Through an investigation into the behaviour of 3-acetyl-2-aminothiophene in the reaction
with Vilsmeier–Haack reagent, an efficient method for the synthesis of 4-chlorothieno[2,3-b]pyridine derivatives has been established. Gewald’s classical synthesis starting
from cyanoacetone, ketones and elemental sulphur has been applied to produce the starting
materials.
Key words
Vilsmeier–Haack - Gewald’s reaction - thieno[2,3-
b]pyridine - Buchwald–Hartwig - cross coupling