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Conformational analysis of calixarene derivatives substituted at the methylene bridges
Author(s) -
Simaan Samah,
Biali Silvio E.
Publication year - 2004
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/poc.791
Subject(s) - chemistry , calixarene , substituent , conformational isomerism , methylene bridge , steric effects , methylene , alkyl , aryl , stereochemistry , group (periodic table) , crystallography , medicinal chemistry , molecule , organic chemistry
The conformation of tetrahydroxycalix[4]arene derivatives substituted at two opposite methylene bridges or at a single bridge by an alkyl or aryl group is reviewed. The cone form with an equatorial substituent is the lowest energy conformation of calixarenes possessing one bridge substituted by an alkyl group, whereas both the axial and equatorial conformers are similarly populated if the substituent is an aryl group. In the cone conformation of calixarenes possessing two opposite bridges substituted in trans fashion by a pair of groups, one group must necessarily be located in an axial position. The steric interactions ensuing from the presence of an axial group destabilize the cone conformation, rendering the 1,2‐alternate form the lowest energy conformation in some derivatives. Copyright © 2004 John Wiley & Sons, Ltd.