Syntheses of 2-Chloro- and 2-Amino-5-fluoropyridines and Isolation of a Novel Difluoroboryl Imidate

The highly volatile, weakly basic 2-chloro-5-fluoropyridine (3), prepared by diazotization of 5-amino-2-chloropyridinc (1) with isoamyl nitrite/tetrafluoroboric acid followed by thermolysis (70%) has been characterized. Reaction of 3 with ammonia afforded a 3:1 mixture (40%) of 1 and 2-amino-5-fluoropyridine (4). An alternate, 5-step synthesis gave 4 in 33% overall yield from 2-amino-5-nitropyridine (5). One of the intermediates was shown to have a novel difluoroboryl imidate 10 structure.