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NMR spectroscopic and ab initio MO study of sterically hindered 2,3‐disubstituted quinoxalines
Author(s) -
Kleinpeter E.,
Hilfert L.,
Koch A.
Publication year - 1999
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(199909)12:9<725::aid-poc186>3.0.co;2-i
Subject(s) - chemistry , steric effects , substituent , ab initio , conformational isomerism , computational chemistry , ab initio quantum chemistry methods , carbon 13 nmr , stereochemistry , molecule , organic chemistry
A number of quinoxalines substituted in position 2 with the π‐electron excess 2′‐benzo[ b ]furanyl substituent were studied with respect to the sterically/electronically restricted rotation about the C(2)—C(2′) bond by 13 C and 15 N chemical shifts (both experimental and calculated by the GIAO method) and ab initio MO calculations. Both the barriers to rotation and the preferred ground‐state conformers were obtained, which proved strongly dependent on steric hindrance and the balance of π‐electron deficiency π‐electron excess of the heterocyclic systems involved. Copyright © 1999 John Wiley & Sons, Ltd.