4-Chlorothieno[2,3-d]pyrimidine: Properties & Applications

4-chlorothieno[2,3-d]pyrimidine is a bicyclic heteroaromatic building block combining a thiophene ring fused to a pyrimidine core, featuring a reactive C-4 chloro substituent that enables broad utility in the synthesis of pharmacologically active compounds.

Molecular Formula

C₆H₃ClN₂S

Molecular Weight

170.62 g/mol

CAS Number

To be confirmed — see review flag

Key Reactive Site

C-4 chloro group, susceptible to nucleophilic aromatic substitution (SNAr)

Core Scaffold Class

Thienopyrimidine (purine bioisostere)

Primary Application

Medicinal chemistry intermediate for kinase inhibitor and antitumor compound synthesis

Chemical Structure and Properties

4-Chlorothieno[2,3-d]pyrimidine belongs to the thienopyrimidine family of bicyclic heteroaromatic compounds. The molecule consists of a thiophene ring fused at its [2,3-d] positions with a pyrimidine ring, creating a planar, electron-deficient aromatic system. The C-4 position carries a chlorine atom, which significantly activates the ring toward nucleophilic aromatic substitution (SNAr) reactions due to the combined electron-withdrawing effects of the adjacent ring nitrogen atoms.

The compound is typically encountered as a solid at room temperature. Its aromatic bicyclic framework confers reasonable thermal stability, while the C–Cl bond provides a convenient handle for further functionalization under mild to moderate reaction conditions. The thienopyrimidine core is recognized as a classical bioisostere of purine, a property that underpins its widespread use in drug discovery programs targeting nucleotide-binding proteins such as kinases.

Synthesis and Functionalization

4-Chlorothieno[2,3-d]pyrimidine is most commonly prepared from thieno[2,3-d]pyrimidin-4(3H)-one (the corresponding lactam) via chlorination using reagents such as phosphorus oxychloride (POCl₃), often in the presence of a base or catalyst. This route is well-established in heterocyclic chemistry and delivers the chloride in good yield, making it a practical laboratory procedure.

Once in hand, the C-4 chloro group undergoes efficient SNAr reactions with a variety of nucleophiles under mild conditions. Common transformations include:

• Amination: Reaction with primary or secondary amines (aliphatic or aromatic) to furnish 4-aminothieno[2,3-d]pyrimidines, which constitute the largest class of derivatives explored for biological activity.
• Alkoxylation: Treatment with alkoxides to yield 4-alkoxythieno[2,3-d]pyrimidines.
• Thiolation: Reaction with thiols to provide thioether derivatives.
• Transition-metal-catalyzed cross-coupling: Palladium-catalyzed Suzuki–Miyaura, Buchwald–Hartwig, and related couplings extend accessible chemical space further.

The thiophene ring also offers positions (C-5 and C-6) available for electrophilic or directed metalation chemistry, enabling orthogonal diversification of the scaffold.

Research and Medicinal Chemistry Applications

The thienopyrimidine scaffold present in 4-chlorothieno[2,3-d]pyrimidine is well-established as a privileged structure in medicinal chemistry, particularly in the design of protein kinase inhibitors. Kinases require ATP binding, and the purine bioisosteric character of the thienopyrimidine core allows these compounds to compete effectively at the ATP-binding site. Derivatives bearing arylamino or heteroarylamino groups at C-4 have been explored as inhibitors of receptor tyrosine kinases including EGFR, VEGFR, and related targets relevant to oncology research.

Beyond kinase biology, 4-chlorothieno[2,3-d]pyrimidine serves as a key intermediate in the synthesis of compounds with reported antimicrobial, anti-inflammatory, and antiparasitic activities. Its use as a fragment or scaffold in fragment-based drug discovery (FBDD) programs has also been documented in the literature.

In chemical biology, thienopyrimidine derivatives have been employed as tool compounds to probe signaling pathways, making 4-chlorothieno[2,3-d]pyrimidine a valuable reagent for both target-oriented synthesis and broader exploratory chemistry.

