2-Bromo-1H-indole-3-carbaldehyde

This compound is typically isolated as a crystalline solid ranging from pale yellow to light brown. Its molecular formula is C9H6BrNO, corresponding to a molecular weight of 224.05. The melting point generally exceeds 225 °C, often with decomposition observed upon prolonged heating. The calculated density is approximately 1.78 g/cm³ under ambient conditions. It exhibits moderate solubility in polar organic solvents such as dimethyl sulfoxide and dimethylformamide, limited solubility in ethyl acetate and methanol, and negligible solubility in water and nonpolar solvents like dichloromethane and hexane. The molecule consists of an indole ring system with a bromine atom at the 2position and an aldehyde group at the 3position. The indole NH is acidic and can participate in hydrogen bonding, while the aldehyde is susceptible to condensation and oxidation reactions. The bromine atom is activated toward crosscoupling by the electronrich nature of the indole ring. Storage in tightly sealed amber containers under inert atmosphere at reduced temperature (2–8 °C) is recommended to prevent lightinduced degradation and oxidation. Contact with strong oxidizing agents, strong bases, and reducing agents should be avoided.

2Bromo1Hindole3carbaldehyde is a bifunctional indole derivative featuring both a halogen and a formyl group on the fused heteroaromatic scaffold. The indole nucleus, consisting of a benzene ring fused to a pyrrole ring, provides a rigid, electronrich platform capable of engaging in πstacking interactions and hydrogen bonding through the NH group. The bromine atom at the 2position is activated toward nucleophilic substitution and palladiumcatalyzed crosscoupling reactions due to its proximity to the pyrrole nitrogen. The aldehyde at the 3position offers an electrophilic handle for reductive amination, condensation with amines or hydrazines, and oxidation to the corresponding carboxylic acid. The proximity of the two substituents enables the construction of fused heterocyclic systems through intramolecular cyclization reactions. This combination of a versatile halogen and a reactive carbonyl on a privileged heteroaromatic core makes the compound a valuable building block in medicinal chemistry and materials science for constructing diverse indolebased libraries.

Pharmaceutical Intermediate
In drug discovery, this bromoindole aldehyde is employed as a key building block for synthesizing kinase inhibitors and other therapeutic agents. The bromine enables Suzuki–Miyaura couplings with boronic acids to introduce diverse aryl or heteroaryl groups at the 2position, while the aldehyde allows reductive amination to incorporate basic amine side chains or condensation to form hydrazone pharmacophores. Indole derivatives prepared from this scaffold have shown promise in targeting cancer, inflammation, and neurological disorders, where the indole core contributes to binding through hydrogen bonding and πstacking interactions.

Anticancer Research
Derivatives of this compound have demonstrated cytotoxic activity against various cancer cell lines through mechanisms involving apoptosis induction and cell cycle arrest. The ability to modulate both the bromine and aldehyde positions enables systematic exploration of structureactivity relationships for optimizing potency and selectivity against tumor cells while minimizing offtarget effects.

Antimicrobial Agent Development
The scaffold has been investigated for its antimicrobial properties, with derivatives showing activity against methicillinresistant Staphylococcus aureus and other clinically relevant pathogens. The electronrich indole core can interact with bacterial enzymes and DNA, while substituents introduced via the bromine handle can enhance membrane penetration and target affinity, providing opportunities for developing new antibiotics to combat drug resistance.

Organic Synthesis Building Block
As a versatile synthetic intermediate, 2bromo1Hindole3carbaldehyde participates in diverse transformations including palladiumcatalyzed crosscouplings, nucleophilic aromatic substitution, and condensation reactions. The aldehyde can be converted to alcohols, carboxylic acids, or imines for further elaboration. The proximity of the two functional groups enables intramolecular cyclization to access fused heterocyclic systems such as pyrido[3,4b]indoles and indolo[2,3c]quinolines. Its utility extends to the synthesis of natural product analogs and functional materials where the indole ring imparts desirable electronic and structural properties.