Informational rigidity in mesitylene-based calix[4]arenes adopting a 1,3-alternate conformation

Paweł Parzuchowski , Volker Böhmer , Silvio E Biali , Iris Thondorf

Abstract

Two chiral derivatives of a mesitylene-based calix[4]arene known to exist in the 1,3-alternate conformation were prepared by the attachment of homochiral residues to the four exo-hydroxy groups. Thus, the enantiotopic protons of the central scaffold became diastereotopic, leading to a doubling of their 1H NMR signals in one example. From the temperature independence of the NMR spectrum, a lower limit of 24.2 kcal/mol could be estimated for the barrier of ring inversion. MM3 calculations confirm the 1,3-alternate conformation as the energy minimum, and estimate a barrier of 25.7 kcal/mol for the 1,3-alternate-to-1,3-alternate* interconversion process. This high barrier is due to the repulsive steric interactions between exo-methyl groups at vicinal rings when these groups pass each other.
Author Paweł Parzuchowski (FC / CPCT)
Paweł Parzuchowski,,
- Chair Of Polymer Chemistry And Technology
, Volker Böhmer - [Abteilung Lehramt Chemie]
Volker Böhmer,,
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, Silvio E Biali - [Hebrew University of Jerusalem]
Silvio E Biali,,
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, Iris Thondorf - [Martin-Universitat Halle-Wittenberg]
Iris Thondorf,,
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Journal seriesTetrahedron-Asymmetry, ISSN 0957-4166
Issue year2000
Vol11
No11
Pages2393-2402
ASJC Classification1604 Inorganic Chemistry; 1605 Organic Chemistry; 1606 Physical and Theoretical Chemistry; 1503 Catalysis
DOIDOI:10.1016/S0957-4166(00)00177-4
URL http://www.sciencedirect.com/science/article/pii/S0957416600001774
Score (nominal)30
Score sourcejournalList
Publication indicators Scopus Citations = 14; WoS Citations = 14; Scopus SNIP (Source Normalised Impact per Paper): 2000 = 1.048; WoS Impact Factor: 2006 = 2.468 (2) - 2007=2.46 (5)
Citation count*13 (2015-10-25)
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* presented citation count is obtained through Internet information analysis and it is close to the number calculated by the Publish or Perish system.
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