Premium
13 C NMR spectra of 2,3‐dihydro‐1 H ‐benzo[ b ]azepines: Differentiation of diastereomers
Author(s) -
Uriac Ph.,
Huet J.
Publication year - 1983
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/omr.1270210807
Subject(s) - diastereomer , chemistry , nmr spectra database , chemical shift , stereochemistry , spectral line , physics , astronomy
The 13 C NMR spectra of 23 2,3‐dihydro‐1 H ‐benzo[ b ]azepines, including nine pairs of diastereomers separated by chromatography, [(2 R *, 3 R * ) and (2 R * ), 3 S * )] are hereby assigned and discussed. The relative configurations of the diastereomers were assigned by two methods. The first, based on the chemical shifts of the asymmetric carbons C‐2 and C‐3 (with regression analysis), shows that the values for ( R * , R * ) are approximately 1 ppm lower than those for ( R * , S * ) diastereomers. The second method uses the chemical shifts, δ 3 , of the R 3 (CH 3 ) substituents. When these δ 3 values are compared by means of the δ 3 ‐δ m difference (δ m is the mean value obtained from compounds where R 2 =H), the difference is always negative for ( R * , R * ) and positive for ( R * , S * ). This is attributed to a γ‐ gauche effect between R 2 and R 3 in the case of ( R * , R * ) diastereomers (R 2 and R 3 are cis ). The results corroborate those already obtained by 1 H NMR [ J (23)( R * , R * )< J (23)( R * , S * )] and are a confirmation of the results of a radiocrystallographic examination carried out on two nitrogen acetylated diastereomers.