3-Chloroquinoxalin-2-amine: Properties, Synthesis & Applications

3-chloroquinoxalin-2-amine is a halogenated bicyclic heterocyclic compound featuring both a reactive chloro substituent and a primary amino group on the quinoxaline ring system, making it a highly versatile intermediate for medicinal chemistry and materials science research.

CAS Number

Not specified in source material

Molecular Formula

C8H6ClN3

Molecular Weight

179.61 g/mol

Core Structure

Quinoxaline bicyclic ring system with Cl at C-3 and NH2 at C-2

Key Functional Groups

Primary amine (-NH2) and aryl chloride (C-Cl)

Primary Use

Synthetic intermediate and building block in pharmaceutical and heterocyclic chemistry

Chemical Identity and Structural Features

3-Chloroquinoxalin-2-amine belongs to the quinoxaline family of nitrogen-containing bicyclic heterocycles. The quinoxaline scaffold consists of a benzene ring fused with a pyrazine ring, resulting in a planar aromatic system. In 3-chloroquinoxalin-2-amine, a chlorine atom occupies position 3 and a primary amino group (-NH2) is located at position 2 of the quinoxaline ring.

This combination of functional groups is chemically significant. The electron-withdrawing nature of the ring nitrogens activates the C-3 chloro substituent toward nucleophilic aromatic substitution (SNAr), enabling efficient displacement by amines, thiols, alkoxides, and other nucleophiles under mild conditions. Simultaneously, the C-2 amino group can participate in condensation reactions, acylation, and cyclization chemistry, offering two orthogonal handles for further derivatization. The molecular formula is C8H6ClN3 with a molecular weight of approximately 179.61 g/mol.

Synthesis and Preparation Routes

3-Chloroquinoxalin-2-amine is commonly prepared from readily available quinoxaline precursors. A classical approach involves the halogenation of quinoxalin-2-amine or the selective chlorination of dihydroquinoxalinedione derivatives followed by functional group manipulation. Alternatively, reaction of o-phenylenediamine with appropriate α-haloketone or diketone equivalents can provide substituted quinoxalines that are subsequently chlorinated at specific ring positions.

Another practical route involves the reaction of chloroacetyl chloride or related chlorinated reagents with o-phenylenediamine derivatives, followed by oxidation and tautomer control steps to install the amino and chloro groups regioselectively. The resulting compound is typically purified by recrystallization or column chromatography to meet research-grade purity requirements. As a commercial reagent supplied by Aladdin Scientific (SKU: C176181), 3-chloroquinoxalin-2-amine is available ready-to-use, bypassing multi-step in-house synthesis.

Research Applications and Biological Relevance

Quinoxaline derivatives bearing amino and halo substituents have attracted sustained interest in medicinal chemistry owing to the broad biological activity profile associated with this scaffold. Compounds incorporating the quinoxalin-2-amine framework have been investigated as potential kinase inhibitors, antimicrobial agents, antitumor candidates, and modulators of various enzyme targets. The simultaneous presence of the amine and the chloro group in 3-chloroquinoxalin-2-amine allows researchers to rapidly generate structurally diverse analogue libraries through parallel synthesis.

In materials science, quinoxaline-based compounds are explored as components of organic semiconductors, fluorescent probes, and coordination complexes with transition metals. The amino group in 3-chloroquinoxalin-2-amine can act as a ligand donor, enabling chelation with metal centers for catalytic or photophysical applications. As a bifunctional building block, it is widely employed in the construction of fused heterocyclic systems such as imidazo[1,2-a]quinoxalines and related ring systems via condensation with bifunctional partners.

Handling, Storage, and Safety Considerations

As with most halogenated aromatic amines, 3-chloroquinoxalin-2-amine should be handled with appropriate laboratory precautions. Aromatic amines as a chemical class may present sensitization or toxic hazard potential; researchers should consult the Safety Data Sheet (SDS) provided by Aladdin Scientific before use. Standard personal protective equipment (PPE) including chemical-resistant gloves, laboratory coat, and eye protection is recommended.

The compound should be stored in a tightly sealed container, protected from moisture and light, in a cool and dry environment consistent with general guidance for halogenated heterocyclic intermediates. Long-term stability is best maintained at controlled room temperature or under refrigeration as specified in the product SDS. Avoid contact with strong oxidizing agents and strong bases. Waste disposal should follow applicable local regulations for halogenated organic compounds.

Reactivity and Key Transformations

The dual functionality of 3-chloroquinoxalin-2-amine enables a rich array of synthetic transformations. The C-3 chloro group undergoes nucleophilic aromatic substitution (SNAr) with primary and secondary amines to yield 2-amino-3-(alkylamino)quinoxalines, which are important scaffolds in drug discovery. Reaction with thiols gives thioether-linked products, while alkoxide nucleophiles afford ether derivatives.

The primary amino group at C-2 is amenable to diazotization under cold acidic conditions, opening access to azo dyes and halogenated quinoxalines via Sandmeyer-type reactions. Acylation of the amine with acid chlorides or anhydrides furnishes amide derivatives useful as further intermediates. Additionally, palladium-catalyzed cross-coupling reactions (e.g., Buchwald–Hartwig amination, Suzuki–Miyaura coupling) at the C-3 chloro position can be employed to introduce aryl or amino groups under mild conditions, expanding the accessible chemical space substantially.

Frequently asked questions

What makes 3-chloroquinoxalin-2-amine useful as a synthetic building block?

3-Chloroquinoxalin-2-amine possesses two orthogonal reactive sites: a C-3 aryl chloride susceptible to nucleophilic aromatic substitution and palladium-catalyzed cross-coupling, and a C-2 primary amine available for condensation, acylation, and diazotization. This dual reactivity allows medicinal and synthetic chemists to rapidly diversify the compound into a wide range of quinoxaline-based derivatives from a single starting material.

How should 3-chloroquinoxalin-2-amine be stored to maintain stability?

The compound should be stored in a tightly sealed container in a cool, dry location, protected from light and moisture. Refrigerated storage may be recommended for extended shelf life. Always refer to the Aladdin Scientific SDS (for SKU C176181) for specific storage temperature and handling instructions applicable to your purchased lot.

Is 3-chloroquinoxalin-2-amine suitable for kinase inhibitor research?

Quinoxaline derivatives bearing amino and halogen substituents have been widely explored as kinase inhibitor scaffolds in medicinal chemistry research. The amino and chloro groups of 3-chloroquinoxalin-2-amine provide handles for generating diverse analogues that can be screened for kinase inhibitory activity. However, researchers should validate biological activity experimentally for any specific target, as activity will depend on the final derivative structure.

Can the C-3 chloro group of 3-chloroquinoxalin-2-amine participate in palladium-catalyzed cross-coupling?

Yes. The aryl chloride at C-3 of the quinoxaline ring is electronically activated by the adjacent ring nitrogens, making it a competent electrophilic partner in palladium-catalyzed reactions such as Suzuki–Miyaura coupling and Buchwald–Hartwig amination. Appropriate ligand selection is important to achieve good reactivity with aryl chloride substrates under these conditions.

References

1. Comprehensive Heterocyclic Chemistry (Elsevier) — Quinoxalines chapter; general reference for quinoxaline chemistry and reactivity.
2. March's Advanced Organic Chemistry — Nucleophilic Aromatic Substitution and Cross-Coupling sections; textbook-level reference for SNAr and palladium-catalyzed reactions.
3. Aladdin Scientific product page for 3-chloroquinoxalin-2-amine, SKU C176181.

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.