Chemical Identity and Structure

3-Amino-4-hydroxyphenylboronic acid pinacol ester (Aladdin SKU A732727) is an arylboronic acid ester in which the boron atom is protected as a cyclic pinacol (2,3-dimethyl-2,3-butanediol) ester. The parent phenyl ring carries two additional substituents: a primary amino group (–NH₂) at the 3-position and a phenolic hydroxyl group (–OH) at the 4-position, placed ortho to each other. This arrangement creates an intramolecular hydrogen-bonding interaction between the amine and hydroxyl groups, which influences the compound's stability, solubility, and reactivity profile.

The pinacol boronate ester masking of the boronic acid offers several practical advantages over the free boronic acid form: improved stability toward hydrolysis and protodeboronation during storage, reduced tendency to form anhydrides, and enhanced compatibility with a broader range of reaction conditions. The ester can be readily unmasked to the free boronic acid under mildly acidic aqueous conditions when required.

The simultaneous presence of three orthogonal reactive handles — the boronate ester, the free amine, and the phenol — makes this compound exceptionally useful as a multifunctional building block in complex molecule synthesis.

Key Applications in Chemical Research

Suzuki–Miyaura Cross-Coupling: The pinacol boronate ester is the most widely used boron nucleophile in palladium-catalysed Suzuki–Miyaura reactions. 3-Amino-4-hydroxyphenylboronic acid pinacol ester can be coupled with aryl or vinyl halides and triflates to construct biaryl or styryl frameworks bearing amine and phenol functionality — motifs prevalent in pharmaceuticals, agrochemicals, and functional materials.

Chan–Lam Coupling: The arylboronic acid form (accessed by hydrolysis of the pinacol ester) participates in copper-mediated Chan–Lam N- or O-arylation reactions, allowing introduction of the aminophenol aryl moiety onto nitrogen- or oxygen-containing nucleophiles under mild, often aerobic conditions.

Pharmaceutical and Heterocycle Synthesis: The ortho amine–phenol relationship makes this compound a precursor to benzoxazoles, benzimidazoles, and related five-membered heteroaromatics via condensation with aldehydes or carboxylic acids. These scaffolds appear frequently in drug discovery programs targeting kinases, proteases, and antimicrobial targets.

Bioorthogonal and Fluorescent Probe Construction: The primary amine provides a handle for acylation, reductive amination, or NHS-ester conjugation, enabling attachment of the arylboronic acid motif to peptides, proteins, or fluorophores. Arylboronic acids are well-documented receptors for cis-diols and saccharides, underpinning applications in glucose sensing and lectin-mimetic chemistry.

Material Science: Phenylboronic acid pinacol esters are used as monomers or functional end-groups in the preparation of dynamic covalent polymers and self-healing materials that exploit reversible boronate ester bond formation.

Handling, Storage, and Safety Considerations

Storage: The compound should be stored in a tightly sealed container under an inert atmosphere (nitrogen or argon) in a cool, dry location, away from moisture, heat, and direct light. Boronic acid pinacol esters are susceptible to slow hydrolysis in the presence of atmospheric moisture, so desiccant-protected storage is recommended. Refrigerated storage (2–8 °C) is advisable for long-term preservation of potency.

Handling: Standard laboratory precautions for fine chemical handling apply. Work in a well-ventilated fume hood, use appropriate personal protective equipment (gloves, safety glasses, lab coat), and avoid generating dust. The aromatic amine functionality warrants careful handling; aromatic amines as a class are potentially sensitising agents and should not be inhaled or allowed to contact skin.

Solubility: Arylboronic acid pinacol esters are generally soluble in common organic solvents such as dichloromethane, THF, ethyl acetate, DMF, and DMSO. Solubility in water is limited without co-solvent assistance. For biological assay stock solutions, DMSO is the recommended vehicle.

Stability: Intact pinacol ester is more stable than the free boronic acid. Avoid strongly acidic or basic conditions, oxidants, and prolonged exposure to protic solvents, all of which accelerate ester hydrolysis. The primary amine is susceptible to diazotisation under strongly acidic conditions with nitrous acid; handle accordingly.

Note: Always consult the current Safety Data Sheet (SDS) provided by Aladdin Scientific before use.

Ordering and Availability from Aladdin Scientific

3-Amino-4-hydroxyphenylboronic acid pinacol ester is available from Aladdin Scientific under SKU A732727. Aladdin Scientific offers this compound to research institutions, pharmaceutical companies, and industrial laboratories globally. Inquiries regarding bulk quantities, custom packaging, certificates of analysis, and regulatory documentation (SDS, specification sheets) can be directed to Aladdin Scientific's technical sales team via the company website at aladdin-e.com.

When ordering, researchers should confirm the desired quantity, purity grade, and any specific documentation requirements (e.g., HPLC purity certificate, NMR data) at the time of purchase to ensure uninterrupted research workflows. Aladdin Scientific's catalogue includes a broad portfolio of arylboronic acids and pinacol esters, making it a single-source supplier for multi-step boronate chemistry projects.