Aromatic Fluorine Compounds. IX. 2-Fluoropyridines

Abstract

The synthesis of 2-fluoro-3-nitropyridine, 2-fluoro-5-nitropyridine and 3-bromo-2-fluoro-5-nitropyridine from the corresponding chloropyridines in yields exceeding 50% has been accomplished in dimethylformamide by replacement of -Cl by-F using potassium fluoride. The 3-bromine as well as the 5-nitro group activates the 2-position as shown by the increased reaction velocity of the 2-chlorine in 3-bromo-2-chloro-5-nitropyridine as compared with 2-chloro-5-nitropyridine. With 2-chloro-4-nitropyridine both groups appear to be replaced, but no 2, 4-difluoropyridine could be isolated. A fluoropyridine was not isolated by reaction of potassium fluoride with 2-bromopyridine, 2-bromopyridine-N-oxide, 2-chloropyridine or 2-chloropyridine hydrochloride. © 1959, American Chemical Society. All rights reserved.