Thienothiophene

In organic chemistry, thienothiophene is any of several compounds consisting of two fused thiophene rings.

[1][2] 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.

[3] More efficient syntheses of this and the other two stable thienothiophenes involve cyclization reactions of substituted thiophenes.

[1] Three thienothiophenes, being aromatic and bicyclic, are often compared to naphthalene.