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

doi:10.1021/jo0016576

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

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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 2a and its mono- or dianion (in form of the salts 2a^-·C₅H₅NH⁺ and 2a^2-·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 language	English
Pages (from-to)	2900-2906
Number of pages	7
Journal	Journal of Organic Chemistry
Volume	66
Issue number	9
DOIs	https://doi.org/10.1021/jo0016576
State	Published - 4 May 2001
Externally published	Yes

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title = "Stereochemistry of a spherand-type calixarene",

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.",

author = "K. Agbaria and Biali, {S. E.} and V. B{\"o}hmer and J. Brenn and S. Cohen and M. Frings and F. Grynszpan and Harrowfield, {J. Mc B.} and Sobolev, {A. N.} and I. Thondorf",

year = "2001",

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doi = "10.1021/jo0016576",

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T1 - Stereochemistry of a spherand-type calixarene

AU - Agbaria, K.

AU - Biali, S. E.

AU - Böhmer, V.

AU - Brenn, J.

AU - Cohen, S.

AU - Frings, M.

AU - Grynszpan, F.

AU - Harrowfield, J. Mc B.

AU - Sobolev, A. N.

AU - Thondorf, I.

PY - 2001/5/4

Y1 - 2001/5/4

N2 - 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.

AB - 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.

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JO - Journal of Organic Chemistry

JF - Journal of Organic Chemistry

IS - 9

ER -

Stereochemistry of a spherand-type calixarene

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