Overview and Chemical Properties

5-Formylfuran-2-boronic acid, pinacol ester (SKU: F733265) is a bifunctional organoboron reagent that combines a furan aromatic core with two synthetically valuable handles: a 5-position aldehyde group and a 2-position pinacol-protected boronate ester. The pinacol ester protects the boronic acid from premature protodeboronation and improves the compound's stability and handling characteristics compared to the free boronic acid form.

The aldehyde functionality allows this compound to participate in condensation reactions (e.g., reductive amination, imine formation, Wittig olefination), while the Bpin group enables it to serve as an aryl/heteroaryl boron partner in palladium-catalyzed Suzuki–Miyaura cross-coupling reactions. This dual reactivity makes it a powerful bifunctional linker and building block in medicinal chemistry, materials science, and total synthesis.

Materials and Equipment Required

• 5-Formylfuran-2-boronic acid, pinacol ester (F733265, Aladdin Scientific)
• Appropriate coupling partner (aryl/vinyl halide or pseudohalide for Suzuki coupling)
• Palladium catalyst (e.g., Pd(PPh₃)₄ or Pd(dppf)Cl₂) — for cross-coupling applications
• Base (e.g., K₂CO₃, Cs₂CO₃, or K₃PO₄) — for Suzuki coupling
• Anhydrous solvent (e.g., DMF, dioxane, THF, or toluene)
• Water (co-solvent for Suzuki coupling)
• Inert gas supply (N₂ or Ar) and Schlenk line or glovebox
• Magnetic stir plate and stir bar
• Reflux condenser and round-bottom flask
• Standard analytical equipment (TLC, HPLC, NMR) for monitoring and characterization
• Personal protective equipment (lab coat, gloves, safety glasses)

Step-by-Step Protocol: Suzuki–Miyaura Cross-Coupling

Preparation:

1. Oven-dry all glassware overnight at 120 °C and allow to cool under vacuum or inert atmosphere before use.
2. Degas all solvents by sparging with N₂ or Ar for at least 15 minutes, or by freeze-pump-thaw cycles.
3. Weigh 5-Formylfuran-2-boronic acid, pinacol ester (F733265) and the aryl halide coupling partner in the desired stoichiometric ratio (typically 1.0–1.5 equivalents of the Bpin reagent relative to the halide).

Reaction Setup:

4. Charge the round-bottom flask with the aryl halide, F733265, palladium catalyst (typically 1–5 mol%), and base under inert atmosphere.
5. Add the degassed solvent mixture (e.g., dioxane/water, 4:1 v/v).
6. Seal the flask, purge with inert gas, and heat to the desired temperature (typically 80–100 °C) with stirring.
7. Monitor reaction progress by TLC or analytical HPLC at appropriate intervals.

Workup:

8. Allow the reaction mixture to cool to room temperature upon completion.
9. Dilute with ethyl acetate and wash sequentially with water and brine.
10. Dry the organic layer over anhydrous Na₂SO₄ or MgSO₄, filter, and concentrate under reduced pressure.
11. Purify the crude product by column chromatography or recrystallization as appropriate.
12. Characterize the isolated product by ¹H NMR, ¹³C NMR, and MS.

Note: Reaction conditions (temperature, catalyst loading, base, solvent) should be optimized for each specific substrate pair. The aldehyde group in the product may require protection if it interferes with subsequent transformations.

Storage, Stability, and Safety Considerations

Storage: Store 5-Formylfuran-2-boronic acid, pinacol ester in a cool, dry location away from moisture, light, and incompatible materials (strong oxidizing agents, strong bases). Seal the container tightly and consider storing under an inert atmosphere (N₂ or Ar) after each use to minimize exposure to atmospheric moisture, which can hydrolyze the pinacol ester and liberate the free boronic acid over time.

Stability: The pinacol ester form is substantially more stable than the free boronic acid; however, prolonged exposure to moisture or aqueous conditions can lead to slow hydrolysis of the Bpin group. The aldehyde group is susceptible to oxidation under aerobic conditions. Periodic re-analysis by NMR or TLC is recommended for long-stored material to confirm purity before use.

Safety: Follow standard laboratory safety practices. Wear appropriate PPE including lab coat, chemical-resistant gloves, and safety glasses. Consult the Safety Data Sheet (SDS) for F733265 prior to handling. Avoid inhalation of dust or vapors. Dispose of waste in accordance with local regulations for organoboron chemical waste.