1-Methyl-1H-pyrazole-4-boronic Acid | CAS 847818-55-7 | ≥95%

1-Methyl-1H-pyrazole-4-boronic Acid ((1-methyl-1H-pyrazol-4-yl)boronic acid) is an N-methylated pyrazol-4-yl boronic acid building block.

May contain small amounts of the cyclic anhydride 1-methyl-1H-pyrazol-4-ylboroxine. 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: installs the 1-methylpyrazol-4-yl group onto aryl, heteroaryl, and vinyl electrophiles.
• Protodeboronation profile: boron at C4 (not adjacent to a ring nitrogen) makes it markedly more robust than 2-pyridyl, 5-thiazolyl, or 5-pyrazolyl boronic acids, which protodeboronate within seconds — not inert, though: a pH-dependent rate means couple under matched conditions and store cold.
• N-methyl medicinal-chemistry handle: N-methylation locks the tautomer, caps the donor N–H, and — via the electron-donating methyl — tunes the ring's basicity and electron density; the defined, weakly basic pyridine-type N2 serves as an H-bond acceptor for molecular recognition and ADME tuning.
• Lithium hydroxy ate complex: an isolable, bench-stable form that couples directly in Suzuki reactions without added base.
• Pharmaceutical and agrochemical building block: the pyrazole ring is prominent in both fields; this reagent installs the 1-methylpyrazol-4-yl unit for analogue series.

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.