4-Borono-2-methylbenzoic acid: Properties & Lab Applications

4-Borono-2-methylbenzoic acid(contains varying amounts of Anhydride) is a bifunctional organoboron building block bearing both a boronic acid group and a carboxylic acid on a methyl-substituted benzene ring, making it a versatile reagent for cross-coupling reactions, medicinal chemistry, and materials science research.

Chemical Name

4-Borono-2-methylbenzoic acid (contains varying amounts of Anhydride)

SKU / Catalog Number

B733246

Functional Groups

Boronic acid (–B(OH)₂) and carboxylic acid (–COOH) on a methylbenzene scaffold

Key Impurity Note

Contains varying amounts of the corresponding boroxine anhydride; purity should be assessed prior to sensitive applications

Primary Applications

Suzuki–Miyaura cross-coupling, bioconjugation, medicinal chemistry building block

Storage Recommendation

Store in a cool, dry place; protect from moisture to minimise anhydride formation

Chemical Identity and Structure

4-Borono-2-methylbenzoic acid is an arylboronic acid in which the benzene ring carries a methyl substituent at the 2-position (ortho to the carboxylic acid) and a boronic acid group at the 4-position (para to the carboxylic acid). The simultaneous presence of the electron-withdrawing carboxylic acid and the Lewis-acidic boronic acid moiety on the same aromatic ring creates a multifunctional scaffold that can participate in diverse chemical transformations.

An important characteristic of this compound is that it contains varying amounts of the corresponding boroxine anhydride—a cyclic trimeric dehydration product formed when boronic acids lose water. This anhydride content is common among arylboronic acids and does not necessarily diminish reactivity, as boroxines are generally considered reactive equivalents of boronic acids in many synthetic protocols. However, researchers should account for this when calculating stoichiometry or characterising purity by techniques such as ¹H NMR or titration.

Research Applications

Suzuki–Miyaura Cross-Coupling: As with most arylboronic acids, 4-Borono-2-methylbenzoic acid serves as an aryl boron partner in palladium-catalysed Suzuki–Miyaura reactions, enabling the formation of biaryl C–C bonds. The carboxylic acid handle offers a convenient site for further derivatisation or for directing the molecule into subsequent amide-coupling or esterification steps.

Medicinal Chemistry and Drug Discovery: Bifunctional boronic acid/carboxylic acid motifs are valuable in fragment-based drug discovery and the construction of protease inhibitors. The boronic acid group is known to interact with active-site serine or threonine residues, while the carboxylate can engage in hydrogen-bonding or salt-bridge interactions with target proteins.

Bioconjugation and Materials Science: Boronic acids form reversible covalent bonds with 1,2- and 1,3-diols, enabling the design of glucose-responsive systems, saccharide sensors, and dynamic covalent materials. The carboxylic acid group provides an orthogonal coupling handle for surface functionalisation or polymer incorporation.

Handling, Storage and Purity Considerations

Anhydride Content: The anhydride present in this material is the boroxine (cyclic boronic anhydride) formed by intermolecular dehydration of three boronic acid molecules. Because boroxines readily rehydrate in the presence of water, the effective boronic acid content can be restored by dissolving the material in aqueous media or by brief exposure to humid air before use. For quantitative work, determine actual boronic acid equivalents by ¹H NMR integration or by argentometric/potentiometric titration.

Moisture Sensitivity: Although boroxine formation is reversible, storing the compound under anhydrous conditions slows interconversion and helps maintain a consistent composition between lots. Recommended storage is in a tightly sealed container in a cool (2–8 °C or room temperature per supplier specification), dry location, away from strong bases and oxidising agents.

Handling Precautions: Standard laboratory personal protective equipment (gloves, lab coat, safety glasses) should be worn. Consult the Safety Data Sheet (SDS) for full hazard information before use. Boronic acids are generally of low acute toxicity, but fine dust should not be inhaled.

Ordering Information

4-Borono-2-methylbenzoic acid (contains varying amounts of Anhydride) is available from Aladdin Scientific under catalog number B733246. Contact your local Aladdin representative or visit the product page for current pricing, available pack sizes, and certificate of analysis (CoA) documentation. Bulk quantities may be available upon request.

Frequently asked questions

Why does this boronic acid contain varying amounts of anhydride, and does it affect reactivity?

Boronic acids spontaneously undergo intermolecular dehydration to form cyclic trimeric boroxine anhydrides, especially under dry or warm storage conditions. This process is reversible—boroxines readily rehydrate in aqueous or protic media. In most synthetic applications, including Suzuki–Miyaura coupling, boroxines are reactive equivalents of the parent boronic acid, so reactivity is generally not significantly compromised. For stoichiometrically precise work, determine the actual boronic acid content by NMR or titration.

What are the recommended storage conditions for B733246?

Store 4-Borono-2-methylbenzoic acid in a tightly sealed container in a cool, dry location to minimise moisture-driven interconversion between the boronic acid and boroxine forms. Keep away from strong bases, oxidising agents, and prolonged exposure to humid air. Refer to the product's Certificate of Analysis or SDS for lot-specific storage temperature recommendations.

How can I use 4-Borono-2-methylbenzoic acid as a building block in synthesis?

This compound offers two independent reactive handles: the boronic acid group for Suzuki–Miyaura cross-coupling or diol-binding chemistry, and the carboxylic acid group for amide bond formation, esterification, or surface immobilisation. Researchers can exploit these orthogonal functionalities sequentially to construct complex bifunctional molecules, pharmaceutical intermediates, or functional materials. Standard coupling conditions apply for each transformation; consult relevant literature for optimised protocols.

Is the anhydride content declared on the Certificate of Analysis?

Purity specifications and analytical data are provided on the lot-specific Certificate of Analysis (CoA) available from Aladdin Scientific. If the anhydride proportion is critical for your application, request the CoA for your specific lot or perform in-house quantification by ¹H NMR before use.

References

1. Hall, D. G. (Ed.) Boronic Acids: Preparation and Applications in Organic Synthesis, Medicine and Materials. Wiley-VCH, 2011.
2. Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chemical Reviews, 1995, 95(7), 2457–2483. doi:10.1021/cr00039a007
3. Springsteen, G.; Wang, B. A detailed examination of boronic acid–diol complexation. Tetrahedron, 2002, 58(26), 5291–5300. doi:10.1016/S0040-4020(02)00489-1

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