NMR Spectroscopic Experiments (nmr + spectroscopic_experiment)

Distribution by Scientific Domains


Selected Abstracts


Strong Evidence for an Unprecedented Borderline Case of Dissociation and Cycloaddition in Open-Shell 1,3-Dipole Chemistry: Transient Nitrilium Phosphane-Ylide Complex Radical Cations

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2009
Holger Helten
Abstract The reaction of 3-ferrocenyl-substituted 2H -azaphosphirene complexes 1a,c in the presence of substoichiometric amounts of ferrocenium hexafluorophosphate yields 3,5-diferrocenyl-substituted 2H -1,4,2-diazaphosphole complexes 3a,c and difluoro(organo)phosphane complexes 4a,c. The reaction of 1a,c and [FcH]PF6 with cyanoferrocene yields 3a,c in a straightforward way. The molecular structures of 3a,c were unambiguously identified by multinuclear NMR spectroscopic experiments, mass spectrometry, and single-crystal X-ray diffraction studies. DFT calculations on model complexes 1d,m and 3d,m reveal a close similarity of Mo and W complexes (vs. Cr) and a strong influence of the ferrocenyl substituent on the geometry, spin, and charge distribution of reactive intermediates and the reaction course. Strong support for the assumption of a dissociation,cycloaddition reaction sequence leading to 3 and thus a surprising "cannibalistic" reaction was obtained.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


New Triterpenoidal Saponins from Gypsophila repens

HELVETICA CHIMICA ACTA, Issue 2 2007
Mohamed Elbandy
Abstract Six new triterpene glycosides, repensosides A,F (1,6, resp.), were isolated from the roots of Gypsophila repens L. Their structures, established by extensive 1D- and 2D-NMR spectroscopic experiments as well as MS analyses, were found to be based on gypsogenic acid (or gypsogenin) as aglycone, with three to nine branched or unbranched sugar moieties. [source]


Deprotonative Metalation of Substituted Benzenes and Heteroaromatics Using Amino/Alkyl Mixed Lithium,Zinc Combinations

CHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2010
Katia Snégaroff Dr.
Abstract Different homoleptic and heteroleptic lithium,zinc combinations were prepared, and structural elements obtained on the basis of NMR spectroscopic experiments and DFT calculations. In light of their ability to metalate anisole, pathways were proposed to justify the synergy observed for some mixtures. The best basic mixtures were obtained either by combining ZnCl2,TMEDA (TMEDA=N,N,N,,N, -tetramethylethylenediamine) with [Li(tmp)] (tmp=2,2,6,6-tetramethylpiperidino; 3,equiv) or by replacing one of the tmp in the precedent mixture with an alkyl group. The reactivity of the aromatic lithium zincates supposedly formed was next studied, and proved to be substrate-, base-, and electrophile-dependent. The aromatic lithium zincates were finally involved in palladium-catalyzed cross-coupling reactions with aromatic chlorides and bromides. [source]


The synthesis of novel polycyclic heterocyclic ring systems via photocyclization.

JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2000

Photocyclization of 3-chloro- N -(3-phenanthryl)naphtho[1,2- b]thiophene-2-carboxamide (12) furnished only one of the two possible isomers, i.e., naphtho[2,,1,:4,5]thieno[2,3- c]naphtho[1,2- f]quinolin-6(5H)-one (13), which was further elaborated to yield the unsubstituted ring system 7, its triazole 8 and tetrazole 9. The structural confirmation of 7 was accomplished by the total assignment of its 1H and 13C nmr spectra utilizing the concerted two-dimensional nmr spectroscopic experiments. [source]