity. Charged complexes were formed through the addition of central complexing ions such as silver(I), cobalt(II), copper(II), and lithium(I) to the sheath flow. Advantages of CIS-MS detection compared to the ESI-MS mode are discussed. In the CIS-MS mode, increased sensitivity and high selectivity was attained through different possibilities of complexation. The superiority of pressure-supported CEC compared to pHPLC in the hyphenation with CIS-MS is demonstrated. 相似文献
38.
Herwig G. Winkler Hagen T. Spath Prof. Dr. Karl Torkar 《Monatshefte für Chemie / Chemical Monthly》1975,106(2):535-545
The phase diagrams of the systems CsN3/Zn(N3)2 and KN3/Zn(N3)2 have been obtained employing the microscopic technique ofL. Kofler andA. Kofler. Within the system CsN3/Zn(N3)2 three eutectics at 148°C, 142°C, and 210°C were found. Besides Cs2Zn(N3)4, melting incongruently in the interval 153°C to 170°C, there exist two further compounds of the most probable composition Cs3Zn2(N3)7 and CsZn2(N3)5, melting congruently at 170°C and 210°C, resp. In the system KN3/Zn(N3)2 there exist two eutectics at 203°C and 172°C and two compounds, one of them, i.e. K2Zn(N3)4, melting congruently at 206°C, the other one, with composition KZn3(N3)7 or KZn4(N3)9, melting incongruently at 210°C.
Mit 8 Abbildungen
Herrn Professor Dr.Heribert Grubitsch zum 70. Geburtstag gewidmet. 相似文献
Mit 8 Abbildungen
Herrn Professor Dr.Heribert Grubitsch zum 70. Geburtstag gewidmet. 相似文献
39.
Electron-deficient aromatics, such as 2,5-bis(trifluoromethylmercapto)thiophene () or (trifluoromethylmercapto)benzene (), react with F3CSCl in the presence of F3CSO3 as a catalyst to give mainly 3-chloro-2,5-bis(trifluoromethylmercapto)thiophen () and 1-chloro-4- or 2-(trifluoromethylmercapto)benzene (, respectively. This reaction competes with the one expected to result in 2,3,5-tris(trifluoromethylmercapto)thiophene () and 1,4- and 1,2-bis(trifluoromethylmercapto)benzene (,), respectively. Further reactions of deactivated aromatics with Cl3-nFnCSCl show that the chlorine substitution is in general catalysed by strong acids. Reaction mechanisms are proposed for both Substitutions. The Cl3-nFnCS group in aromatics exerts a -M-effect in the case of an attack of a positive ion, e.g. H⊕, the well-known +M-effect in the case of reactions with positively polarized molecules, e.g. CF3Sβ+Clβ-. 相似文献
40.
An iterative procedure is presented which allows for the direct determination of approximate Brueckner orbitals for small atomic and molecular systems. Starting from the Hartree-Fock determinant one first determines pair natural orbitals (PNOs) of independent electron pairs in the HF-field of the remaining electrons. The use of the generalized Brillouin-theorem then leads to an approximate Brueckner orbital for each electron pair. This procedure must be repeated up to self-consistency which is reached generally after 4–5 macroiterations. Applications to the ground state of H2 show how important the use of Brueckner orbitals is to get good expectation values of one-electron operators and the correct asymptotic behaviour of the potential energy curve for large internuclear distances.
Dedicated to the memory of Prof. K. H. Hansen. 相似文献
Zusammenfassung Es wird eine Iterationsmethode beschrieben, die eine direkte Bestimmung genäherter Bruecknerorbitale für kleine atomare und molekulare Systeme gestattet. Ausgehend von der Hartree-Fock-Determinante bestimmt man zunächst Paar-NOs (PNOs) der unabhängigen Elektronenpaare im HF-Feld der übrigen Elektronen des Systems. Mit Hilfe des verallgemeinerten Brillouin-Theorems erhält man dann ein genähertes Bruecknerorbital für jedes Elektronenpaar. Dies Verfahren muß bis zur Selbstkonsistenz wiederholt werden, die man im allgemeinen nach 4–5 solcher Makroiterationen erreicht. Anwendung auf den Grundzustand des H2-Moleküls zeigt, wie wichtig die Benutzung von Bruecknerorbitalen ist, wenn man gute Erwartungswerte von Einelektronenoperatoren und das richtige asymptotische Verhalten der Potentialkurve bei großen Abständen erhalten will.
Résumé On propose un schéma itératif qui permet le calcul direct des orbitales de Brueckner approchées pour les atomes et les petites molécules. Partant du déterminant Hartree-Fock on calcule d'abord les PNO (pair natural orbitals) des paires indépendantes d'électrons dans le champ effectif des autres électrons dans l'approximation Hartree-Fock. Ensuite le théorème de Brillouin généralisé permet de calculer les orbitales de Brueckner approchées pour chaque paire d'electrons. On recommence le calcul des PNO, la self-consistance de cette méthode itérative s'établit en général au bout de 4 ou 5 macroitérations. Les applications à la molécule H2 démontrent que l'utilisation d'orbitales de Brueckner s'impose si l'on s'intéresse à des bonnes valeurs moyennes d'opérateurs monoélectroniques ou au comportement asymptotique correct des courbes de potentiel aux grandes distances.
Dedicated to the memory of Prof. K. H. Hansen. 相似文献