Synthesis of 2,5-diarylthiophenes from 1,4-diaryl-1,3-diynes using the trithiocarbonate anion as a nucleophile

2,5-diarylthiophenes are of great interest in materials science, being intensively applied as organic conductor materials in polymer chemistry. Recently, this class of compounds has been employed in the construction of solar cells, with great energy conversion. By the synthetic view point, these compounds can be prepared by Paal-Knorr reaction (from 1,4- dicarbonyl compounds) or cross-coupling reactions, like Suzuki coupling. However, these methods are usually related to long reaction times or expensive reagents. A promising method to achieve these compounds involves the cyclization of 1,4-diaryl-1,3-diynes in the presence of nucleophilic sulfur sources, as Na2S.9H2O, NaHS or even elemental sulfur in superbasic conditions.
In this work, we have developed a new method for the synthesis of these heterocycles from 1,4-diaryl-1,3-diynes, applying trithiocarbonate anion (CS32-) as a sulfur source for the S2- synthon in these cyclizations, being a simple, inexpensive and efficient method for the synthesis of 2,5-diarylthiophenes.