| 摘要 |
<p>In accordance with a novel process, 2,3-difluoropyridines of formula I <IMAGE> (I) wherein X is halogen or trifluoromethyl, are prepared by diazotising a 3-amino-2-halopyridine of formula II <IMAGE> (II) wherein X is as defined for formula I and Y is bromine, chlorine or fluorine, in the presence of hydrogen fluroide, to give a 3-fluoro-2-halopyridine of formula III <IMAGE> (III) wherein X and Y are as defined for formula II, and treating resultant 3-fluoro-2-halopyridines of formula III, wherein Y is bromine or chlorine, with a fluorinating agent. The 2,3-difluoropyridines prepared by the novel process are valuable intermediates for the preparation of 2-[4-(3-fluoropyridin-2-yloxy)-phenoxy]propionic acid derivatives which are known as herbicides.</p> |
