Axially chiral pyridine compounds: synthesis, chiral separations and determination of protonation dependent barriers to hindered rotation
TETRAHEDRON-ASYMMETRY, cilt.25, sa.5, ss.449-456, 2014 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 25 Sayı: 5
- Basım Tarihi: 2014
- Doi Numarası: 10.1016/j.tetasy.2014.01.012
- Dergi Adı: TETRAHEDRON-ASYMMETRY
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Index Chemicus (IC)
- Sayfa Sayıları: ss.449-456
- İstanbul Üniversitesi-Cerrahpaşa Adresli: Hayır
Özet
Axially chiral enantiomeric 2-pyridylimino-3-pyridyl-thiazolidine-4-ones and -thiones have been synthesized and their rotational barriers around the N-3((pyridyl)) bond have been determined by variable temperature NMR or by thermal racemization of the micropreparatively resolved enantiomers. Rotational barriers of the unprotonated compounds ranged from 46 to 116 kJ/mol depending on the substituent on the N-3-pyridyl ring and on the exocyclic oxygen or sulfur atoms of the thiazolidine ring. Protonation of the pyridine nitrogens by TFA caused a decrease in the barrier to the rotation by stabilizing the transition state of the rotations via hydrogen bonding interactions. (C) 2014 Elsevier Ltd. All rights reserved.