D2-Symmetric dimer of 1,1'-binaphthyl and its chiral π-conjugated carbodianion

Andrzej Rajca, Andrej Safronov, Suchada Rajca, Jirawat Wongsriratanakul

Research output: Contribution to journalArticle

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Abstract

The synthesis of a chiral, nonracemic π-conjugated system with D2 point group of symmetry and the corresponding chiral carbodianion is described. Cu(II)-mediated oxidation of (R)-2,2'-dilithio-1,1'-binaphthyl (prepared from (R)(+)- 2,2'-dibromo-1,1'-binaphthyl) gives the corresponding dimer, (R)(+)-3, which is a chiral π-conjugated derivative of o- tetraphenylene, a saddle shaped molecule. When partially resolved 2,2'- dibromo-1,1',-binaphthyl is used, amplification of the enantiomeric excess (ee) is observed in the coupling product (3). The dihedral angles between the naphthalene moieties in (R)(+)-3 are about 70 °, as determined by the X-ray crystallography. However, CD and UV spectra, and cyclic voltammetric data of (R)(+)-3 are consistent with small, but far from negligible, conjugation (or homoconjugation) between the naphthalene moieties. The melting points of (R)(+)-3 and its racemate differ by more than 200 °C. Reaction of (R)(+)-3 with Li or Na in tetrahydrofuran (THF) gives the corresponding chiral carbodianions 32-,2M+ (M = Li and Na). NMR spectroscopy indicates two non- equivalent naphthalene moieties. UV-vis, ESR, NMR, and electrochemical studies show almost complete disproportionation of the radical anion to the carbodianion in THF with Na+ as counterions. The free energy bather for racemization in carbodianion 32-,2Na+ is lowered by at least 25 kcal/mol compared to that in (R)(+)-3. However, carbodianions 32-,2M+ (M = Li and Na) remain configurationally stable at room temperature. Solid 32-,2Na+ is a diamagnetic insulator.

Original languageEnglish (US)
Pages (from-to)3351-3357
Number of pages7
JournalJournal of the American Chemical Society
Volume122
Issue number14
DOIs
StatePublished - Apr 12 2000

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Naphthalene
Dimers
Point groups
X ray crystallography
X Ray Crystallography
Crystal symmetry
Dihedral angle
Freezing
Nuclear magnetic resonance spectroscopy
Free energy
Anions
Amplification
Paramagnetic resonance
Melting point
Magnetic Resonance Spectroscopy
Negative ions
Nuclear magnetic resonance
Derivatives
Oxidation
Molecules

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

D2-Symmetric dimer of 1,1'-binaphthyl and its chiral π-conjugated carbodianion. / Rajca, Andrzej; Safronov, Andrej; Rajca, Suchada; Wongsriratanakul, Jirawat.

In: Journal of the American Chemical Society, Vol. 122, No. 14, 12.04.2000, p. 3351-3357.

