NMR spectra of pyrimidines. Effect of substituents on the chemical shift of the protons of the amino group of p-substituted 2- and 5-aminopyridines and anilines

1979 ◽  
Vol 15 (12) ◽  
pp. 1357-1361
Author(s):  
O. P. Shkurko ◽  
V. P. Mamaev
1997 ◽  
Vol 62 (8) ◽  
pp. 1169-1176 ◽  
Author(s):  
Antonín Lyčka ◽  
Jaroslav Holeček ◽  
David Micák

The 119Sn, 13C and 1H NMR spectra of tris(1-butyl)stannyl D-glucuronate have been measured in hexadeuteriodimethyl sulfoxide, tetradeuteriomethanol and deuteriochloroform. The chemical shift values have been assigned unambiguously with the help of H,H-COSY, TOCSY, H,C-COSY and 1H-13C HMQC-RELAY. From the analysis of parameters of 119Sn, 13C and 1H NMR spectra of the title compound and their comparison with the corresponding spectra of tris(1-butyl)stannyl acetate and other carboxylates it follows that in solutions of non-coordinating solvents (deuteriochloroform) the title compound is present in the form of more or less isolated individual molecules with pseudotetrahedral environment around the central tin atom and with monodentately bound carboxylic group. The interaction of tin atom with oxygen atoms of carbonyl group and hydroxyl groups of the saccharide residue - if they are present at all - are very weak. In solutions in coordinating solvents (hexadeuteriodimethyl sulfoxide or tetradeuteriomethanol), the title compound forms complexes with one molecule of the solvent. Particles of these complexes have a shape of trigonal bipyramid with the 1-butyl substituents in equatorial plane and the oxygen atoms of monodentate carboxylic group and coordinating solvent in axial positions.


Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 916 ◽  
Author(s):  
Wu Lan ◽  
Fengxia Yue ◽  
Jorge Rencoret ◽  
José del Río ◽  
Wout Boerjan ◽  
...  

Tricin [5,7-dihydroxy-2-(4-hydroxy-3,5-dimethoxyphenyl)-4H-chromen-4-one] is a flavone that has been found to be incorporated in grass lignin polymers via 4′–O–β coupling. Herein, we investigated the tricin-lignin structure using nuclear magnetic resonance (NMR) methods by comparing the 1H–13C heteronuclear correlation (HSQC) NMR spectra of the isolated lignin with a series of dimeric and trimeric tricin-4′–O–β-ether model compounds. Results showed that the tricin moiety significantly affects the chemical shift of the Cβ/Hβ of 4′–O–β unit, producing peaks at around δC/δH 82.5–83.5/4.15–4.45, that differ from the Cβ/Hβ correlations from normal 4–O–β units formed solely by monolignols, and that have to date been unassigned.


1998 ◽  
Vol 53 (11) ◽  
pp. 1285-1293 ◽  
Author(s):  
Skeletal Rearrangements ◽  
Ylidediylphosphane Tetramer ◽  
Hans-Peter Schrödel ◽  
Alfred Schmidpeter ◽  
Heinrich Nöth

Condensation of the bis(trimethylsilyl)ylide Ph3PC(SiMe3)2 with PX3 (X = Cl, Br) yields the ionic tetramers 4a,b of ylidediyl-halophosphanes. Their cations (Ph3PC)4P4X3+ possess a tetraphosphabicyclo[2.2.2]octane (or tetraphospha-barrelane) skeleton ([AC]3BD spin system in 31P NMR spectra). Reaction of 4a with AlCl3 or GaCl3 converts the singly charged cation into the tetracation (Ph3PC)4P44+ having a cubane structure ([AB]4 spin system in the 31P NMR spectum). SbCl5 oxidizes 4a to give the dication (Ph3PC)4P4Cl42+ (counter ion: SbCl52-) with the barrelane skeleton either preserved (7) or rearranged into a tetraphospha-bicylco[3.3.0]- octane structure 8. In the latter case the dication contains a central diphosphanedionium bridge. Replacement of a chloro-substituent in 4a by an amino group also gives rise to a further dissociation and a concomitant rearrangement. The resulting dications (Ph3PC)4P4NR2Cl2+ possess a tetraphospha-bicyclo-[3.2.1]octane structure (with eight nonequivalent phosphorus atoms).


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