Ring contraction during the 6π-electrocyclisation of naphthopyran valence tautomers

Christopher D. Gabbutt, B. Mark Heron, Suresh B. Kolla, Colin Kilner, Simon J. Coles, Peter N. Horton, Michael B. Hursthouse

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

The thermal and photochemical ring-opening of spiro(3H-naphtho[2,1-b]pyran- 3,9′-thioxanthene-10,10-dioxide) 3 results in the facile ring-contraction to 9-(naphtho[2,1-b]furan-2-yl)-9H-thioxanthene-10,10-dioxide 6. Similar behaviour is displayed by the isomeric spiro(2H-naphtho[1,2-b]pyran-2,9′- thioxanthene-10,10-dioxide) 9 affording 9-(naphtho[1,2-b]furan-2-yl)-9H- thioxanthene-10,10-dioxide 12, though more severe reaction conditions were required. The comparative ease of this rearrangement for the isomers 3 and 9 was rationalised on the basis of the relative isomer populations of the ring-opened naphthopyrans. The rearrangement of simple mono- and bis-methylsulfonylphenyl substituted photochromic naphthopyrans 18, 20 was examined; the former failed to rearrange whereas the latter could be induced to rearrange only under prolonged UV irradiation. The photochromism of diastereoisomerically pure sulfoxides derived from the oxidation of spiro(3H-naphtho[2,1-b]pyran-3,9′- thioxanthene) 2a and spiro(2H-naphtho[1,2-b]pyran-2,9′-thioxanthene) 2b resulted in conversion to the most thermodynamically stable trans-isomer in each case.

LanguageEnglish
Pages3096-3104
Number of pages9
JournalOrganic and Biomolecular Chemistry
Volume6
Issue number17
Early online date9 Jul 2008
DOIs
Publication statusPublished - 7 Sep 2008
Externally publishedYes

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Thioxanthenes
tautomers
dioxides
contraction
valence
isomers
rings
furans
Isomers
Sulfoxides
photochromism
Photochromism
Hot Temperature
oxidation
irradiation
Irradiation
Population
Oxidation

Cite this

Gabbutt, Christopher D. ; Heron, B. Mark ; Kolla, Suresh B. ; Kilner, Colin ; Coles, Simon J. ; Horton, Peter N. ; Hursthouse, Michael B. / Ring contraction during the 6π-electrocyclisation of naphthopyran valence tautomers. In: Organic and Biomolecular Chemistry. 2008 ; Vol. 6, No. 17. pp. 3096-3104.
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Ring contraction during the 6π-electrocyclisation of naphthopyran valence tautomers. / Gabbutt, Christopher D.; Heron, B. Mark; Kolla, Suresh B.; Kilner, Colin; Coles, Simon J.; Horton, Peter N.; Hursthouse, Michael B.

In: Organic and Biomolecular Chemistry, Vol. 6, No. 17, 07.09.2008, p. 3096-3104.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Ring contraction during the 6π-electrocyclisation of naphthopyran valence tautomers

AU - Gabbutt, Christopher D.

AU - Heron, B. Mark

AU - Kolla, Suresh B.

AU - Kilner, Colin

AU - Coles, Simon J.

AU - Horton, Peter N.

AU - Hursthouse, Michael B.

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N2 - The thermal and photochemical ring-opening of spiro(3H-naphtho[2,1-b]pyran- 3,9′-thioxanthene-10,10-dioxide) 3 results in the facile ring-contraction to 9-(naphtho[2,1-b]furan-2-yl)-9H-thioxanthene-10,10-dioxide 6. Similar behaviour is displayed by the isomeric spiro(2H-naphtho[1,2-b]pyran-2,9′- thioxanthene-10,10-dioxide) 9 affording 9-(naphtho[1,2-b]furan-2-yl)-9H- thioxanthene-10,10-dioxide 12, though more severe reaction conditions were required. The comparative ease of this rearrangement for the isomers 3 and 9 was rationalised on the basis of the relative isomer populations of the ring-opened naphthopyrans. The rearrangement of simple mono- and bis-methylsulfonylphenyl substituted photochromic naphthopyrans 18, 20 was examined; the former failed to rearrange whereas the latter could be induced to rearrange only under prolonged UV irradiation. The photochromism of diastereoisomerically pure sulfoxides derived from the oxidation of spiro(3H-naphtho[2,1-b]pyran-3,9′- thioxanthene) 2a and spiro(2H-naphtho[1,2-b]pyran-2,9′-thioxanthene) 2b resulted in conversion to the most thermodynamically stable trans-isomer in each case.

AB - The thermal and photochemical ring-opening of spiro(3H-naphtho[2,1-b]pyran- 3,9′-thioxanthene-10,10-dioxide) 3 results in the facile ring-contraction to 9-(naphtho[2,1-b]furan-2-yl)-9H-thioxanthene-10,10-dioxide 6. Similar behaviour is displayed by the isomeric spiro(2H-naphtho[1,2-b]pyran-2,9′- thioxanthene-10,10-dioxide) 9 affording 9-(naphtho[1,2-b]furan-2-yl)-9H- thioxanthene-10,10-dioxide 12, though more severe reaction conditions were required. The comparative ease of this rearrangement for the isomers 3 and 9 was rationalised on the basis of the relative isomer populations of the ring-opened naphthopyrans. The rearrangement of simple mono- and bis-methylsulfonylphenyl substituted photochromic naphthopyrans 18, 20 was examined; the former failed to rearrange whereas the latter could be induced to rearrange only under prolonged UV irradiation. The photochromism of diastereoisomerically pure sulfoxides derived from the oxidation of spiro(3H-naphtho[2,1-b]pyran-3,9′- thioxanthene) 2a and spiro(2H-naphtho[1,2-b]pyran-2,9′-thioxanthene) 2b resulted in conversion to the most thermodynamically stable trans-isomer in each case.

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U2 - 10.1039/b807744d

DO - 10.1039/b807744d

M3 - Article

VL - 6

SP - 3096

EP - 3104

JO - Organic and Biomolecular Chemistry

T2 - Organic and Biomolecular Chemistry

JF - Organic and Biomolecular Chemistry

SN - 1477-0520

IS - 17

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