NMR studies of N-(benzimidazol-2-yl)pyridinium derivatives: QSAR with the anti-leishmanial activity and their carbon-13 NMR chemical shifts

Alcalde, Ermitas; Dinarés, Immaculada; Frigola, Jordi

doi:10.1016/0223-5234(91)90199-w

Cited by 8 publications

(2 citation statements)

References 11 publications

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“…In sharp contrast, very few examples are known to date of conjugated molecules with more than one positive and one negative charge, althoughon the other handcharge-cumulated systems such as poly cationic molecules have attracted considerable attention as novel organic oxidizing agents, precursors of organic radicals, and potential semiconductors . Moreover, there has been renewed interest in the synthesis of betaines with antileishmanial, antiprotozoal, and antitrichomonal activities …”

Section: Introductionmentioning

confidence: 99%

Heteroaromatic Tripoles. 2,6-Bis(hetarenio)pyrimidin-4-olates: Hybrids between Hetarenium Salts and Cross-Conjugated Mesomeric Betaines

Schmidt

Kindermann

1998

J. Org. Chem.

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A novel tandem nucleophilic displacement reaction on tetrachloropyrimidine 7 leads to molecules with two delocalized positive and one delocalized negative charge, which comprise a common π-electron system, plus one external anion. Thus, treatment of 7 with an excess of heteroaromatic nucleophiles such as 4-(dimethylamino)pyridine, 4-(pyrrolidin-1-yl)pyridine, and 1-methylimidazole, respectively, followed by the addition of water formed the tripolar bis(hetarenio)pyrimidin-4-olates 8, 9, and 10. Addition of anhydrous alcohols furnished the O-alkylated dicationic species 11-16. We contrast the spectroscopic features of the monocationic 8-10 and the dicationic 11-16 and performed a conformational study (PM3). The HOMO/LUMO profile was calculated to evaluate our classification of 8-10 as CCMB derivatives.

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Section: Introductionmentioning

confidence: 99%

Heteroaromatic Tripoles. 2,6-Bis(hetarenio)pyrimidin-4-olates: Hybrids between Hetarenium Salts and Cross-Conjugated Mesomeric Betaines

Schmidt

Kindermann

1998

J. Org. Chem.

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“…Although much work has been concentrated upon the search for novel prodrug derivatives of modified pyrimidine nucleobases 5 including 5-fluorouracil (5-FU), widely used as an antitumor agent, not much interest has been developed in the synthesis of new highly dipolar pyrimidines as potential biologically active compounds. However, the activities of known positively charged and betainic heterocyclic systems that are hetarenium-substituted cover the range from antitrichomonal, antileishmanial, amebicidal, and antiprotozoal agents, acetylcholin-esterase reactivators, and herbicides to semiconductors . Furthermore, the chemistry and widespread use of uracils as active principles have recently been reviewed …”

mentioning

confidence: 99%

Charged and Betainic Nucleobases. On Syntheses and Properties of First Mesomeric Uracilylbetaines, Uracilates, and Novel Uracilium Salts

