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1.
Synthesis of Highly Substituted γ‐Butyrolactones by a Gold‐Catalyzed Cascade Reaction of Benzyl Esters 下载免费PDF全文
Maria Camila Blanco Jaimes Alexander Ahrens Daniel Pflästerer Dr. Matthias Rudolph Prof. Dr. A. Stephen K. Hashmi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):427-433
Easily accessible benzylic esters of 3‐butynoic acids in a gold‐catalyzed cyclization/rearrangement cascade reaction provided 3‐propargyl γ‐butyrolactones with the alkene and the carbonyl group not being conjugated. Crossover experiments showed that the formation of the new C?C bond is an intermolecular process. Initially propargylic–benzylic esters were used, but alkyl‐substituted benzylic esters worked equally well. In the case of the propargylic–benzylic products, a simple treatment of the products with aluminum oxide initiated a twofold tautomerization to the allenyl‐substituted γ‐butyrolactones with conjugation of the carbonyl group, the olefin, and the allene. The synthetic sequence can be conducted stepwise or as a one‐pot cascade reaction with similar yields. Even in the presence of the gold catalyst the new allene remains intact. 相似文献
2.
In this article, we present results of an empirical study with 500 German students of grades 7 and 8. The study focussed on students' mathematics achievement and their interest in mathematics as well as on the relation between these two constructs. In particular, the results show that the development of an individual student's achievement between grade 7 and grade 8 depends on the achievement level of the specific classroom and therefore on the specific mathematics instruction Interest in mathematics could be regarded a predictor for mathematics achievement Moreover, our findings suggest that the students show hardly any fear of mathematics independent of their achievement level. 相似文献
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From the highly refined proton-NMR spectra of monocyclic and bicyclic aminopolyethers, signal shifts have been observed which indicate conformation changes in the ligand moiety. Their dependence on solvent, coordinated cation and anion is discussed, and an interpretation of the spectra is put forward on the basis of dynamic symmetry patterns. 相似文献
7.
F. Gutbrod G. Kramer G. Rudolph G. Schierholz 《Zeitschrift fur Physik C Particles and Fields》1987,35(4):543-549
TheO(α s 2 ) QCD corrections to the thrust distribution for three-jet production ine + e ? annihilation are found to depend on the algorithm for recombining four partons into three jets. Several recombination schemes are discussed and results are compared. Results of the recombination approach are compared also to recent direct calculations of three-jet thrust distributions. The importance of terms proportional to jet resolution parameters is stressed. 相似文献
8.
H. D. Rudolph 《Structural chemistry》1991,2(6):581-588
This work investigates and enumerates the types of molecular structure that can, in principle, be obtained when moments of inertia, planar moments, or rotational constants or different forms of their isotopic differences are least-squares fitted to the respective experimental ground state values. Ther
0-structure, ther
0-derived pseudo-Kraitchman structuresr
I andr
B, and an inequality relation between them are discussed. A least-squares treatment that tries to determine not only the set of structural parameters but also constant, i.e., isotope-independent, rovibrational contributions to the moments of inertia or rotational constants is possible and merits preference. It is shown that the resulting structures are, however, identical with the formerr
orr
B-structures, respectively. 相似文献
9.
Rudolph Willem Ann Delmotte Inge De Borger Monique Biesemans Marcel Gielen Franois Kayser Edward R. T. Tiekink 《Journal of organometallic chemistry》1994,480(1-2):255-259
The synthesis of (Z)-2-methyl-3-triphenylstannyl-3-pentene-2-ol and its characterization by an X-ray diffraction study and multinuclear NMR are reported. The tin atom exhibits a distorted tetrahedral SnC4 geometry with the four Sn---C bond distances experimentally equivalent. The slight distortion from the ideal tetrahedral geometry is because of the presence of a weak intramolecular HO → Sn interaction of 3.012(3) Å which produces a loose four-membered ring. The title compound was characterized in solution by 1H, 13C and 119Sn NMR, and the persistence of the weak intramolecular HO → Sn coordination in solution was revealed by 13C and 119Sn secondary isotope multiplet of partially labelled entities (SIMPLE-NMR) experiments. 相似文献
10.
New Redox Series Based on Transition Metal Complexes of Heterocyclic Arenesulfonylhydrazones Heterocyclic bidentate arenesulfonylhydrazones (2-acetylpyridine-p-toluenesulfonylhydrazone ? APSH? H, 2-acetylquinoline-p-toluenesulfonylhydrazone ? ACSH? H) with transition metal ions afford tetrahedral 1,2-complexes MII(APSH)2 and MII(ACSH)2. In most cases the E-isomers of APSH? and ACSH? are coordinated, five-membered chelate rings are formed with the pyridine and hydrazone nitrogen atoms as donor atoms. In the complexes Zn(APSH)2 and Cu(APSH)2 probably the Z-isomer of APSH? is present with the pyridine and the sulfonylamide nitrogen atoms as a donor set, yielding a six-membered chelate ring. These proposals are based on the magnetic moments, the ligand field spectra, and the binding energies (ESCA). Normally the complexes MII(APSH)2 and MII(ACSH)2 are reduced in two reversible steps. For Fe(APSH)2 and Fe(ACSH)2 a third anodic wave, but for Cu(APSH)2 only one wave is observed. Relations between redox properties and structure of the new complexes are discussed, and the redox series are compared with that of the M(dipy)3n+-type complexes. 相似文献