Heteromerous Bistricyclic Aromatic Enes: Dynamic Stereochemistry of Xanthylidene-Anthrones

M. Rachel Suissa; Shmuel Cohen; Sergey Pogodin; Israel Agranat

doi:10.1002/chir.22500

Heteromerous Bistricyclic Aromatic Enes: Dynamic Stereochemistry of Xanthylidene-Anthrones

M. Rachel Suissa
, Shmuel Cohen
, Sergey Pogodin
, Israel Agranat^*

^*Corresponding author for this work

Institute of Chemistry

Research output: Contribution to journal › Article › peer-review

2 Scopus citations

Abstract

The heteromerous bistricyclic aromatic ene (BAE) 2,2'-dimethyl-10-(9H-xanthylidene)-9(10H)-anthrone (DMXA) was synthesized by a condensation of 10,10-dichloro-2-methylxanthene with 2-methylanthrone. X-ray crystallography of (E)-DMXA and xanthylidene-anthrone (XA) indicated that the molecules adopt anti-folded conformations with folding dihedral angles of 44°/44° and 39°/41°, respectively. The crystal structure of anti-folded (E)-DMXA does not indicate any xanthenylium-anthracenolate push-pull effect. E,Z-diastereomerization of DMXA was studied by ¹H-NMR coalescence-temperature measurements at different magnetic field strengths and by kinetic equilibration experiments. Free energy of activation for this process was 81.5 (±1.3) kJ/mol. B3LYP/6-311+G(d,p) calculations showed that anti-folded conformers of XA, (E)-DMXA, bianthrone (AA), and dixanthylene (XX) were global minima. The twisted conformers of XA, AA, and XX were local minima (ΔG₂₉₈ = 16, 18, and 24 kJ/mol) with a substantial dipolar xanthenylium-anthracenolate dipolar contribution for XA. Chirality 27:919-928, 2015.

Original language	English
Pages (from-to)	919-928
Number of pages	10
Journal	Chirality
Volume	27
Issue number	12
DOIs	https://doi.org/10.1002/chir.22500
State	Published - 1 Dec 2015

Bibliographical note

Publisher Copyright:
© 2015 Wiley Periodicals, Inc.

Keywords

DFT calculations
DNMR
E,Z-diastereomerization
X-ray crystallography

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10.1002/chir.22500

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title = "Heteromerous Bistricyclic Aromatic Enes: Dynamic Stereochemistry of Xanthylidene-Anthrones",

abstract = "The heteromerous bistricyclic aromatic ene (BAE) 2,2'-dimethyl-10-(9H-xanthylidene)-9(10H)-anthrone (DMXA) was synthesized by a condensation of 10,10-dichloro-2-methylxanthene with 2-methylanthrone. X-ray crystallography of (E)-DMXA and xanthylidene-anthrone (XA) indicated that the molecules adopt anti-folded conformations with folding dihedral angles of 44°/44° and 39°/41°, respectively. The crystal structure of anti-folded (E)-DMXA does not indicate any xanthenylium-anthracenolate push-pull effect. E,Z-diastereomerization of DMXA was studied by 1H-NMR coalescence-temperature measurements at different magnetic field strengths and by kinetic equilibration experiments. Free energy of activation for this process was 81.5 (±1.3) kJ/mol. B3LYP/6-311+G(d,p) calculations showed that anti-folded conformers of XA, (E)-DMXA, bianthrone (AA), and dixanthylene (XX) were global minima. The twisted conformers of XA, AA, and XX were local minima (ΔG298 = 16, 18, and 24 kJ/mol) with a substantial dipolar xanthenylium-anthracenolate dipolar contribution for XA. Chirality 27:919-928, 2015.",

keywords = "DFT calculations, DNMR, E,Z-diastereomerization, X-ray crystallography",

author = "Suissa, \{M. Rachel\} and Shmuel Cohen and Sergey Pogodin and Israel Agranat",

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AU - Suissa, M. Rachel

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AU - Pogodin, Sergey

AU - Agranat, Israel

PY - 2015/12/1

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N2 - The heteromerous bistricyclic aromatic ene (BAE) 2,2'-dimethyl-10-(9H-xanthylidene)-9(10H)-anthrone (DMXA) was synthesized by a condensation of 10,10-dichloro-2-methylxanthene with 2-methylanthrone. X-ray crystallography of (E)-DMXA and xanthylidene-anthrone (XA) indicated that the molecules adopt anti-folded conformations with folding dihedral angles of 44°/44° and 39°/41°, respectively. The crystal structure of anti-folded (E)-DMXA does not indicate any xanthenylium-anthracenolate push-pull effect. E,Z-diastereomerization of DMXA was studied by 1H-NMR coalescence-temperature measurements at different magnetic field strengths and by kinetic equilibration experiments. Free energy of activation for this process was 81.5 (±1.3) kJ/mol. B3LYP/6-311+G(d,p) calculations showed that anti-folded conformers of XA, (E)-DMXA, bianthrone (AA), and dixanthylene (XX) were global minima. The twisted conformers of XA, AA, and XX were local minima (ΔG298 = 16, 18, and 24 kJ/mol) with a substantial dipolar xanthenylium-anthracenolate dipolar contribution for XA. Chirality 27:919-928, 2015.

AB - The heteromerous bistricyclic aromatic ene (BAE) 2,2'-dimethyl-10-(9H-xanthylidene)-9(10H)-anthrone (DMXA) was synthesized by a condensation of 10,10-dichloro-2-methylxanthene with 2-methylanthrone. X-ray crystallography of (E)-DMXA and xanthylidene-anthrone (XA) indicated that the molecules adopt anti-folded conformations with folding dihedral angles of 44°/44° and 39°/41°, respectively. The crystal structure of anti-folded (E)-DMXA does not indicate any xanthenylium-anthracenolate push-pull effect. E,Z-diastereomerization of DMXA was studied by 1H-NMR coalescence-temperature measurements at different magnetic field strengths and by kinetic equilibration experiments. Free energy of activation for this process was 81.5 (±1.3) kJ/mol. B3LYP/6-311+G(d,p) calculations showed that anti-folded conformers of XA, (E)-DMXA, bianthrone (AA), and dixanthylene (XX) were global minima. The twisted conformers of XA, AA, and XX were local minima (ΔG298 = 16, 18, and 24 kJ/mol) with a substantial dipolar xanthenylium-anthracenolate dipolar contribution for XA. Chirality 27:919-928, 2015.

KW - DFT calculations

KW - DNMR

KW - E,Z-diastereomerization

KW - X-ray crystallography

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ER -

Heteromerous Bistricyclic Aromatic Enes: Dynamic Stereochemistry of Xanthylidene-Anthrones

Abstract

Bibliographical note

Keywords

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