Schmidt

Kindermann

1997

J. Org. Chem.

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Nucleophilic heteroaromatic substitution of DMAP and 1-methylimidazole on the 6-chlorouracil 1 gave the uracilyl hetarenium salts 2 and 4, respectively. Depending on the nucleophile, the substitution could be catalyzed by interception of the leaving group either with sodium tetraphenylborate or with antimony pentachloride in a non-coordinating solvent. Catalysis with other Lewis acids failed due to the formation of stable coordination compounds 3. Surprisingly, Finkelsteintype reaction conditions provide an efficient approach to the imidazolium iodide 4. Depending on the reaction conditions, treatment of the 6-chlorouracil 5 with DMAP resulted in the formation of the pyridinium uracilate 6, the uracilyl pyridinium chloride 7a, and the novel pyridinium-uracilate 8 which is a cross-conjugated mesomeric betaine (CCMB). Alkylation of the mesomeric betaine 8 with 1,2-dichloroethane/SbCl 5 gave the biscation 9. Analogously, 1-methylimidazole or 2,4,6trimethylpyridine as nucleophiles formed the salts 10a and 12, respectively, and the imidazoliumuracilate 11. This is the first representative of a cross-conjugated heterocyclic mesomeric betaine isoconjugate with odd nonalternant hydrocarbon anions. PM3 calculations were performed on the cation 2 and on the mesomeric betaine 8. Whereas the cation 2 was found to have an essentially perpendicular torsional angle Φ around the CN + bond linking the uracil and the pyridinium units, the mesomeric betaine 8 adopts a nearly planar conformation, thus allowing stabilizing π interactions. Accordingly, upon rotation about the CN + bond, the expected maxima were found at essentially perpendicular conformations. Due to the balance between three effects which act in opposite directions, (i) stabilizing p overlap, (ii) N(8)/2-H attractive interaction, and (iii) steric repulsion between 6-H and 12-H, two additional small minima were surprisingly found at Φ ) 36.6°and 219.3°. The charge separation in the ground state of the mesomeric betaine 11, and the ground-state ion-pair complexes of the hetarenium iodides 2d, 4, 7c, and 10b were confirmed by the effect of negative solvatochromism. X

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¹H,¹³C and¹⁹F NMR spectroscopy of polyfluorinated ureas. Correlations involving NMR chemical shifts and electronic substituent effects

et al. 2005

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Seventeen N-(mono-, di-, tri-, tetra- and penta-fluorophenyl)-N'-(3-nitrophenyl)ureas were prepared and characterized. Complete assignment of their (1)H, (13)C and (19)F NMR data was undertaken and the correlation of the chemical shifts of the ureido protons with field-inductive and mesomeric electronic substituent parameters was studied using the Swain-Lupton model. The best correlations were obtained when the study was limited to certain substitution patterns, e.g. non-ortho, mono-ortho- and di-ortho-fluorinated ureas, which reveal probable changes in conformations caused by the degree of ortho fluorination at the phenyl ring. Additionally, there is an excellent linear cross-correlation between the chemical shifts of the fluorine atoms and the ipso carbon atoms for the whole group of fluorinated ureas.

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NMR studies of N-(benzimidazol-2-yl)pyridinium derivatives: QSAR with the anti-leishmanial activity and their carbon-13 NMR chemical shifts

Cited by 8 publications

References 11 publications

Heteroaromatic Tripoles. 2,6-Bis(hetarenio)pyrimidin-4-olates: Hybrids between Hetarenium Salts and Cross-Conjugated Mesomeric Betaines

Heteroaromatic Tripoles. 2,6-Bis(hetarenio)pyrimidin-4-olates: Hybrids between Hetarenium Salts and Cross-Conjugated Mesomeric Betaines

Charged and Betainic Nucleobases. On Syntheses and Properties of First Mesomeric Uracilylbetaines, Uracilates, and Novel Uracilium Salts

¹H,¹³C and¹⁹F NMR spectroscopy of polyfluorinated ureas. Correlations involving NMR chemical shifts and electronic substituent effects

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NMR studies of N-(benzimidazol-2-yl)pyridinium derivatives: QSAR with the anti-leishmanial activity and their carbon-13 NMR chemical shifts

Cited by 8 publications

References 11 publications

Heteroaromatic Tripoles. 2,6-Bis(hetarenio)pyrimidin-4-olates: Hybrids between Hetarenium Salts and Cross-Conjugated Mesomeric Betaines

Heteroaromatic Tripoles. 2,6-Bis(hetarenio)pyrimidin-4-olates: Hybrids between Hetarenium Salts and Cross-Conjugated Mesomeric Betaines

Charged and Betainic Nucleobases. On Syntheses and Properties of First Mesomeric Uracilylbetaines, Uracilates, and Novel Uracilium Salts

1H,13C and19F NMR spectroscopy of polyfluorinated ureas. Correlations involving NMR chemical shifts and electronic substituent effects

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¹H,¹³C and¹⁹F NMR spectroscopy of polyfluorinated ureas. Correlations involving NMR chemical shifts and electronic substituent effects