3-Cyanophenylboronic Acid | CAS 150255-96-2 | ≥98%

3-Cyanophenylboronic Acid (3-cyanobenzeneboronic acid, m-cyanophenylboronic acid, 3-boronobenzonitrile) is an electron-poor arylboronic acid. The meta-cyano group is strongly electron-withdrawing (Hammett σm ≈ +0.56), lowering the boronic-acid pKa to an estimated value near 7.6 against the parent phenylboronic-acid pKa of 8.76.

The product may contain small amounts of the cyclic anhydride 3-cyanophenylboroxine; under aqueous or basic coupling conditions the two forms re-equilibrate and the impact on yield is minor.

Applications and Reactions

• Suzuki–Miyaura coupling: couples with aryl and heteroaryl halides under matched Pd/phosphine/base conditions to give 3-cyanobiaryl and 3-cyanoaryl–heteroaryl products. The nitrile substituent is generally compatible with Suzuki conditions and remains intact on the coupled scaffold.
• Cyano group as a latent functional handle: after coupling, the meta-CN group on the biaryl product can be converted to tetrazoles (NaN3 / Zn salts under Sharpless–Demko conditions), to carboxylic acids by hydrolysis, to arylmethylamines by catalytic reduction, or to amidoximes and 1,2,4-oxadiazoles via hydroxylamine-derived intermediates. This makes the reagent useful where a compact polar group is needed during coupling but a different functionality is desired later in the sequence.
• Phenylimidazole-based Ir(III) complexes for blue PhOLED research: 3-cyanophenylboronic acid is used to prepare cyanoaryl-substituted phenylimidazole ligands for cyclometalated Ir(III) complexes. The electron-withdrawing cyanoaryl substituent modifies the electronic structure and emission behaviour of the resulting complexes, supporting their use in phosphorescent blue OLED materials research.
• Biaryl phenylalanine amino-acid analogues: Suzuki coupling with halogenated phenylalanine derivatives, in solution or on solid support, gives meta-cyanoaryl-substituted biaryl phenylalanines that retain the nitrile for later polar-group diversification on the coupled framework.
• 4-Aryl-1,8-naphthyridin-2(1H)-one synthesis: Suzuki coupling with 4-halo-1,8-naphthyridin-2(1H)-one precursors gives 4-(meta-cyanoaryl)-1,8-naphthyridin-2(1H)-ones for heterocyclic scaffold synthesis.

Further Reading

For boronic acids, boronic esters, protodeboronation, boroxine content, and Suzuki–Miyaura reagent selection, see NorrChemica's Lab Journal guide: Choosing Your Boron Source for Suzuki–Miyaura Coupling.