4-Carboxyphenylboronic acid | CAS 14047-29-1 | ≥97%

Suzuki–Miyaura cross-coupling — 4-carboxyphenylboronic acid is widely used in palladium-catalysed Suzuki–Miyaura reactions to introduce a carboxylic acid-functionalised aryl group onto halogenated substrates. The resulting biaryl-4-carboxylic acid products serve as intermediates in pharmaceutical synthesis, including the preparation of ultra-potent HIV-1 protease inhibitors based on the amprenavir scaffold, and isoquinolones via regioselective cross-coupling followed by tandem aminocarbonylation and annulation (Sigma-Aldrich, product 456772).

Chan–Lam coupling — 4-carboxyphenylboronic acid participates in copper-catalysed Chan–Lam-type S-arylation with aryl boronic acids at room temperature. This provides a mild, ligand-free route to diaryl thioethers bearing a carboxylic acid handle, enabling further derivatisation of the coupled products without the need for protecting group chemistry.

Glucose-responsive polymers and sensors — the boronic acid moiety reversibly binds diol groups of saccharides, while the carboxylic acid group provides a site for polymer conjugation. This bifunctional reactivity has been exploited in the synthesis of glucose-sensitive boronic acid-bearing block copolymers for potential applications in self-regulated insulin delivery systems and continuous glucose monitoring. The compound has also been used to functionalise poly-silicon nanowires (poly-SiNW) for the electrochemical detection of dopamine via boronate–diol complexation (Alfa Chemistry, CAS 14047-29-1).

Surface functionalisation and latex chemistry — 4-carboxyphenylboronic acid undergoes condensation reactions with stabiliser chains at the surface of polystyrene latex particles, introducing boronic acid recognition elements onto colloidal surfaces. This enables the preparation of saccharide-responsive latex systems for diagnostic assays and affinity separation of glycoproteins.

Metal–organic frameworks (MOFs) — the orthogonal reactivity of the carboxylic acid and boronic acid groups makes 4-carboxyphenylboronic acid a candidate linker for constructing mixed-connectivity metal–organic frameworks. The carboxylate coordinates to metal clusters (Zn, Cu, Zr) while the boronic acid provides additional binding or post-synthetic modification sites, enabling the design of porous materials with tuneable guest recognition properties.

Corrosion inhibition — 4-carboxyphenylboronic acid has been studied as a corrosion inhibitor for carbon steel in CO₂-containing environments. The compound adsorbs onto the steel surface through both the carboxylate and boronate functionalities, forming a protective film that reduces the corrosion rate under conditions relevant to oil and gas pipeline infrastructure (Nam, N. D. et al. Corros. Sci. 2013, 76, 257).

Fluorescence and quantum dot applications — 4-carboxyphenylboronic acid has been used to induce pH sensitivity on the fluorescence lifetime of quantum dots conjugated with near-infrared fluorescent dyes. The pH-dependent equilibrium between trigonal and tetrahedral boron modulates the photophysical properties of the conjugate, providing a ratiometric sensing platform for intracellular pH measurement.

Derivatisation and isotopic labelling — the carboxylic acid group enables conjugation to amines via standard amide coupling, while the boronic acid group provides sites for esterification with diols. This dual reactivity has been exploited for the derivatisation of polyvinylamine and for the synthesis of isotopically labelled organomercury compounds for environmental tracer studies.