Acid-induced conformational switching of aromatic N-methyl-N-(2-pyridyl)amides

Tetrahedron Letters

Volumn 48, Issue 4, 2007, Pages 573-577

  Okamoto, Iwao ^a   Nabeta, Mayumi ^a   Minami, Toshikatsu ^a   Nakashima, Akio ^a   Morita, Nobuyoshi ^a   Takeya, Tetsuya ^a   Masu, Hyuma ^b   Azumaya, Isao ^b   Tamura, Osamu ^a  

^a SHOWA PHARMACEUTICAL UNIVERSITY   (Japan)

^b TOKUSHIMA BUNRI UNIVERSITY   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

ACID; AMIDE; AROMATIC COMPOUND; N METHYL N (2 PYRIDYL)AMIDE; PYRIDINE DERIVATIVE; TRIFLUOROACETIC ACID; UNCLASSIFIED DRUG;

ARTICLE; CHEMICAL STRUCTURE; CONFORMATIONAL TRANSITION; CRYSTAL STRUCTURE; CRYSTALLIZATION; METHYLATION; NUCLEAR OVERHAUSER EFFECT; PROTON NUCLEAR MAGNETIC RESONANCE; PROTON TRANSPORT; STEREOCHEMISTRY; STRUCTURE ANALYSIS; X RAY CRYSTALLOGRAPHY;

EID: 33845748565     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.tetlet.2006.11.113     Document Type: Article

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13. 2) were 0.0444 and 0.1111 (all data). CCDC-625148.
14. The dihedral angle of the amide plane and C-pyridine was defined as that of N2-C7-C8-N3 (37.0°). Similarly, the dihedral angle of the amide plane and N-pyridine was defined as that of C7-N2-C1-C2 (45.5°).
15. 2) were 0.0687 and 0.1367 (all data). CCDC-625151.
16. 10: C, 41.62; H, 3.49; N, 12.77. Found: C, 41.87; H, 3.31; N, 12.77.
17. 1H NMR spectra of 1, 1H, 2, and 2H revealed similar tendency of lower field shifts as that of 3 in Figure 3. The slight differences are as follows: 1 was less protonated by TFA in comparison to 1H, and 2 was more protonated by TFA in comparison to 2H. These are reasonable because one carbonyl oxygen should form two intramolecular hydrogen bonds in diprotonated 1, and the central pyridine ring of 2 can be considered as more basic than that of 3. In this point of view, it is also clear that the absence of lower field shift of H-3 (Table 1, entry 2) indicates the difference of conformational change of 1 and 2.
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21. 2) were 0.0973 and 0.1890, respectively (all data). CCDC-625152.