Compound Overview and Structural Features

3-Bromo-4-methoxy-1H-pyrazolo[3,4-d]pyrimidine belongs to the pyrazolopyrimidine class of fused bicyclic heterocycles, in which a five-membered pyrazole ring is annulated to a six-membered pyrimidine ring via shared C-3a and C-7a atoms (using pyrazolopyrimidine numbering). This scaffold is bioisosteric with purines, making it a privileged framework in medicinal chemistry.

The compound carries two orthogonal reactive handles: a bromine atom at C-3 and a methoxy group at C-4. The C-3 bromine is an aryl bromide suitable for palladium-catalyzed cross-coupling reactions, while the C-4 methoxy group acts as a leaving group under nucleophilic aromatic substitution (S_NAr) conditions, particularly with primary and secondary amines. This dual functionality allows sequential and selective diversification of the scaffold in multi-step synthesis workflows.

The NH tautomer at N-1 is typical for 1H-pyrazolopyrimidines and can be alkylated or acylated to introduce N-substituents, providing a third site for structural elaboration.

Synthetic Utility and Reaction Chemistry

Palladium-catalyzed cross-coupling at C-3: The aryl bromide at C-3 is well-suited for a range of Pd(0)/Pd(II)-mediated transformations. Suzuki–Miyaura coupling with aryl- and heteroarylboronic acids installs carbon substituents with high efficiency. Buchwald–Hartwig amination allows introduction of aryl- and diarylamino groups. Sonogashira coupling with terminal alkynes and Negishi coupling with organozinc reagents are also feasible, giving access to diverse C-3-substituted analogs.

Nucleophilic displacement at C-4: The 4-methoxy group is activated toward S_NAr by the electron-deficient pyrimidine ring nitrogen atoms. Treatment with primary or secondary amines under mild heating conditions (typically 60–100 °C in polar aprotic or protic solvents) replaces the methoxy group to furnish 4-amino derivatives, a common pharmacophore motif in kinase inhibitors. Alkoxide nucleophiles can similarly be employed to produce 4-alkoxy analogs.

N-1 functionalization: The pyrazole N-H can be deprotonated with mild base (e.g., K₂CO₃) and alkylated with alkyl halides or reacted with acyl chlorides to yield N-1-substituted products, enabling introduction of solubilizing or targeting groups.

These complementary reactivities make 3-bromo-4-methoxy-1H-pyrazolo[3,4-d]pyrimidine a highly efficient three-point diversification template for library synthesis.

Research Applications in Drug Discovery

The pyrazolo[3,4-d]pyrimidine scaffold is recognized as a purine bioisostere and has been extensively explored in the design of kinase inhibitors, particularly those targeting the ATP-binding site. Because kinase active sites are evolutionarily conserved and optimized to bind the purine ring of ATP, purine-mimicking heterocycles such as pyrazolopyrimidines are effective starting points for inhibitor design.

Derivatives of 3-bromo-4-methoxy-1H-pyrazolo[3,4-d]pyrimidine have been employed as intermediates in the synthesis of compounds targeting tyrosine kinases, cyclin-dependent kinases (CDKs), and phosphoinositide 3-kinases (PI3Ks), among others. The 4-amino substitution pattern obtained by S_NAr is particularly common in clinical and preclinical kinase inhibitor candidates.

Beyond kinase biology, the scaffold has been explored in antiviral, antiparasitic, and anti-inflammatory contexts, reflecting the broad utility of the pyrazolopyrimidine core in medicinal chemistry programs. The compound is therefore of interest to research groups working in oncology, infectious disease, and immunology.

In fragment-based drug discovery (FBDD) and high-throughput screening (HTS) library design, bifunctional building blocks such as B175349 are valued for their ability to rapidly generate structurally diverse analogs from a single starting material.

Handling, Storage, and Quality Considerations

Storage: Pyrazolopyrimidine building blocks are generally stable when stored as solids under cool, dry conditions. To maximize shelf life, B175349 should be stored in a tightly sealed container away from moisture and light, at the temperature specified on the product certificate of analysis (CoA). Refrigerated storage (2–8 °C) is commonly appropriate for such heterocyclic intermediates.

Handling: Standard laboratory precautions for handling organic bromides and heterocyclic compounds should be observed. Use of appropriate personal protective equipment (PPE) including gloves, lab coat, and eye protection is recommended. Operations generating dust or aerosols should be conducted in a fume hood.

Solubility: The compound is expected to dissolve in common polar organic solvents such as DMSO, DMF, and acetonitrile, which are typical choices for stock solution preparation in biological assays and synthetic reactions. Aqueous solubility is likely limited due to the lipophilic methoxy and bicyclic aromatic character of the molecule.

Purity: For synthetic and biological applications, purity of the starting material is critical. Researchers should consult the CoA provided with each lot for confirmed purity data (typically assessed by HPLC and/or NMR). Any lot-specific specifications supersede general information.

Stability note: The methoxy group at C-4 renders this position susceptible to nucleophilic attack under strongly basic or nucleophilic conditions even in the absence of deliberate reaction conditions; avoid prolonged exposure to concentrated amines or strong bases in solution.