Name: China Source Factory Supply High Purity 2-Chloro-3-iodopyridine CAS 78607-36-0 with good service
Brand: Wuhan Fortuna Chemical Co., Ltd.

Items	Specifications	Results
Appearance	Off-white solid	Off-white solid
Content(HPLC)	≥98.0%	99.83%
Water content	<0.5%	0.03%
Conclusion	The product up to standard.

2-Chloro-3-iodopyridine is a dihalogenated heterocyclic compound, specifically a pyridine ring substituted with chlorine and iodine atoms at the 2- and 3- positions, respectively.

Core Structure: A pyridine ring, which is a benzene ring with one carbon atom replaced by a nitrogen atom. This nitrogen is electron-withdrawing, making the ring electron-deficient (π-deficient) and influencing its reactivity.
Substituents: It features two different halogen atoms:

A Chlorine (Cl) at the 2-position (ortho to the nitrogen).
An Iodine (I) at the 3-position (meta to the nitrogen).

Key Chemical Properties and Reactivity

The primary chemical significance of 2-Chloro-3-iodopyridine lies in the differential reactivity of its two halogen atoms. This makes it a highly valuable and versatile building block (synthon) in synthetic organic chemistry, particularly for cross-coupling reactions and sequential functionalization.

Halogen	Bond Strength	Innate Reactivity	Common Reactions
Iodine (I)	Weak C-I Bond	High Reactivity	Undergoes oxidative addition with palladium(0) catalysts very easily. It is also more susceptible to nucleophilic substitution.
Chlorine (Cl)	Strong C-Cl Bond	Low Reactivity	Requires specialized catalysts (e.g., XPhos Pd G3) for cross-coupling. It is relatively inert under mild conditions.

This difference in reactivity allows chemists to perform sequential and selective chemical transformations.

1. Selective Cross-Coupling at Iodine

The iodine atom can be selectively functionalized via metal-catalyzed cross-coupling reactions while leaving the chlorine atom untouched. Common reactions include:

Suzuki-Miyaura Reaction: Coupling with boronic acids to install an aryl or vinyl group at the 3-position.
Sonogashira Reaction: Coupling with terminal alkynes to create an alkynyl group at the 3-position.
Heck Reaction: Coupling with alkenes.

These reactions typically use standard palladium catalysts like Pd(PPh₃)₄ or Pd(dba)₂ under mild conditions that do not affect the C-Cl bond.

2. Subsequent Functionalization at Chlorine

After the iodine has been replaced, the resulting 2-chloropyridine derivative can then be subjected to a second round of coupling. This requires harsher conditions or more powerful catalysts designed for challenging C-Cl bond activation (e.g., palladacycle catalysts or specific phosphine ligands like XPhos or SPhos).

Synthetic Utility and Applications

The power of this molecule is its role in modular synthesis. A synthetic chemist can use it to rapidly build complex, disubstituted pyridine structures, which are common scaffolds in:

Pharmaceuticals and Agrochemicals: The pyridine moiety is a privileged structure in drug discovery.
Materials Science: Used in the synthesis of ligands for catalysts and organic electronic materials.

Example Synthetic Sequence:

Start with 2-Chloro-3-iodopyridine.
Perform a Suzuki reaction with phenylboronic acid. This selectively replaces the iodine with a phenyl group, yielding 2-Chloro-3-phenylpyridine.
Perform a second Suzuki reaction (with a more potent catalyst) with a different boronic acid, say, a pyridyl boronic acid. This replaces the chlorine, yielding a complex 2,3-disubstituted pyridine like 3-phenyl-2-(pyridin-3-yl)pyridine.

In summary, 2-Chloro-3-iodopyridine is a strategically designed, bifunctional synthetic building block whose value stems from the orthogonal reactivity of its iodine and chlorine substituents, enabling the controlled, stepwise construction of complex molecules.