4-Biphenylboronic Acid | CAS 5122-94-1 | ≥98%

Suzuki–Miyaura cross-coupling for terphenyl and oligoaryl synthesis — 4-biphenylboronic acid is a building block for palladium-catalysed Suzuki–Miyaura reactions, coupling with aryl and heteroaryl halides to form p-terphenyl and higher oligoaryl frameworks. Because the boronic acid already carries a preformed biphenyl unit, a single cross-coupling step extends the conjugated system by two aromatic rings, providing efficient access to linear oligophenylenes. These extended π-systems are of central importance in organic electronics, liquid crystal chemistry, and materials science (Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457).

Liquid crystal intermediates — 4-biphenylboronic acid is used in the synthesis of rod-shaped mesogens for liquid crystal displays. Suzuki coupling with halogenated arenes bearing terminal alkyl or alkoxy chains generates 4,4’’-disubstituted terphenyls, a core structural motif in nematic and smectic liquid crystal materials. The high linearity and rigidity of the terphenyl axis, combined with tuneable peripheral substituents, makes this boronic acid a preferred starting material for liquid crystal research and development (ChemicalBook, CAS 5122-94-1).

Conjugated oligomer and polymer synthesis — 4-biphenylboronic acid serves as a monomer or end-capping reagent in the synthesis of conjugated oligomers and polymers for organic light-emitting diodes (OLEDs), organic photovoltaics (OPVs), and organic field-effect transistors (OFETs). Suzuki polycondensation of diboronic acids with dihalides is one of the principal routes to poly(para-phenylene) and related conjugated polymers, and 4-biphenylboronic acid provides a bifunctional extension unit compatible with this methodology.

Thienyl–phenylene hybrid materials — ChemicalBook documents the use of 4-biphenylboronic acid in the Suzuki coupling with 2-(4-bromophenyl)thiophene and 2,5-diiodothiophene to prepare thienyl-substituted terphenyls and quinquephenyls. These thiophene–phenylene hybrid oligomers are investigated as organic semiconductors with tuneable HOMO–LUMO gaps and charge transport properties for thin-film transistor applications.

Chemiluminescence enhancement — 4-biphenylboronic acid has been identified as an effective enhancer of horseradish peroxidase (HRP)-catalysed chemiluminescent oxidation of luminol and pyridopyridazine derivatives. In comparative studies, 4-biphenylboronic acid produced enhancement comparable to 4-iodophenylboronic acid and demonstrated synergistic enhancement when combined with 4-iodophenol, increasing light emission intensity by 25% beyond the sum of individual effects. This property makes it useful in the development of ultrasensitive immunoassays and biosensor systems (Nozaki, O.; Ji, X.; Kricka, L. J. J. Biolumin. Chemilumin. 1995, 10, 151).

Saccharide recognition by capillary electrophoresis — 4-biphenylboronic acid forms reversible covalent complexes with diol groups of mono- and disaccharides, enabling molecular recognition and separation of sugars by capillary electrophoresis with chemiluminescence detection. Apparent stability constants between the boronic acid and saccharides including 1-methyl-D-glucoside, D-sucrose, and D-fructose have been determined using this system.