Pyrazole-3-boronic Acid Hydrate | CAS 1310383-92-6 | ≥98%

Suzuki–Miyaura cross-coupling — specialist conditions required: Pyrazole-3-boronic acid hydrate is applied in palladium-catalysed Suzuki–Miyaura cross-coupling to introduce the pyrazol-3-yl unit into aryl and heteroaryl halide scaffolds — an important but technically demanding transformation. The unprotected pyrazole NH can partially inhibit palladium catalysis by coordinating to the metal centre, so successful coupling requires specialist conditions: bulky phosphine ligands (SPhos, XPhos) with second-generation Pd precatalysts, elevated temperatures (100 °C), and slightly increased reagent loadings. These conditions are thoroughly optimised in the literature and are reliably reproducible, but should be followed carefully for best results with this substrate class. For researchers seeking more straightforward Suzuki conditions, the corresponding protected form (N-Boc or N-THP protected pyrazole boronate ester) or the potassium trifluoroborate salt are available as alternatives that avoid the NH inhibition issue — however, these require additional protecting group steps. The unprotected boronic acid hydrate remains the most atom-economical and cost-effective option when the specialist coupling protocol is applied correctly. Clapham et al. (Org. Biomol. Chem. 2009, 7, 2155) documented the synthesis and Suzuki–Miyaura coupling of pyrazolylboronic acids and esters.

Kinase inhibitor drug discovery: The pyrazole ring is one of the five most prevalent nitrogen heterocycles in FDA-approved small molecule drugs, and a particularly important scaffold in kinase inhibitor design — where the pyrazole NH forms critical hydrogen bonds with the kinase hinge region or acts as a pharmacophoric anchor in the ATP binding site. Applied in library synthesis campaigns for kinase hinge-binding fragment exploration — the pyrazol-3-yl group is a documented hinge-binding fragment that has been included in parallel Suzuki coupling panels alongside pyridyl, azaindolyl, and quinolinyl boronic acids for systematic kinase selectivity profiling. Its hydrogen bond donor/acceptor combination via the NH and ring nitrogen makes it an unusually versatile fragment for ATP-site engagement across multiple kinase families including JAK, ALK, CSF1R, and MET.

Phenol bioisostere in medicinal chemistry: Widely applied as a bioisostere for the phenol group in drug candidates. The pyrazole NH acts as a hydrogen bond donor similarly to a phenolic OH, while the ring nitrogen at N2 provides an additional hydrogen bond acceptor, giving a combined donor/acceptor profile that can enhance target binding relative to simple phenol. Crucially, the pyrazole ring is not subject to glucuronidation or sulfation — the main Phase II metabolic pathways that rapidly inactivate phenol-containing drugs — providing dramatically improved metabolic stability and longer half-life in vivo. Used in lead optimisation campaigns to replace metabolically labile phenol groups in drug candidates, the pyrazole bioisostere typically improves oral bioavailability, reduces clearance, and extends plasma half-life while maintaining or improving binding affinity. Applied in matched molecular pair (MMP) analyses comparing phenol vs pyrazolyl analogues across kinase, GPCR, and enzyme inhibitor series.

Optics, materials science, and agrochemical building block: Applied in the synthesis of pyrazole-containing fluorescent and luminescent materials for optics applications — pyrazole-aryl conjugates are used as fluorescent chromophores, optical brighteners, and ligands in luminescent metal complexes. The boronic acid provides direct Suzuki coupling access to 3-arylpyrazole frameworks without requiring pre-formed organolithium or Grignard reagents. Also applied as a building block for pyrazole-containing agrochemical active ingredients — the pyrazole ring is a recurring motif in commercial fungicides, insecticides, and herbicides across multiple compound classes, making this boronic acid a relevant intermediate for both agrochemical synthesis and crop protection research programmes.