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Conformational Analysis of Benzoannulated Nine‐Membered Rings, 5. 1,2,6,7‐Tetrahydro‐4 H ‐3,5‐benzodioxonin
Author(s) -
Rys Barbara,
Szneler Edward,
Duddeck Helmut
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619960510
Subject(s) - chemistry , ring flip , racemization , ring (chemistry) , anomer , enantiomer , ground state , coalescence (physics) , stereochemistry , hydrogen bond , crystallography , anomeric effect , computational chemistry , molecule , organic chemistry , physics , astrobiology , quantum mechanics
Temperature‐dependent 1 H‐ and 13 C‐NMR spectra of the title compound are presented. Coalescence effects are discussed and assigned to two dynamic processes: (a) ring inversion of the nine‐membered ring, (b) racemization of the enantiomeric ground‐state conformations of the nine‐membered ring. The barriers are 52 and 35 kJ mol −1 , respectively. The stability of the ground state conformation is discussed in terms of transannular hydrogen interactions and anomeric effects. An assignment of the proton signals in the groundstate conformation is proposed.