5-Chloro-2-fluoro-4-iodopyridine NEW

5-Chloro-2-fluoro-4-iodopyridine is a synthetic organic compound belonging to the class of halogen-substituted pyridine derivatives. Here's a detailed breakdown of its chemical identity:

Core Structure: Pyridine

• A 6-membered heterocyclic aromatic ring.

• Contains one nitrogen atom (N).

• The carbon atoms in the ring are numbered according to IUPAC rules. The nitrogen is position 1. Adjacent carbons are 2 and 6 (equivalent), followed by 3 and 5 (equivalent), and the carbon opposite nitrogen is position 4.

  Substituents (Halogens):

• Chloro (Cl): Attached to the carbon at position 5.

• Fluoro (F): Attached to the carbon at position 2.

• Iodo (I): Attached to the carbon at position 4.

  Chemical Formula: C₅H₂ClFIN

• Represents the elemental composition: 5 Carbon (C), 2 Hydrogen (H), 1 Chlorine (Cl), 1 Fluorine (F), 1 Iodine (I), 1 Nitrogen (N).

  Molecular Weight: 285.43 g/mol

• Calculated as: (5×12.01) + (2×1.008) + 35.45 + 19.00 + 126.90 + 14.01 = 285.43 g/mol.

  CAS Registry Number: 1020719-94-8

• A unique numerical identifier assigned to this specific chemical by the Chemical Abstracts Service (CAS).

Key Structural Features:

• Iodine (Position 4): Most reactive in Pd-catalyzed cross-coupling.

• Fluorine (Position 2): Highly reactive in nucleophilic aromatic substitution (SNAr).

• Chlorine (Position 5): Least reactive of the three, requires harsher conditions for substitution or coupling.

• Multiple Halogens: Possesses three different halogens (F, Cl, I) at specific positions (2, 5, 4).

• Position 2 & 4: Positions adjacent (ortho) or opposite (para) to the ring nitrogen are inherently more electron-deficient and thus more reactive towards nucleophilic aromatic substitution (SNAr). The 2-fluoro group is particularly activated for SNAr due to the ortho-nitrogen.

• Position 4 (Iodo): The iodine atom is an excellent leaving group for transition metal-catalyzed cross-coupling reactions (e.g., Suzuki, Stille, Negishi).

• Position 5 (Chloro): While less reactive than iodine in cross-coupling, the chlorine can participate under appropriate conditions (e.g., Buchwald-Hartwig amination with strong ligands/high temperatures) or serve as a site for further functionalization after the more reactive sites are modified.

• Reactivity Hierarchy: The halogens exhibit different reactivities allowing for selective sequential functionalization:

  Synonyms (Common Names/Labels):

• 5-Chloro-2-fluoro-4-iodopyridine (Systematic name, most common)

• 4-Iodo-5-chloro-2-fluoropyridine

• 2-Fluoro-5-chloro-4-iodopyridine

• Pyridine, 5-chloro-2-fluoro-4-iodo- (CAS format)

• Often abbreviated in chemical vendor catalogs simply by its substitution pattern (e.g., "2F,5Cl,4I-Pyridine").

In Summary:
5-Chloro-2-fluoro-4-iodopyridine is a multifunctional heterocyclic building block characterized by a pyridine ring substituted with three distinct halogens (F, Cl, I) at positions 2, 5, and 4. Its chemical identity is defined by its molecular formula (C₅H₂ClFIN), molecular weight (285.43 g/mol), CAS number (1020719-94-8), and its specific substitution pattern which dictates its unique reactivity profile, making it a valuable intermediate in synthetic organic chemistry, particularly medicinal chemistry.