Regioselective Syntheses of 2,3,5-Trisubstituted Pyridines via 5-Chloro-3-fluoro-2-(methylsulfonyl)pyridine.

We report the high-yielding, large-scale, one-pot synthesis of two versatile building blocks (1-Cl and 1-Br) for the regioselective synthesis of a variety of 2,3,5-trisubstituted pyridines from inexpensive materials. These molecules are readily derivatized at positions 2, 3, and 5. These building blocks can also be used for the synthesis of fused pyrido-oxazines and for the synthesis of 2,3,4,5-tetrasubstituted pyridines.