What Is 1-(Tetrahydropyran-2-yl)-1H-pyrazole-5-boronic Acid Pinacol Ester CAS 903550-26-5?

1-(Tetrahydropyran-2-yl)-1H-pyrazole-5-boronic acid pinacol ester is a protected pyrazole boronic ester used primarily as a research and pharmaceutical-intermediate building block. Its CAS number is 903550-26-5, and its structure combines a pyrazole ring, a tetrahydropyranyl protecting group, and a pinacol boronate functional group. Based on the stated structure, the corresponding molecular formula is commonly represented as C₁₄H₂₄BN₂O₃, with an approximate molecular weight of 279.16 g/mol. I recommend confirming the formula, assay, appearance, and storage conditions against the current supplier specification or certificate of analysis before using the material in a regulated or scale-up process.

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Identity and Chemical Structure

This compound contains one pyrazole ring with two nitrogen atoms and a boronic acid pinacol ester at the 5-position. The pyrazole nitrogen is substituted with a tetrahydropyran-2-yl group, which can function as a protecting group during multistep synthetic work. The boronic ester is chemically useful because it can participate in palladium-catalyzed cross-coupling reactions after suitable reaction optimization.

The pinacol ester form is not the same material as the corresponding free boronic acid. Esterification can improve handling and provide a more convenient form for weighing, storage, and synthetic screening, although stability still depends on moisture, temperature, solvent, and packaging. The exact behavior should be evaluated using the supplier’s analytical data rather than inferred only from the name.

The formula and molecular-weight values above are structure-based reference values and should not replace a manufacturer’s release documentation. For chemical nomenclature and structure interpretation, I use internationally recognized chemical terminology and recommend checking the current record in a trusted chemical database or the supplier’s technical file. The IUPAC Gold Book provides authoritative terminology for functional groups and chemical concepts, while a current SDS remains the controlling document for handling and hazard information.

Core Functions in Synthetic Chemistry

Building Block for Carbon–Carbon Bond Formation

The boronic ester group is the most synthetically distinctive feature of this molecule. In suitable reaction systems, it may serve as a partner in Suzuki–Miyaura-type cross-coupling with an appropriate aryl, heteroaryl, or vinyl halide. The reaction outcome depends on the catalyst, base, solvent, water content, temperature, substrate compatibility, and purification method, so I describe this compound as a potential coupling intermediate rather than a guaranteed-performing reagent.

Its boronate group contains one boron atom and two ester oxygen atoms within the pinacol-derived portion. This protected form is often selected when a project requires a manageable boronic ester intermediate instead of the free boronic acid. Researchers should confirm hydrolytic stability and coupling performance at laboratory scale before committing to larger quantities.

Temporary Protection of the Pyrazole Nitrogen

The tetrahydropyran-2-yl substituent can protect the pyrazole nitrogen during downstream transformations. Protection may help control regioselectivity or reduce unwanted reactions involving the N–H site, but deprotection conditions must be compatible with the rest of the molecule. Acid sensitivity, reaction time, solvent selection, and temperature can all influence the result.

Because protecting-group removal is substrate-dependent, I recommend screening a small number of conditions rather than assuming that one standard protocol will apply to every route. The appropriate process should be selected using reaction monitoring and impurity analysis. This is especially important when the intermediate is intended for a pharmaceutical development program.

Potential Applications

Pharmaceutical and Medicinal Chemistry Research

This compound may be used in medicinal chemistry as a modular intermediate for preparing substituted pyrazole-containing compounds. Its value comes from combining a protected nitrogen site with a boronic ester handle in one molecule. That combination can support route exploration, analog generation, and late-stage structural diversification.

It is important to distinguish a research intermediate from an active pharmaceutical ingredient. CAS 903550-26-5 should not be described as an approved drug, finished pharmaceutical product, or therapeutic ingredient unless a separate regulatory record supports that claim. Any use in drug development requires route-specific impurity control, analytical characterization, and compliance with the applicable quality system.

