5-Pyrimidylboronic Acid | CAS 109299-78-7 | ≥98%

5-Pyrimidylboronic Acid (pyrimidin-5-ylboronic acid) is a compact N-rich heteroarylboronic acid for installing the pyrimidin-5-yl unit into biaryl and heteroaryl frameworks.

May contain small amounts of the cyclic anhydride 5-pyrimidylboroxine. Under aqueous or basic coupling conditions the two forms re-equilibrate and the impact on yield is minor.

Applications and Reactions

• Suzuki–Miyaura cross-coupling: couples with aryl, heteroaryl, or alkenyl electrophiles to give pyrimidin-5-yl biaryls, heterobiaryls, and styrenyl heteroarenes.
• Heteroaryl–heteroaryl construction: documented in the synthesis of heteroarylpyrimidines by coupling with heteroaryl halide partners.
• Protodeboronation-sensitive coupling partner: N-heteroarylboronic acids can show condition-dependent protodeboronation; masked boronate forms or milder coupling conditions may improve reliability where instability is observed.
• Pyrimidin-5-yl scaffold installation: introduces a diazine ring with two ring nitrogens, useful when replacing phenyl or pyridyl units in structure–property studies.
• Pharmaceutical and agrochemical intermediate: provides direct access to N-rich heteroaryl fragments for medicinal-chemistry and agrochemical intermediate libraries.
• Protected boronate derivatives: precursor to pinacol, neopentyl glycol, and other boronate forms where improved handling or staged cross-coupling is preferred.

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.