Potassium Phenyltrifluoroborate

Technical Specifications

Product Description & Scientific Applications

Potassium phenyltrifluoroborate (PhBF₃K) is the potassium salt of the phenyltrifluoroborate anion, an air- and moisture-stable organoboron reagent that transfers a phenyl group in carbon–carbon, carbon–oxygen and carbon–nitrogen bond formation.

Common Scientific Applications

Suzuki–Miyaura cross-coupling. PhBF₃K is the phenylating partner in palladium-catalysed Suzuki–Miyaura coupling across a wide range of electrophiles: benzylic chlorides, giving diarylmethanes in water; dihalogenated heteroarenes, arylating an isothiazole regiospecifically; aryl sulfamates, coupling at a carbon–oxygen bond; and 2-bromoglycals, furnishing 2-C-aryl branched carbohydrates. The coupling tolerates sensitive functionality: an azide on a bromoconduritol survives the reaction and is carried into a subsequent click cycloaddition.

Hydrolytic slow release. In palladium coupling the trifluoroborate does not itself transfer the phenyl group to the metal; it hydrolyses to phenylboronic acid under the reaction conditions, and that boronic acid is the active partner. Matching this release to the rate of catalytic turnover keeps the boronic acid from accumulating, suppressing oxidative homocoupling and protodeboronation.

Rhodium-catalysed conjugate addition. Under rhodium catalysis PhBF₃K adds the phenyl group to the β-position of α,β-unsaturated ketones; with chiral ligands the conjugate addition to cyclohexenone gives 3-phenylcyclohexanone in high enantioselectivity.

Copper-catalysed amination. Copper catalysis couples aryltrifluoroborates with nitrogen nucleophiles: Chan–Lam-type N-arylation joins them to amines, and reaction with aqueous ammonia delivers primary arylamines.

Oxidative hydroxylation. Treatment with hydrogen peroxide and a citric-acid catalyst in water converts PhBF₃K to phenol.

Copper-catalysed carboesterification. PhBF₃K is among the trifluoroborates that act as the carbon source in a copper-catalysed three-component addition of dienes and carboxylic acids, giving allylic esters.

Lewis-acid arylation of acetals. Under boron trifluoride activation, aryltrifluoroborates add to acetal-derived oxocarbenium ions, replacing one alkoxy group with the aryl group to give substituted ethers.

Further applications. The phenyltrifluoroborate anion serves as a weakly coordinating counterion in functional salts, including photoresponsive spin-crossover iron(III) complexes and fluorescent imidazolium salts.

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