Compound Overview and Properties

4-Chloro-1-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid (Aladdin SKU: C177141) belongs to the pyrazolopyridine class of fused bicyclic heterocycles. The compound integrates a pyrazole ring fused to a pyridine ring, producing a planar, electron-deficient aromatic system that is widely exploited in drug discovery programs.

The N-1 methyl group locks the regiochemistry of the pyrazole nitrogen, eliminating tautomeric ambiguity and conferring improved metabolic stability relative to N-H analogues. The C-4 chloro substituent activates the ring toward nucleophilic aromatic substitution (SNAr), enabling the introduction of amines, thiols, and alkoxides under mild conditions. The C-5 carboxylic acid provides a complementary electrophilic handle for amide bond formation, esterification, and Curtius rearrangement sequences.

These orthogonal reactive sites make the compound a highly efficient bifunctional building block for the construction of complex heterocyclic architectures in one or two synthetic steps.

Storage and Handling Protocol

Storage: Store the compound in a tightly sealed container in a cool (2–8 °C recommended for long-term storage), dry location protected from light and atmospheric moisture. Under these conditions the material is expected to be stable for an extended period; however, actual shelf life should be confirmed by periodic purity testing.

Personal Protective Equipment (PPE): Wear appropriate laboratory coat, chemical-resistant gloves, and safety glasses when handling. Work in a well-ventilated area or fume hood. Although specific toxicological data for this compound are not fully established, treat all novel heterocyclic intermediates with standard chemical hygiene precautions.

Weighing and Transfer: Weigh the solid material in a fume hood using an analytical balance. Use clean, dry spatulas to avoid contamination. Minimize exposure time to ambient humidity, as carboxylic acid-containing heterocycles can be hygroscopic.

Disposal: Dispose of waste material according to local regulations for organic chemical waste. Do not discharge into drains or the environment.

Solubility and Solution Preparation

Recommended Solvents: The compound is expected to show good solubility in polar aprotic solvents such as dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF). Partial solubility may be observed in methanol and ethanol. Solubility in water is typically low for neutral forms of pyrazolopyridine carboxylic acids, but aqueous solubility can be improved by preparing the sodium or potassium salt using one equivalent of base (e.g., NaOH or K₂CO₃).

Stock Solution Preparation:

1. Determine the required concentration and calculate the mass of compound needed based on the molecular weight (refer to the certificate of analysis for confirmed MW and purity).
2. Weigh the compound into a clean, dry glass vial.
3. Add the appropriate volume of DMSO (or chosen solvent) and vortex or sonicate until complete dissolution is achieved.
4. For aqueous reactions, add one equivalent of NaOH or Na₂CO₃ solution to form the carboxylate salt prior to diluting into the aqueous reaction medium.
5. Filter through a 0.2 µm PTFE syringe filter if a particle-free solution is required for biological assays.

Note: Actual solubility values are not confirmed in the source material and should be empirically verified. Flag for review.

Synthetic Applications and Reaction Protocols

The dual-functionality of 4-chloro-1-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid enables a broad range of synthetic transformations:

1. Nucleophilic Aromatic Substitution (SNAr) at C-4

The C-4 chloro group undergoes SNAr with primary and secondary amines, providing 4-amino-substituted pyrazolopyridine derivatives. Typical conditions: amine (1.2–3.0 equiv), base (e.g., Et₃N or K₂CO₃, 2.0 equiv), solvent (DMSO or NMP), temperature 80–120 °C, 4–16 h. Monitor reaction progress by TLC or LCMS.

2. Amide Bond Formation at C-5 Carboxylic Acid

Standard peptide-coupling reagents (e.g., HATU, EDC/HOBt, T3P) facilitate amide bond formation between the carboxylic acid and primary or secondary amines. Typical conditions: carboxylic acid (1.0 equiv), amine (1.1–1.5 equiv), coupling reagent (1.1–1.3 equiv), base (DIPEA or Et₃N, 2–3 equiv), DMF or DCM, room temperature to 60 °C, 2–12 h.

3. Sequential Functionalization

The orthogonal reactivity of the two handles allows sequential modification: perform SNAr first (under basic, high-temperature conditions), then conduct amide coupling on the resulting 4-amino intermediate under mild conditions. This strategy enables efficient library synthesis around the pyrazolopyridine core.

Note: Specific yields, reaction times, and temperatures cited here are textbook-level estimates. Optimization for specific substrates is required. Flag for experimental verification.

Quality Control and Analytical Characterization

Before use in sensitive synthetic or biological applications, confirm the identity and purity of C177141 using the following analytical techniques:

• HPLC Purity: Reverse-phase HPLC (C18 column, UV detection at 254 nm or 280 nm) is recommended to confirm purity. Consult the Aladdin certificate of analysis (CoA) for the batch-specific purity value.
• ¹H NMR: Record in DMSO-d₆ or CDCl₃. Key signals expected: singlet for N-CH₃ (~4.0 ppm), aromatic/heteroaromatic proton signals in the 8–9 ppm region, and a broad carboxylic acid OH signal. Exact chemical shifts should be verified against the CoA or literature.
• Mass Spectrometry: Confirm molecular ion [M+H]⁺ or [M−H]⁻ consistent with the molecular formula by ESI-MS or LCMS. Molecular weight should be confirmed from the CoA.
• Melting Point: Determine melting point as an additional purity indicator and compare against reference values if available.

Note: Specific NMR chemical shift values, exact molecular weight, and melting point are not provided in the source material. Refer to the Aladdin CoA for confirmed analytical data. Flagged for review.