Thienothiophene usually refers to any of three structurally related derivatives of

thiophene Thiophene is a heterocyclic compound with the formula C4H4S. Consisting of a planar five-membered ring, it is aromatic as indicated by its extensive substitution reactions. It is a colorless liquid with a benzene-like odor. In most of its react ...

with the formula C₆H₄S₂. In order of importance, they are: 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. Thieno ,3-bhiophene was the first member of the series to be isolated. It was obtained in very low yield upon heating

citric acid Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in ...

, a source of a six-carbon linear chain, with P₄S₁₀. More efficient syntheses of this and the other two stable thienothiophenes involve cyclization reactions of substituted thiophenes. Three thienothiophenes, being aromatic and bicyclic, are often compared with naphthalene. They are the topic of academic research. They have no commercial applications nor are they or their derivatives found naturally. File:Thienothiophene251-41-2.png, Thieno

,2-b The comma is a punctuation mark that appears in several variants in different languages. It has the same shape as an apostrophe or single closing quotation mark () in many typefaces, but it differs from them in being placed on the baseline ...

hiophene
CAS RN 251-41-2
m.p. 56.0-56.5 °C
white solid. File:Thienothiophene250-84-0.png, Thieno ,3-bhiophene
CAS RN 250-84-0
b.p. 102 °C at 16 mmHg
colorless oil. File:Thienothiophene250-65-7.png, Thieno ,4-bhiophene
CAS RN 250-65-7
m.p. 7.0-7.5 °C
colorless oil. File:24976-21-4S(IV).png, 2λ4δ2-Thieno ,4-chiophene
CAS RN 24976-21-4
not isolated.

References

{{Reflist Sulfur heterocycles Heterocyclic compounds with 2 rings