Handling, Storage, and Safety Considerations

As with most chlorinated heteroaromatic intermediates, 4-chlorothieno[2,3-d]pyrimidine should be handled with standard laboratory precautions. Personal protective equipment including chemical-resistant gloves, safety glasses, and a laboratory coat should be worn at all times when handling this compound. Operations that may generate dust or aerosols should be conducted in a well-ventilated fume hood.

The compound should be stored in a cool, dry, well-ventilated area away from incompatible materials such as strong oxidizers, strong bases, and moisture. Containers should be kept tightly sealed when not in use to prevent moisture uptake, which can promote hydrolysis of the C–Cl bond over extended periods.

Researchers should consult the current Safety Data Sheet (SDS) provided by Aladdin Scientific for product-specific hazard classifications, first-aid measures, and disposal guidance before use. Waste disposal should comply with applicable local, regional, and national regulations governing the handling of chemical waste.

Product Specification and Ordering Information

Aladdin Scientific offers 4-chlorothieno[2,3-d]pyrimidine (SKU: C173969) to support your research needs. As a supplier of research-grade reagents, Aladdin Scientific is committed to providing consistent purity and reliable supply. Researchers are encouraged to contact our technical support team or visit the product page for current specifications including purity certification, available pack sizes, and pricing.

When ordering, please reference SKU C173969 to ensure accurate fulfillment. Bulk quantities and custom packaging may be available upon request. Our procurement team can assist with institutional purchase orders, quotations, and regulatory documentation as required.

Frequently asked questions

What is the primary use of 4-chlorothieno[2,3-d]pyrimidine in drug discovery?

4-Chlorothieno[2,3-d]pyrimidine is primarily used as a versatile synthetic intermediate in the preparation of thienopyrimidine derivatives, which are extensively studied as protein kinase inhibitors. The C-4 chloro group enables straightforward introduction of amine, alkoxy, or other nucleophilic fragments at this position, allowing rapid access to diverse compound libraries relevant to oncology and other therapeutic areas.

How does the C-4 chloro group of 4-chlorothieno[2,3-d]pyrimidine react with amines?

The C-4 chloro group undergoes nucleophilic aromatic substitution (SNAr) readily with primary and secondary amines due to the electron-deficient nature of the thienopyrimidine ring system. The reaction typically proceeds under mild conditions, often in a polar aprotic solvent or alcohol with optional base assistance, yielding the corresponding 4-aminothieno[2,3-d]pyrimidine products in good to excellent yields.

Is 4-chlorothieno[2,3-d]pyrimidine compatible with palladium-catalyzed cross-coupling reactions?

Yes, the C-4 C–Cl bond can participate in palladium-catalyzed cross-coupling reactions, including Suzuki–Miyaura boronic acid coupling and Buchwald–Hartwig amination. These methods expand the range of substituents accessible at the C-4 position beyond what is achievable by direct SNAr, enabling introduction of aryl, heteroaryl, and additional amino groups under standard cross-coupling conditions.

What storage conditions are recommended for 4-chlorothieno[2,3-d]pyrimidine?

The compound should be stored in a tightly sealed container in a cool, dry, and well-ventilated location, away from moisture, strong oxidizers, and strong bases. Prolonged exposure to moisture can lead to slow hydrolysis of the C–Cl bond. Always consult the current SDS for product-specific storage temperature recommendations and hazard information.

References

1. Comprehensive Heterocyclic Chemistry series — thienopyrimidine chapter. General reference for thienopyrimidine scaffold chemistry and reactivity.
2. General literature on nucleophilic aromatic substitution (SNAr) in electron-deficient heteroaromatics. Standard textbook-level reference.
3. Literature reports on thienopyrimidine-based kinase inhibitors — general class reference for EGFR/VEGFR inhibitor scaffolds. Specific papers not identified; review flag raised.

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