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

Suzuki–Miyaura cross-coupling: 1-Methyl-1H-pyrazole-4-boronic acid is a widely used heteroaryl boronic acid for palladium-catalysed Suzuki–Miyaura cross-coupling reactions, enabling the formation of carbon–carbon bonds between the 1-methylpyrazol-4-yl group and a broad range of aryl, heteroaryl, and vinyl halides or pseudohalides. The reaction proceeds under standard Suzuki conditions with palladium catalysts such as Pd(dppf)Cl₂ or Pd(PPh₃)₄ in the presence of an aqueous base. A key synthetic advantage of this compound over unprotected pyrazole boronic acids is that the N-methyl group eliminates the acidic NH proton. In unprotected azole boronic acids, the free NH can coordinate to the palladium centre, suppressing catalytic turnover and promoting protodeboronation. With the nitrogen capped as N-methyl, standard catalyst loadings and mild conditions are sufficient, without requiring the specialised bulky phosphine ligands and elevated temperatures that unprotected pyrazole boronic acids demand. The compound is also compatible with microwave-assisted Suzuki protocols, which significantly reduce reaction times while maintaining high yields across electron-rich, electron-poor, and sterically demanding coupling partners.

Kinase inhibitor synthesis and medicinal chemistry: The pyrazole ring is one of the most pharmacologically important five-membered heterocycles in modern drug discovery, present in multiple FDA-approved protein kinase inhibitors across oncology, haematology, and inflammatory disease therapeutic areas targeting kinases including ALK, c-Met, JAK1/2, FGFR, B-Raf, and BTK. 1-Methyl-1H-pyrazole-4-boronic acid provides direct Suzuki-mediated access to the 1-methylpyrazol-4-yl pharmacophore present in many of these structural classes. The 1-methylpyrazol-4-yl motif has been specifically highlighted in c-Met kinase inhibitor programmes, where it provides favourable coplanarity with the drug's core scaffold and makes productive hydrogen-bond contacts with the hinge region of the kinase active site. This boronic acid has also been employed in the synthesis of Aurora-A kinase inhibitors, where a pyrazol-4-yl group is introduced at the C-7 position of an imidazo[4,5-b]pyridine scaffold via Suzuki coupling with chloronitropyridine intermediates.

Agrochemical synthesis: The pyrazole ring is a recurring structural motif in commercial fungicides and herbicides. 1-Methyl-1H-pyrazole-4-boronic acid serves as a building block for introducing the 1-methylpyrazol-4-yl group into agrochemical scaffolds via cross-coupling, providing access to analogues with modified biological activity, improved environmental profiles, or enhanced metabolic stability in plant systems. The ability to rapidly generate libraries of 4-substituted 1-methylpyrazole derivatives from this single boronic acid building block makes it particularly valuable in agrochemical lead optimisation campaigns.

Heterocyclic building block chemistry: Beyond Suzuki coupling, 1-methyl-1H-pyrazole-4-boronic acid can be converted to the corresponding pinacol ester (CAS 761446-44-0) or to the bench-stable lithium hydroxy ate complex — both of which offer improved handling stability and extended shelf life for long-term storage. The lithium ate complex can be employed directly in Suzuki couplings without the need for added base, simplifying reaction setup. The boronic acid itself also participates in Chan–Lam coupling reactions — copper-mediated C–N and C–O bond-forming reactions that allow the attachment of amines, amides, or phenols to the pyrazole ring under mild, base-free conditions.

Materials science and fluorescent frameworks: N-Methylpyrazole-containing building blocks are used in the construction of fluorescent and luminescent materials, where the nitrogen-rich heterocycle contributes to the electronic structure of the emissive framework. 1-Methyl-1H-pyrazole-4-boronic acid enables Suzuki-mediated incorporation of the pyrazole unit into extended conjugated architectures designed for optical applications, including fluorescent sensors, organic light-emitting materials, and coordination polymers. In coordination chemistry, 4-aryl-1-methylpyrazole derivatives prepared from this boronic acid serve as ligands for transition-metal and lanthanide complexes, where the pyrazole nitrogen atoms provide directional coordination sites.