Research output: Contribution to journalArticle

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abstract = "The synthesis of a chiral, nonracemic π-conjugated system with D2 point group of symmetry and the corresponding chiral carbodianion is described. Cu(II)-mediated oxidation of (R)-2,2'-dilithio-1,1'-binaphthyl (prepared from (R)(+)- 2,2'-dibromo-1,1'-binaphthyl) gives the corresponding dimer, (R)(+)-3, which is a chiral π-conjugated derivative of o- tetraphenylene, a saddle shaped molecule. When partially resolved 2,2'- dibromo-1,1',-binaphthyl is used, amplification of the enantiomeric excess (ee) is observed in the coupling product (3). The dihedral angles between the naphthalene moieties in (R)(+)-3 are about 70 °, as determined by the X-ray crystallography. However, CD and UV spectra, and cyclic voltammetric data of (R)(+)-3 are consistent with small, but far from negligible, conjugation (or homoconjugation) between the naphthalene moieties. The melting points of (R)(+)-3 and its racemate differ by more than 200 °C. Reaction of (R)(+)-3 with Li or Na in tetrahydrofuran (THF) gives the corresponding chiral carbodianions 32-,2M+ (M = Li and Na). NMR spectroscopy indicates two non- equivalent naphthalene moieties. UV-vis, ESR, NMR, and electrochemical studies show almost complete disproportionation of the radical anion to the carbodianion in THF with Na+ as counterions. The free energy bather for racemization in carbodianion 32-,2Na+ is lowered by at least 25 kcal/mol compared to that in (R)(+)-3. However, carbodianions 32-,2M+ (M = Li and Na) remain configurationally stable at room temperature. Solid 32-,2Na+ is a diamagnetic insulator.",
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N2 - The synthesis of a chiral, nonracemic π-conjugated system with D2 point group of symmetry and the corresponding chiral carbodianion is described. Cu(II)-mediated oxidation of (R)-2,2'-dilithio-1,1'-binaphthyl (prepared from (R)(+)- 2,2'-dibromo-1,1'-binaphthyl) gives the corresponding dimer, (R)(+)-3, which is a chiral π-conjugated derivative of o- tetraphenylene, a saddle shaped molecule. When partially resolved 2,2'- dibromo-1,1',-binaphthyl is used, amplification of the enantiomeric excess (ee) is observed in the coupling product (3). The dihedral angles between the naphthalene moieties in (R)(+)-3 are about 70 °, as determined by the X-ray crystallography. However, CD and UV spectra, and cyclic voltammetric data of (R)(+)-3 are consistent with small, but far from negligible, conjugation (or homoconjugation) between the naphthalene moieties. The melting points of (R)(+)-3 and its racemate differ by more than 200 °C. Reaction of (R)(+)-3 with Li or Na in tetrahydrofuran (THF) gives the corresponding chiral carbodianions 32-,2M+ (M = Li and Na). NMR spectroscopy indicates two non- equivalent naphthalene moieties. UV-vis, ESR, NMR, and electrochemical studies show almost complete disproportionation of the radical anion to the carbodianion in THF with Na+ as counterions. The free energy bather for racemization in carbodianion 32-,2Na+ is lowered by at least 25 kcal/mol compared to that in (R)(+)-3. However, carbodianions 32-,2M+ (M = Li and Na) remain configurationally stable at room temperature. Solid 32-,2Na+ is a diamagnetic insulator.

AB - The synthesis of a chiral, nonracemic π-conjugated system with D2 point group of symmetry and the corresponding chiral carbodianion is described. Cu(II)-mediated oxidation of (R)-2,2'-dilithio-1,1'-binaphthyl (prepared from (R)(+)- 2,2'-dibromo-1,1'-binaphthyl) gives the corresponding dimer, (R)(+)-3, which is a chiral π-conjugated derivative of o- tetraphenylene, a saddle shaped molecule. When partially resolved 2,2'- dibromo-1,1',-binaphthyl is used, amplification of the enantiomeric excess (ee) is observed in the coupling product (3). The dihedral angles between the naphthalene moieties in (R)(+)-3 are about 70 °, as determined by the X-ray crystallography. However, CD and UV spectra, and cyclic voltammetric data of (R)(+)-3 are consistent with small, but far from negligible, conjugation (or homoconjugation) between the naphthalene moieties. The melting points of (R)(+)-3 and its racemate differ by more than 200 °C. Reaction of (R)(+)-3 with Li or Na in tetrahydrofuran (THF) gives the corresponding chiral carbodianions 32-,2M+ (M = Li and Na). NMR spectroscopy indicates two non- equivalent naphthalene moieties. UV-vis, ESR, NMR, and electrochemical studies show almost complete disproportionation of the radical anion to the carbodianion in THF with Na+ as counterions. The free energy bather for racemization in carbodianion 32-,2Na+ is lowered by at least 25 kcal/mol compared to that in (R)(+)-3. However, carbodianions 32-,2M+ (M = Li and Na) remain configurationally stable at room temperature. Solid 32-,2Na+ is a diamagnetic insulator.

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