Symmetrical and unsymmetrical bithiophene-substituted heterocycles bearing carbonitriles including imidazo[1,2-a]pyridine, benzimidazole, and pyridine derivatives have been synthesized via different synthetic protocols. The bithiophene bis-imidazo[1,2-a]pyridine derivatives
3a,b were achieved in three steps starting from 2-acetyl-5-bromothiophene. Suzuki coupling reaction of
2a with 5-formylthiophen-2-ylboronic acid forms the formyl derivative
5, which by condensation with 3,4-diaminobenzonitrile in the presence of sodium bisulfite furnishes the unsymmetrical bithiophene derivative
6. The bis-benzimidazole derivative
8 was obtained via hexabutylditin-mediated homocoupling of 5-bromothiophene-2-carboxaldehyde, while the benzimidazole derivatives
12a,b were prepared via the formyl derivatives
11a,b, a product of Velsmier formylation reaction of
10a,b. Two synthetic protocols for the aryl/hetaryl-2,2′-bithiophene derivative
14 have also been presented. In addition, the guanyl hydrazones of bithiophenes,
16 and
17, were prepared from bis(tri-
n-butylstannyl)-2,2′-bithiophene through a Stille coupling reaction followed by a condensation step.
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