In general, if the atoms that make up the ring contain heteroatoms, such rings become heterocycles, and organic compounds containing heterocycles are called heterocyclic compounds. An article called Aromatic fluorine compounds. IX. 2-Fluoropyridines, published in 1959, which mentions a compound: 2402-95-1, Name is 2-Chloropyridine 1-oxide, Molecular C5H4ClNO, Quality Control of 2-Chloropyridine 1-oxide.
cf. C.A. 53, 13090c. Anhydrous KF (I) 9 g., 12.3 g. 2-chloro-3-nitropyridine and 30 ml. HCONMe2 (DMF) was heated 6 hrs. at 150°, cooled, the mixture poured onto crushed ice, saturated with NaCl, steam distilled, the distillate extracted with Et2O, dried and distilled to give 8.4 g. 2-fluoro-3-nitropyridine, b10 109-9.5° n25D 1.5278. I (73.3 g.) added to a stirred solution of 100 g. 2-chloro-5-nitropyridine and 300 ml DMF at 120°, cooled and processed as above gave 70.1 g. 2-fluoro-5-nitropyridine b7 86-7°, n25D 1.5243. NaNO2 (13.3 g.) in 65 ml. H2O added dropwise with stirring at -2° to 0° to 28 g. 2-amino-3-bromo-5-nitropyridine in aqueous H2SO4 (25%, 900 ml.), the mixture boiled, filtered and cooled gave 18.3 g. 3-bromo-5-nitropyridine (II), m. 212° (decomposition) (H2O). II (4.1 g.), 4 g. PCl3 and 1 ml. POCl3 stirred and refluxed 3 hrs., the mixture concentrated in vacuo and poured onto crushed ice gave 4.2 g. 3-bromo-2-chloro-5-nitropyridine (III), m. 67.3-8.0° after sublimation at 60-70° 2 mm. A stirred mixture of 3.8 g. III, 15 ml. DMF and 1.8 g. I was heated 1 hr. at 100° cooled, poured onto ice, steam distilled, the distillate extracted with Et2O, dried and evaporated to give 2.5 g. crude 3-bromo-2-fluoro-5-nitropyridine; this repeatedly vacuum sublimed gave 1.78 g. pure product, m. 60-1.5° Peracetic acid (40%, 137 ml.) was added dropwise to a stirred solution of 50 g. 2-chloropyridine (IV) and 66 ml. glacial AcOH at 45° the mixture heated 5 hrs. at 50° and 17 hrs. at 70°, concentrated in vacuo to 150 ml. on a steam-bath, poured onto crushed ice, made strongly alk. with 40% NaOH, extracted with CHCl3 dried with MgSO4 and a small amount Na2CO3, the extract evaporated and diluted with 10 ml. anhydrous Et2O gave 45.8 g. 2-chloropyridine N-oxide (V), m. 69-9.5° (Et2O-EtOH). To a mixture obtained by adding 10 g. V to 15 ml. concentrated H2SO4 was added with stirring at 1-2° over 45 min. a mixture of 15 ml. concentrated H2SO4 and 27 ml. fuming HNO3 (sp. gr. 1.5), the mixture heated over 1 hr. to 90°, stirred 1 hr. at 90° cooled to 10° poured onto stirred ice-H2O, neutralized with Na2CO3, filtered, the yellow precipitate partially air dried, dissolved in hot CHCl3, the aqueous filtrate extracted with CHCl3 and the combined CHCl3 solutions dried and evaporated to give 11.4 g. crude 2-chloro-4-nitropyridine N-oxide (VI) m. 153-3.5° (EtOH-CHCl3.) 2-Chloro-4-nitropyridine (VII) was obtained in 91% yield by Hamana procedure (C.A. 50, 1817a). VII (5 g.), 3.7 g. I and 10 ml. di-Me sulfoxide gave a good halide test after being heated 1 hr. at 160°; the mixture was cooled, poured onto crushed ice, saturated with NaCl, steam distilled The distillate was extracted repeatedly with CHCl3; the combined extracts dried and evaporated gave no residue, but the pot residue from the steam distillation gave a small portion of solid, unidentified, m. 100.5-5.0° after sublimation. VII and di-Me sulfoxide in the absence of I gave no evidence of reaction. Dry HCl was passed 2.25 hrs. into a stirred solution of 20 g. IV in 200 ml. anhydrous Et2O and the Et2O evaporated in vacuo to leave 23.4 g. hygroscopic needles, 2-chloropyridine-HCl m. 101.5-2.0°, decomposing on standing, darkening on exposure to light.
Although many compounds look similar to this compound(2402-95-1)Quality Control of 2-Chloropyridine 1-oxide, numerous studies have shown that this compound(SMILES:ClC1=CC=CC=[N+]1[O-]), has unique advantages. If you want to know more about similar compounds, you can read my other articles.
Reference:
Isoxazole – Wikipedia,
Isoxazole | C3H3NO – PubChem