2,6-Dihydroxy-3-cyanopyridine: Handling & Application Protocol

2,6-Dihydroxy-3-cyanopyridine is a versatile hydroxypyridine building block widely employed as a synthetic intermediate in the preparation of heterocyclic compounds, coordination ligands, and pharmacologically relevant scaffolds.

CAS Number

1194-37-2

Molecular Formula

C6H4N2O2

Molecular Weight

136.11 g/mol

Appearance

Off-white to pale yellow solid powder

Recommended Storage

Store in a cool, dry place away from light; seal tightly after use

SKU

D192953

Overview and Chemical Properties

2,6-Dihydroxy-3-cyanopyridine (CAS 1194-37-2) is a pyridine derivative bearing hydroxyl groups at the 2- and 6-positions and a nitrile (cyano) substituent at the 3-position. In solution and solid state, the compound predominantly exists in the lactam (pyridone) tautomeric form, giving it the character of 3-cyano-1H-pyridine-2,6(1H,5H)-dione. This dual functionality—two carbonyl-like donor sites and a reactive nitrile group—makes it a highly useful heterocyclic building block for further chemical transformations, including nucleophilic addition, cyclocondensation, and metal coordination chemistry.

Molecular formula: C₆H₄N₂O₂; MW: 136.11 g/mol. The compound is sparingly soluble in water and common apolar solvents, but dissolves in polar aprotic solvents such as DMSO and DMF, and in dilute aqueous base.

Safety and Handling Precautions

Before working with 2,6-Dihydroxy-3-cyanopyridine, consult the current Safety Data Sheet (SDS) supplied by Aladdin Scientific. Observe the following general precautions:

• Personal Protective Equipment (PPE): Wear nitrile gloves, a laboratory coat, and safety glasses at all times. Use a fume hood when weighing or preparing solutions to minimize inhalation of dust or vapors.
• Skin and Eye Contact: Avoid direct contact. In case of skin contact, wash thoroughly with soap and water. For eye contact, rinse immediately with copious water for at least 15 minutes and seek medical attention.
• Inhalation: Do not inhale dust or aerosols. Work in a well-ventilated area or fume hood.
• Waste Disposal: Dispose of all waste in accordance with local, regional, and national regulations for chemical waste containing nitrogen heterocycles.
• Incompatibilities: Avoid contact with strong oxidizing agents, strong acids, and strong bases, which may cause decomposition or unwanted reactions at the nitrile or hydroxyl groups.

Solution Preparation Protocol

The following protocol describes preparation of a stock solution suitable for synthetic or analytical use. Adjust scale as required.

1. Determine target concentration. For most synthetic applications, a 10–100 mM stock solution in DMSO or DMF is suitable. For aqueous assays requiring basic conditions, prepare a solution in 0.1 M NaOH (aq) and neutralize cautiously before use.
2. Calculate mass required. Use the formula: mass (mg) = concentration (mM) × volume (mL) × MW (g/mol) × 10⁻³. Example: for 10 mM in 10 mL DMSO — mass = 10 × 10 × 136.11 × 10⁻³ = 13.61 mg.
3. Weigh accurately. Tare a clean, dry microcentrifuge tube or glass vial on an analytical balance. Add the calculated mass of 2,6-Dihydroxy-3-cyanopyridine (SKU: D192953). Record the actual mass.
4. Add solvent. Pipette the calculated volume of DMSO (or DMF) into the vessel. For improved dissolution, warm gently to 37–40 °C in a water bath with occasional vortexing. Do not exceed 60 °C.
5. Verify dissolution. The solution should be clear to very slightly yellow. If particulates remain, centrifuge briefly (2 000 × g, 2 min) and use the supernatant.
6. Aliquot and store. Divide into single-use aliquots under inert atmosphere (N₂ or Ar) if long-term stability is required. Store at −20 °C, protected from light and moisture. Note preparation date and concentration on each vial.

Note: Avoid repeated freeze-thaw cycles, which may promote hydrolysis of the nitrile group over extended periods.

