Synthesis of Trisubstituted Pyridines via Chemoselective Suzuki–Miyaura Coupling of 3,5- and 4,6-Dibromo-2-tosyloxypyridines

Chemoselective Suzuki–Miyaura reactions on 3,5- and 4,6-dibromo-2-tosyloxypyridines have been studied for the preparation of trisubstituted pyridines. The optimized conditions allow for a facile access to 3,5- and 4,6-diaryl-2-tosyloxypyridines in yields of 8 to 99%. Further functionalization such as palladium-catalyzed amination and copper-free Sonogashira reaction of the tosylate group in the diarylpyridine derivatives obtained was accomplished for the synthesis of novel and biologically relevant trisubstituted pyridines. The formal synthesis of ficuseptine, a bioactive alkaloid, has also been achieved via the palladium-catalyzed cross-coupling reaction of 3,5-dibromo-2-tosyloxypyridine in 5 steps from 3,5-dibromo-2-hydroxypyridine with 50% overall yield. (Figure presented.).