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Carbon‐13 delta shifts and steric interactions in N ‐aryl‐1‐isoindolinones and Isoindoline‐1,3‐diones
Author(s) -
Khadim Mohammad A.,
Colebrook L. D.
Publication year - 1985
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260230410
Subject(s) - chemistry , steric effects , aryl , isoindoline , methylene , medicinal chemistry , stereochemistry , organic chemistry , alkyl
Consistently deshielding 13 C δ shifts resulting from the presence of aryl ortho substituents have been measured for the 3‐methylene carbon atoms of some N ‐aryl‐1‐isoindolinones (0.12‐3.25 ppm) and for the carbonyl carbon atoms of these compounds and corresponding N ‐arylisoindoline‐1,3‐diones (0.04‐1.47 ppm). Low‐temperature (−75 and −150 °C) 1 H NMR studies indicate that steric barriers to internal rotation about the aryl CN bonds in the N ‐aryl‐1‐isoindolinones are low. The compounds with the bulkiest aryl ortho substituents tend to show the largest δ shifts (particularly for the 3‐methylene carbons). No consistent correlation with the size of aryl ortho ‐substituents or their expected electronic properties is evident.