3,5-difluoropyridine-N-oxide is prepared by the following steps:A solution of (5) (0.37 g, 3 mmol), peracetic acid ( 1.5 cm3 of 40% solution in acetic acid) in acetic acid (5 cm3) and chloroform (10 cm3) was heated at 50 "C, with stirring, for 24 h. The mixture was neutralised by the addition of dilute sodium hydroxide to the chilled mixture, then remaining peroxides were destroyed by the addition of sodium metabisulphite (2 g). Following extraction into DCM, the DCM solution was dried (MgS04) and evaporated to dryness giving a solid which was recrystallised from DCM- petrol (1: 1) to yield 3,5-difluoropyridine-N-oxide (0.3 g, 71 %), m.p. 136.5 "C (Found: C, 45.5; H, 2.3; N, 10.1. C5H3F2NO requires C, 45.8; H, 2.3; N, 10.7%); IR spectra no. 23; mass spectra no. 31; nmr spectrum no. 21.
