Potassium Phenyltrifluoroborate | CAS 153766-81-5 | ≥97%

Suzuki–Miyaura cross-coupling with enhanced stability — potassium phenyltrifluoroborate is the prototypical member of the organotrifluoroborate salt family developed by Molander and co-workers as air-stable, crystalline surrogates for boronic acids in palladium-catalysed cross-coupling reactions. Unlike boronic acids, which can undergo protodeboronation, oxidative homocoupling, and variable stoichiometry due to anhydride formation, potassium trifluoroborates are monomeric, free-flowing solids with precisely defined molecular weights. This enables accurate stoichiometric control in coupling reactions — a critical advantage in process chemistry and pharmaceutical manufacturing (Molander, G. A.; Ellis, N. Acc. Chem. Res. 2007, 40, 275).

Ligand-free cross-coupling with diazonium salts — potassium phenyltrifluoroborate undergoes ligand-free palladium-catalysed cross-coupling with arenediazonium tetrafluoroborates to give biaryls in good yields. The enhanced nucleophilicity of the trifluoroborate anion compared to the corresponding boronic acid enables these reactions to proceed without the need for phosphine ligands, simplifying reaction setup and reducing catalyst cost. This methodology provides a practical route to unsymmetrical biaryls from readily available aniline-derived diazonium salts.

Rhodium-catalysed 1,2- and 1,4-additions — in the presence of dicarbonyl(acetylacetonato)rhodium(I) as catalyst, potassium phenyltrifluoroborate adds to aldehydes (1,2-addition) to give secondary diarylmethanol products, and to α,β-unsaturated ketones (1,4-conjugate addition) to give saturated ketone products. These rhodium-catalysed additions complement palladium-catalysed cross-coupling and provide access to C–C bonds that are difficult to form by other methods (Batey, R. A.; Thadani, A. N.; Smil, D. V. Org. Lett. 1999, 1, 1683).

Copper-mediated Chan–Lam coupling — potassium phenyltrifluoroborate participates in copper-mediated oxidative coupling with amines, amides, and phenols to form C–N and C–O bonds under mild conditions. The trifluoroborate salt offers improved functional group tolerance and handling compared to boronic acids in these transformations, which are widely used in medicinal chemistry for the late-stage introduction of aryl groups onto heteroatom-containing substrates.

Benchmark and model substrate — as the simplest aryl trifluoroborate salt, potassium phenyltrifluoroborate serves as the standard reference compound for developing and optimising new cross-coupling methodologies. New catalyst systems, ligand designs, solvent combinations, and reaction conditions are routinely validated using this substrate before extension to more complex trifluoroborate partners. Its well-characterised reactivity profile and commercial availability make it an essential tool for methodology development in organometallic chemistry.

Advantages over boronic acids — potassium organotrifluoroborates offer several practical advantages over the corresponding boronic acids: indefinite bench stability without degradation, no anhydride formation, precise stoichiometry, compatibility with aqueous reaction conditions, and tolerance of a wide range of functional groups. These properties have made trifluoroborate salts the preferred boron coupling partners in many industrial and pharmaceutical process chemistry applications where reproducibility and scalability are paramount (Darses, S.; Genet, J.-P. Chem. Rev. 2008, 108, 288).

Electrochemical and photocatalytic applications — potassium phenyltrifluoroborate has been employed as a radical precursor in photoredox-catalysed and electrochemical C–C bond-forming reactions, where single-electron oxidation of the trifluoroborate generates an aryl radical that couples with electron-deficient alkenes and heteroarenes under mild conditions.