2,4-Dichloropyrrolo[2,1-f][1,2,4]triazine
[CAS 918538-05-3]

Identification

• Classification: Organic raw materials >> Heterocyclic compound >> Triazines
• Name: 2,4-Dichloropyrrolo[2,1-f][1,2,4]triazine
• Molecular Formula: C₆H₃Cl₂N₃
• Molecular Weight: 188.01
• CAS Registry Number: 918538-05-3
• EC Number: 876-119-4
• SMILES: C1=CN2C(=C1)C(=NC(=N2)Cl)Cl

Properties

• Density: 1.7$+/-$0.1 g/cm³ Calc.^*
• Index of refraction: 1.733 (Calc.)^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H319-H335
• Safety Statements: P261-P305+P351+P338

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2A	H319
Specific target organ toxicity - single exposure	STOT SE	3	H335
Skin irritation	Skin Irrit.	2	H315
Acute toxicity	Acute Tox.	4	H302

Discovery and Applications

2,4-Dichloropyrrolo[2,1-f][1,2,4]triazine is a heterocyclic compound featuring a fused pyrrole and triazine ring system, with chlorine atoms substituted at the 2- and 4-positions of the triazine moiety. This molecular arrangement combines the electron-rich pyrrole ring with an electron-deficient triazine core, and the chlorines increase electrophilicity at specific positions, making the compound a useful intermediate in pharmaceutical and agrochemical synthesis.

The molecular structure consists of a five-membered pyrrole ring fused to a six-membered triazine ring, forming a planar bicyclic system. The chlorine atoms at positions 2 and 4 on the triazine ring enhance the molecule’s reactivity toward nucleophilic substitution reactions, allowing functionalization with various amines, thiols, or other nucleophiles. The fused heterocycle provides rigidity and electronic conjugation, which can influence biological activity and chemical stability.

Synthesis of 2,4-dichloropyrrolo[2,1-f][1,2,4]triazine typically involves cyclization of appropriately substituted amino pyrrole derivatives with cyanamide or related triazine precursors, followed by selective chlorination at the 2- and 4-positions. Reaction conditions are carefully controlled to prevent over-chlorination or undesired side reactions, and high-purity products are essential for use in subsequent transformations.

The main application of this compound is as an intermediate in the preparation of pharmacologically active molecules. Its electrophilic chlorinated positions allow substitution with nucleophilic reagents to construct derivatives with potential antiviral, anticancer, or enzyme-inhibiting properties. It is also used in the synthesis of agrochemicals where fused heterocycles with controlled substitution patterns confer stability and bioactivity.

Additionally, 2,4-dichloropyrrolo[2,1-f][1,2,4]triazine serves as a building block for heterocyclic libraries in medicinal chemistry, enabling the exploration of structure-activity relationships in drug discovery. Its combination of an electron-rich pyrrole and electron-deficient triazine ring allows tuning of electronic properties and solubility through further functionalization.

Overall, 2,4-dichloropyrrolo[2,1-f][1,2,4]triazine is a reactive and versatile heterocyclic intermediate. Its fused pyrrole-triazine system with chlorinated positions provides opportunities for nucleophilic substitution, making it valuable in the synthesis of pharmaceuticals, agrochemicals, and heterocyclic derivatives for research applications.

References

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2023. Parp inhibitors and uses thereof. WO-2025092905-A1.
URL: https://patents.google.com/patent/WO2025092905A1/en