Stereochemistry of a Spherand-Type Calixarene

K. Agbaria, S.E. Biali, V. Bohmer, J. Brenn, S. Cohen, M. Frings, F. Grynszpan, J.M. Harrowfield, Alexandre Sobolev, I. Thondorf

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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 as and its mono- or dianion (in form of the salts 2a(-).C5H5NH+ and 2a(2-). 2Et(3)NH(+)) 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 H-1 NMR data indicate the presence of a major conformer of C-1 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 languageEnglish
Pages (from-to)2900-2906
JournalJournal of Organic Chemistry
Volume66
DOIs
Publication statusPublished - 2001

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Agbaria, K., Biali, S. E., Bohmer, V., Brenn, J., Cohen, S., Frings, M., ... Thondorf, I. (2001). Stereochemistry of a Spherand-Type Calixarene. Journal of Organic Chemistry, 66, 2900-2906. https://doi.org/10.1021/jo0016576