Pyridin-3-ylboronic Acid | CAS 1692-25-7 | ≥95%

Pyridin-3-ylboronic acid (3-pyridineboronic acid, 3-pyridylboronic acid, pyridine-3-boronic acid) is an electron-deficient heteroaryl boronic acid with boron at the pyridine 3-position, two bonds from the ring nitrogen.

It is frequently isolated and supplied partly as the cyclic anhydride tris(3-pyridyl)boroxine. Under aqueous or basic coupling conditions the two forms re-equilibrate and the impact on yield is minor.

Stability and coupling behaviour: Whilst the 2-pyridyl isomer the ring nitrogen sits adjacent to boron and drives rapid protodeboronation (the "2-pyridyl problem"). In the 3-pyridyl isomer, the C-3 the nitrogen is two bonds removed, so the acid is robust and couples directly under standard Pd(PPh₃)₄ or Pd(dppf)Cl₂ / K₂CO₃ conditions, without MIDA or trifluoroborate masking. As with other N-heteroaryls, the Lewis-basic nitrogen can coordinate palladium and slow turnover — including transmetalation and reductive elimination — so bulky electron-rich biarylphosphines are the standard remedy on demanding substrates.

Applications and Reactions

• Suzuki–Miyaura cross-coupling: One of the most widely used pyridylboronic acids; installs the 3-pyridyl group onto aryl, heteroaryl, and vinyl halides — e.g. with halogenated quinolines to give 3-(pyridin-3-yl)quinolines and related heterobiaryls. Phosphine-free palladium protocols are also documented.
• Tandem coupling–annulation: Combines regioselective Suzuki–Miyaura coupling with palladium-catalysed intramolecular aminocarbonylation and annulation to assemble fused nitrogen heterocycles in one sequence.
• Copper-mediated functionalisation: Undergoes copper(II) acetylacetonate–catalysed N-arylation (Chan–Lam-type C–N bond formation) and copper-mediated cyanation, including regioselective cyanation of electron-rich arenes.
• Pharmaceutical building block: Supplies the 3-pyridyl unit of Bcr–Abl tyrosine-kinase inhibitors such as nilotinib (chronic myeloid leukaemia), installed by Suzuki coupling.
• Medicinal-chemistry motif: The 3-pyridyl group is among the most common nitrogen heterocycles in approved drugs and a frequent phenyl bioisostere: replacing phenyl raises aqueous solubility, adds a hydrogen-bond acceptor, and tempers lipophilicity.
• Functional and supramolecular polymers: Prepares linear poly(phenylpyridyl) chains by iterative Suzuki coupling and oligopyridyl foldamers that mimic the α-helix twist.
• Coordination chemistry and framework materials: The pyridyl nitrogen of the products is an N-donor site — a ligand in coordination complexes, a linker in metal–organic frameworks, and the metal-binding element in sensor materials.
• Agrochemical and materials intermediates: Provides cross-coupling access to 3-pyridyl analogue libraries and electron-deficient arylpyridine intermediates for agrochemical and organic-electronics research.

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.