Stereochemistry of a spherand-type calixarene

K. Agbaria, S. E. Biali*, V. Böhmer, J. Brenn, S. Cohen, M. Frings, F. Grynszpan, J. Mc B. Harrowfield, A. N. Sobolev, I. Thondorf

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

The stereochemistry of the spherand-type calixarene 2a is analyzed in terms of the configuration of the three 2,2′-dihydroxybiphenyl subunits (R or S) and the disposition of the methylene groups (crown or twist). X-ray crystallography indicates that the neutral 2a and its mono- or dianion (in form of the salts 2a-·C5H5NH+ and 2a2-·2Et3NH+) exist essentially in the same conformation (RRS/SSR-twist). This asymmetric RRS/SSR-twist form is the lowest energy conformer according to molecular mechanics calculations. Low-temperature 1H NMR data indicate the presence of a major conformer of C1 symmetry, in agreement with a RRS/SSR-twist form. The lowest energy topomerization pathway mutually exchanges two pairs of methylene protons and is ascribed to an enantiomerization process involving rotation around an Ar-Ar bond.

Original languageAmerican English
Pages (from-to)2900-2906
Number of pages7
JournalJournal of Organic Chemistry
Volume66
Issue number9
DOIs
StatePublished - 4 May 2001

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