## Abstract Phenazopyridine hydrochloride (**1**), a drug in clinical use for many decades, and some derivatives were studied by one‐ and two‐dimensional ^1^H, ^13^C and ^15^N NMR methodology. The assignments, combined with DFT calculations, reveal that the preferred protonation site of the drug is
1H, 13C and 15N NMR spectral assignments for new triazapentalene derivatives
✍ Scribed by Pascal Palmas; Coralie Nyffenegger; Eric Pasquinet; Gérald Guillaumet
- Publisher
- John Wiley and Sons
- Year
- 2009
- Tongue
- English
- Weight
- 126 KB
- Volume
- 47
- Category
- Article
- ISSN
- 0749-1581
- DOI
- 10.1002/mrc.2458
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✦ Synopsis
Abstract
Mesomeric heteropentalene betaines are conjugated fused polyheterocyclic structures that represent interesting intermediates for organic synthesis. Five such structures, containing at least four nitrogen atoms and various substituents, have been characterized by ^1^H, ^13^C and ^15^N NMR. We report, apparently for the first time, nitrogen NMR data and coupling information on such systems. Inter‐ring long‐range correlations across five bonds with ^15^N (^5^J~HN~) and up to seven bonds with ^13^C (^6^J~HC~ and ^7^J~HC~) were observed in HSQC experiments. The incorporation of an electron‐withdrawing substituent such as NO~2~ was observed to cause an increase in the magnitude of the remote couplings and deshielding of nearby protons, carbons and on all nitrogen atoms of the structure, including remote ones situated on other cycles. Copyright © 2009 John Wiley & Sons, Ltd.
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