Synthesis of 2-(hetero) arylthieno [2, 3-b] or [3, 2-b] pyridines from 2, 3-dihalopyridines,(hetero) arylalkynes, and Na 2 S. Further functionalizations
A simple and efficient three-step methodology is described for the first time for the synthesis of 2-(hetero) arylthieno [2, 3-b] or [3, 2-b] pyridines. The first step is a Sonogashira coupling from 3-bromo-2-chloropyridine or 2-bromo-3-chloropyridine with several (hetero) arylalkynes to obtain the corresponding 2-or 3-chloro (hetero) arylethynylpyridines. These were cyclized by treatment with Na2S affording the expected 2-(hetero) ...