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 Some 2,5- and 5,6-dihalonicotinic acids and their precursors. IV, published in 1976, which mentions a compound: 59782-89-7, Name is 2-Chloro-5-iodo-3-methylpyridine, Molecular C6H5ClIN, Quality Control of 2-Chloro-5-iodo-3-methylpyridine.
The pyridinecarboxylic acids I (R = Cl, R1 = CO2H, R2 = Cl, iodo; R = Cl, R1 = Cl, iodo, R2 = CO2H) were prepared by oxidation of I (R = Cl, R1 = Me, R2 = Cl, iodo; R = Cl, R1 = Cl, iodo, R2 = Me; resp.), which were prepared by diazotization and substitution of I (R = Cl, R1 = Me, R2 = NH2; R = Cl, R1 = NH2, R2 = Me; resp.). I (R = R1 = Cl, R2 = CO2H) and NaI gave I (R = iodo, R1 = Cl, R2 = CO2H).
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Reference:
Pyrroline – Wikipedia,
1-Pyrroline | C4H7N – PubChem