3-Bromo-6,7-dihydro-5H-cyclopenta[B]pyridin-5-one
[CAS# 1196154-87-6]

Identification

• Classification: Pharmaceutical intermediate >> Heterocyclic compound intermediate >> Pyridine compound
• Name: 3-Bromo-6,7-dihydro-5H-cyclopenta[B]pyridin-5-one
• Molecular Formula: C₈H₆BrNO
• Molecular Weight: 212.04
• CAS Registry Number: 1196154-87-6
• SMILES: C1CC(=O)C2=C1N=CC(=C2)Br

Properties

• Density: 1.7±0.1 g/cm³, Calc.^*
• Index of Refraction: 1.631, Calc.^*
• Boiling Point: 291.1±40.0 ºC (760 mmHg), Calc.^*
• Flash Point: 129.8±27.3 ºC, Calc.^*

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

Safety Data

• Hazard Symbols: GHS07 Warning
• Hazard Statements: H302
• Precautionary Statements: P280-P305+P351+P338

Discovory and Applicatios

3-Bromo-6,7-dihydro-5H-cyclopenta[b]pyridin-5-one (CAS 1196154-87-6) is a bicyclic heterocyclic compound comprising a cyclopenta[b]pyridin-one core with a bromine atom at the 3-position, and two added hydrogens on the 6,7-positions (yielding the dihydro form). The molecular formula is C₈H₆BrNO and the molecular weight is approximately 212.05 g/mol. The bicyclic structure places the nitrogen atom of the pyridine ring adjacent to the five-membered cyclopentane ring, establishing a fused heterocycle. The presence of the bromine substituent at the 3-position provides a handle for further functionalisation via cross-coupling or nucleophilic substitution reactions.

This compound is primarily described in chemical supplier catalogues as a building block or intermediate in organic synthesis, especially in medicinal chemistry and heterocyclic chemistry workflows. It is used as a reagent for the construction of more complex heterocyclic scaffolds through reactions such as palladium-catalysed cross-coupling, nucleophilic aromatic substitution of the bromine, or reduction and functional group transformation of the ketone (pyridinone) core. The 5H-cyclopenta[b]pyridin-5-one nucleus is a structurally constrained heterocycle, offering rigid and nearly planar geometry that is favourable in the design of biologically active molecules where defined conformation is required.

Because the compound incorporates a ketone functionality adjacent to a heterocyclic nitrogen, the pyridinone ring exhibits tautomeric and hydrogen-bonding behaviour, which can influence its chemical reactivity and physical properties such as solubility and crystal packing. The bromine substituent at the 3-position increases the compound’s electrophilicity at that site and allows derivatisation via Suzuki, Buchwald–Hartwig or other cross coupling reactions to introduce aryl, heteroaryl or alkyl substituents, enabling exploration of structure-activity relationships in medicinal chemistry libraries. Although specific biological activities for this exact compound are not widely published, the 3-bromo substitution pattern on bicyclic heterocycles is often employed to generate novel derivatives for screening as kinase inhibitors, receptor ligands or other bioactive small molecules.

In the laboratory context, the compound is available at high purity (e.g., 98 %) and is stored sealed under dry conditions to prevent moisture-induced degradation. Handling involves typical organic chemistry precautions for brominated heterocycles, including avoidance of strong nucleophiles that might cause debromination and protection from prolonged light exposure, which might induce photolysis of the brominated ring system. Its solubility characteristics reflect its heterocyclic, polar but partially aromatic nature: moderate solubility in polar aprotic solvents (e.g., dimethyl sulfoxide, DMF) and lower solubility in non-polar solvents.

In summary, 3-Bromo-6,7-dihydro-5H-cyclopenta[b]pyridin-5-one is a niche organic intermediate useful for synthetic chemistry applications, especially in heterocycle functionalisation. It offers a structurally rigid bicyclic system with a reactive bromine leaving group and a ketone/heterocycle motif that can serve as a platform for medicinal chemistry explorations and structural derivatisation.