Representative Applications in Synthesis

2,6-Dihydroxy-3-cyanopyridine serves as a multifunctional precursor in heterocyclic synthesis. Key documented applications include:

• Cyclocondensation reactions: The active methylene or enamine equivalents generated under basic conditions allow ring-closure reactions with bifunctional electrophiles to yield fused pyridopyrimidines, naphthyridines, and related polycyclic systems.
• Nitrile hydrolysis and derivatization: Under controlled acidic or basic aqueous conditions, the cyano group can be hydrolyzed to the corresponding carboxamide or carboxylic acid, providing 2,6-dihydroxynicotinamide or 2,6-dihydroxynicotinic acid as intermediates for further elaboration.
• Metal coordination chemistry: The pyridone nitrogen and carbonyl oxygens act as chelating donor atoms, enabling use of this scaffold in the design of metal complexes for catalysis or materials science applications.
• Pharmaceutical intermediate: 3-Cyanopyridine and hydroxypyridine motifs appear in bioactive molecules; this compound may serve as a starting material for libraries targeting enzyme inhibition or receptor binding studies.

Researchers should validate each application with appropriate controls and confirm purity of the starting material by HPLC or NMR prior to use.

Quality Control and Troubleshooting

Purity verification: Before use in sensitive applications, confirm identity and purity by ¹H NMR (key signals: aromatic/vinyl protons 6.0–8.5 ppm region; NH broad signal) and by reverse-phase HPLC (C18 column, UV detection at 254 nm or 280 nm). Aladdin Scientific provides lot-specific CoA data; cross-check your results against the supplied specification.

Common issues and solutions:

• Poor dissolution: Warm the solvent to 40 °C and sonicate for 5–10 min. If using aqueous media, add a minimum volume of 0.1 M NaOH to assist dissolution, then dilute to working concentration.
• Yellow discoloration of solution: A pale yellow color is normal; deep orange or brown discoloration may indicate oxidative degradation. Use fresh solvent and work under inert atmosphere.
• Unexpected reaction outcomes: Confirm tautomeric form present under your reaction conditions. At neutral to acidic pH, the pyridone form predominates; under strongly basic conditions, the phenolate (dianionic) form may be present and exhibit different reactivity.
• Low yield in cyclocondensation: Optimize base equivalents (typically 1–2 equiv. K₂CO₃ or Et₃N) and reaction temperature. Ensure exclusion of moisture when using DMF as solvent.

Frequently asked questions

What solvents are recommended for dissolving 2,6-Dihydroxy-3-cyanopyridine?

DMSO and DMF are the preferred solvents for preparing stock solutions due to the compound's limited aqueous solubility. For aqueous systems, dissolution in dilute NaOH (0.1 M) followed by pH adjustment is an alternative approach. Avoid strongly acidic aqueous conditions, which may promote nitrile hydrolysis.

How should 2,6-Dihydroxy-3-cyanopyridine be stored to maintain stability?

Store the solid compound in a tightly sealed container in a cool, dry place protected from light, ideally at 2–8 °C or −20 °C for long-term storage. Stock solutions in DMSO should be aliquoted under inert atmosphere and stored at −20 °C to minimize degradation. Avoid repeated freeze-thaw cycles.

In which tautomeric form does 2,6-Dihydroxy-3-cyanopyridine predominantly exist?

The compound predominantly exists in the bis-lactam (pyridone) tautomeric form rather than the bis-hydroxypyridine form, both in the solid state and in most solvents. This tautomeric preference has implications for its reactivity profile; under strongly basic conditions, deprotonation yields the dianion, which may exhibit different nucleophilic or coordination behavior.

Is 2,6-Dihydroxy-3-cyanopyridine suitable for use as a metal chelating ligand?

Yes, the pyridone nitrogen and adjacent carbonyl oxygens provide potential binding sites for transition metal ions, making this scaffold relevant in coordination chemistry. However, the specific stability constants and preferred coordination modes for any particular metal should be determined experimentally, as these values are not universally established in the literature for this exact compound.

What analytical methods are recommended to confirm purity before use?

Reverse-phase HPLC with UV detection at 254 or 280 nm and 1H NMR spectroscopy are the recommended orthogonal techniques for purity and identity confirmation. Aladdin Scientific provides a Certificate of Analysis (CoA) with each lot; compare your in-house analytical data against the CoA specifications to confirm suitability for your application.

References

1. Aladdin Scientific. Product page and Certificate of Analysis for 2,6-Dihydroxy-3-cyanopyridine, SKU D192953. Accessed 2024.
2. Elguero, J.; Marzin, C.; Katritzky, A. R.; Linda, P. The Tautomerism of Heterocycles. Advances in Heterocyclic Chemistry, Supplement 1. Academic Press, 1976.
3. Comprehensive Organic Transformations, Larock, R. C., 2nd ed., Wiley-VCH, 1999. Chapter on nitrile hydrolysis and heterocyclic synthesis.

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.