2-Fluorophenylboronic Acid | CAS 1993-03-9 | ≥98%

Suzuki–Miyaura cross-coupling: 2-Fluorophenylboronic acid is one of the most widely used ortho-substituted aryl boronic acids in palladium-catalysed Suzuki–Miyaura cross-coupling reactions, enabling efficient construction of 2-fluorobiphenyl scaffolds — structural motifs found extensively in pharmaceuticals, agrochemicals, and liquid crystalline materials. The fluorine atom at the ortho position accelerates the transmetalation step by withdrawing electron density from the boron centre, making this boronic acid a faster coupling partner than unsubstituted phenylboronic acid. However, the ortho-fluorine also increases susceptibility to protodeboronation. For optimal yields, reactions benefit from short reaction times, mild bases (K₂CO₃ or KF rather than strong hydroxide bases), and efficient palladium catalyst systems. Specialised precatalysts bearing bulky biarylphosphine ligands such as SPhos and RuPhos enable room-temperature or low-temperature coupling of ortho-fluorinated boronic acids with aryl chlorides, bromides, and triflates in excellent yields. The ortho-fluorine imposes minimal steric hindrance relative to larger ortho-substituents, making this compound compatible with sterically demanding electrophilic coupling partners including di-ortho-substituted aryl halides.

Rhodium-catalysed enantioselective addition: 2-Fluorophenylboronic acid is employed as an aryl donor in rhodium-catalysed asymmetric 1,4-conjugate addition reactions to α,β-unsaturated carbonyl compounds — including enones, enals, and unsaturated esters. The boronic acid transfers the 2-fluorophenyl group enantioselectively to the β-position of the Michael acceptor, generating chiral products with high enantiomeric excess when used with chiral bisphosphine or diene ligands bound to rhodium. This reaction class is a key tool in asymmetric synthesis for the construction of stereocentres bearing fluorinated aryl groups — motifs of high value in medicinal chemistry because the ortho-fluorine can modulate metabolic stability, lipophilicity, and conformational preference. Beyond conjugate addition, the compound participates in rhodium- and palladium-catalysed substitution reactions on allylic substrates, providing access to branched allylic products bearing the 2-fluorophenyl group with high regio- and enantioselectivity.

Pharmaceutical impurity reference and medicinal chemistry: 2-Fluorophenylboronic acid is a documented impurity reference standard in the manufacture of potassium-competitive acid blocker (P-CAB) pharmaceuticals used for the treatment of gastric acid-related disorders. It is required by pharmaceutical QC laboratories for regulatory analytical methods including impurity profiling and forced degradation studies. More broadly, the 2-fluorophenyl group is one of the most frequently encountered fluorinated aryl motifs in medicinal chemistry. The ortho-fluorine can block metabolically vulnerable positions on the aromatic ring, reduce CYP-mediated oxidation, and modulate pKₐ of adjacent functional groups — making 2-fluorophenylboronic acid a valuable building block for the rapid assembly of fluorinated drug candidates and SAR libraries via Suzuki coupling.

Arylboron difluoride (ArBF₂) Lewis acids and luminescent materials: 2-Fluorophenylboronic acid is used in the preparation of arylboron difluoride (ArBF₂) species — strong Lewis acids formed by treating aryl boronic acids with fluoride sources such as KHF₂ or BF₃·OEt₂. These ArBF₂ compounds serve as Lewis acid catalysts in organic transformations and as fluorescent building blocks in the development of boron-containing luminescent materials, organic light-emitting frameworks, and molecular sensors. The presence of fluorine at both the boron centre (as BF₂) and on the aromatic ring creates a highly electron-deficient system with distinctive photophysical properties — including tuneable absorption and emission wavelengths — that are exploited in the design of fluorescent probes for biological imaging and environmental sensing applications.

Diol recognition, anion receptors, and materials science: Like all aryl boronic acids, 2-fluorophenylboronic acid forms reversible covalent boronate esters with 1,2- and 1,3-diols under mild conditions — a property exploited in saccharide sensors, glucose-responsive materials, and chromatographic separation of diol-containing analytes. The electron-withdrawing ortho-fluorine lowers the pKₐ of the boronic acid, enhancing diol binding affinity at physiological pH relative to unsubstituted phenylboronic acid. The compound has been specifically used in the preparation of phenylboronic catechol esters investigated as anion receptors for polymer electrolyte membranes — materials relevant to fuel cell and battery technology. Fluorinated biphenyl products derived from Suzuki coupling of this boronic acid are also of interest in liquid crystal display (LCD) technology, where fluorinated biphenyls and terphenyls serve as components in nematic liquid crystalline mixtures with tailored dielectric properties and wide operating temperature ranges.