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Carbon‐13 NMR spectra of 1,4‐benzodiazepines—influence of the 7‐substituent
Author(s) -
Paul H.H.,
Sapper H.,
Lohmann W.,
Kalinowski H. O.
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.1270210507
Subject(s) - substituent , chemistry , amide , spectral line , electron , polarization (electrochemistry) , hydrogen bond , hydrogen , carbon 13 nmr , nmr spectra database , proton , crystallography , medicinal chemistry , stereochemistry , photochemistry , molecule , organic chemistry , physics , quantum mechanics , astronomy
Carbon‐13 NMR spectra of 1,4‐benzodiazepines, substituted differently at C‐7, are reported. With increasing electron demand of the substituent the signal of C‐2 is shifted upfield, an effect which is interpreted in terms of a π‐polarization of the carbonyl π‐electrons. This mechanism also seems to be of importance for the π‐electrons of the 5‐phenyl substituent and of the (N‐4)(C‐5) bond. Owing to the formation of hydrogen‐bonded self‐associates, compounds with a free amide group show concentration‐dependent shifts of some resonances. This is most obvious for C‐2, the proposed proton accepting site for hydrogen‐bonded cyclic dimers.