Thienothiophene

In organic chemistry, thienothiophene is any of several compounds consisting of two fused thiophene rings. They have the molecular formula C6H4S2. Three constitutional isomers have been synthesized: thieno[3,2-b]thiophene, thieno[2,3-b]thiophene, and thieno[3,4-b]thiophene. Other isomers feature S(IV) and are less stable.[1] Thieno[2,3-b]thiophene was the first member of the series to be isolated. It was obtained in very low yield upon heating citric acid, a source of a six-carbon linear chain, with P4S10.[2] More efficient syntheses of this and the other two stable thienothiophenes involve cyclization reactions of substituted thiophenes.[3]

Thieno[3,2-b]thiophene

Three thienothiophenes, being aromatic and bicyclic, are often compared to naphthalene. They are the topic of academic research. They have no commercial applications nor are they or their derivatives found naturally.

  • Isomers of thienothiophene
  • Thieno[3,2-b]thiopheneCAS RN 251-41-2m.p. 56.0-56.5 °Cwhite solid.
    Thieno[3,2-b]thiophene
    CAS RN 251-41-2
    m.p. 56.0-56.5 °C
    white solid.
  • Thieno[2,3-b]thiopheneCAS RN 250-84-0b.p. 102 °C at 16 mmHgcolorless oil.
    Thieno[2,3-b]thiophene
    CAS RN 250-84-0
    b.p. 102 °C at 16 mmHg
    colorless oil.
  • Thieno[3,4-b]thiopheneCAS RN 250-65-7m.p. 7.0-7.5 °Ccolorless oil.
    Thieno[3,4-b]thiophene
    CAS RN 250-65-7
    m.p. 7.0-7.5 °C
    colorless oil.
  • 2λ4δ2-Thieno[3,4-c]thiopheneCAS RN 24976-21-4not isolated.
    2λ4δ2-Thieno[3,4-c]thiophene
    CAS RN 24976-21-4
    not isolated.[4]

References
  1. Cava, Michael P.; Lakshmikantham, M. V. (1975). "Nonclassical Condensed Thiophenes". Accounts of Chemical Research. 8 (4): 139–44. doi:10.1021/ar50088a005.
  2. Litvinov, V. P.; Gol'dfarb, Y. A. L. (1976). "The Chemistry of Thienothiophenes and Related Systems". Advances in Heterocyclic Chemistry. Advances in Heterocyclic Chemistry. Vol. 19. pp. 123–214. doi:10.1016/S0065-2725(08)60231-7. ISBN 9780120206193.
  3. Cinar, M. E.; Ozturk, T. (2015). "Thienothiophenes, Dithienothiophenes, and Thienoacenes: Syntheses, Oligomers, Polymers, and Properties". Chemical Reviews. 115 (9): 3036–3140. doi:10.1021/cr500271a. PMID 25831021.
  4. Nakayama, Juzo; Ishii, Akihiko; Kobayashi, Yasunobu; Hoshino, Masamatsu (1988). "Generation and Characterization of the Parent 2λ4δ2-Thieno[3,4-c]thiophene". Journal of the Chemical Society, Chemical Communications. 14 (14): 959–60. doi:10.1039/C39880000959.
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