Process Development and Custom Synthesis

Process chemists may evaluate this intermediate when developing a sequence that requires selective pyrazole protection and subsequent carbon–carbon bond formation. The material can also be considered for small-scale reaction screening, reference-standard preparation, or custom synthesis planning. Actual suitability depends on the target structure and the availability of compatible reaction conditions.

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For scale-up, I would review not only assay but also water content, residual solvents, particle form, packaging, and lot-to-lot consistency. These factors can affect weighing accuracy, reaction reproducibility, and downstream purification. A small laboratory sample is usually the most reliable starting point when the route has not previously been demonstrated with the selected supplier’s material.

Key Specifications Buyers Should Request

A commercial inquiry should request a current technical data sheet and certificate of analysis. At minimum, I suggest asking for identity confirmation, assay or chromatographic purity, water content where relevant, residual solvents, appearance, and recommended storage conditions. If the compound is intended for a regulated project, the buyer should also clarify the analytical methods and acceptance criteria used for release.

There is no responsible universal storage temperature for every batch unless the manufacturer has established and documented it. Some boronic ester products may be recommended for cool, dry storage, but I advise buyers to follow the product-specific SDS and label rather than applying a generic temperature such as 2–8 °C. The U.S. Occupational Safety and Health Administration Hazard Communication Standard, 29 CFR 1910.1200, emphasizes the importance of accessible hazard communication and safety data for chemical handling.

Handling and Safety Considerations

I recommend treating this compound as a laboratory or industrial chemical intermediate and handling it only under an appropriate institutional safety program. Operators should review the current SDS before opening the package, use suitable protective equipment, avoid generating dust, and work with adequate ventilation or containment. The SDS should determine the required controls because hazard classifications can vary with the substance, impurity profile, and jurisdiction.

Moisture exposure should be minimized when the supplier identifies the boronic ester as moisture-sensitive or provides a dry-storage requirement. Containers should remain closed when not in use, and material should be weighed using procedures that prevent cross-contamination. Spill response, waste disposal, and incompatibility information should be taken directly from the current SDS and site-specific procedures.

For safety data interpretation, I recommend consulting the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (GHS) and the applicable local regulations. These sources provide a framework for hazard communication, but they do not replace the product-specific SDS. I do not recommend assigning a hazard class or transport classification without verified documentation.

How to Evaluate a Supplier

Technical Documentation

A suitable supplier should be able to discuss the product identity, analytical methods, typical package sizes, lead time, and storage guidance. Buyers should ask whether the quoted material is a standard catalog product, a batch-made product, or a custom-manufactured intermediate. This distinction can affect documentation, minimum order quantity, production scheduling, and change-control expectations.

Supply and Quality Communication

Supplier evaluation should include more than the lowest price per gram. I recommend comparing the clarity of the CoA, responsiveness to technical questions, packaging suitability, shipping conditions, and ability to support repeat orders. For pharmaceutical-intermediate projects, it is also useful to clarify whether specifications can be agreed before production and whether samples are available for route verification.

Maison Chemical can support an initial review of the requested CAS number, target quantity, packaging needs, and documentation requirements. We can discuss available supply options for research and pharmaceutical-intermediate applications, subject to batch availability and technical confirmation. Before quotation or purchase, I recommend providing the intended quantity, destination country, required delivery schedule, and any minimum purity or analytical requirements.

Buyer Selection Checklist

• Confirm the CAS number: 903550-26-5.
• Verify the molecular formula and approximate molecular weight against the current supplier record.
• Request a recent certificate of analysis and product-specific SDS.
• Clarify purity, assay method, water content, residual solvents, and appearance.
• Ask about packaging, storage temperature, shelf-life guidance, and transport conditions.
• Confirm sample availability before placing a larger order for a new synthetic route.
• Discuss MOQ, lead time, repeat-batch consistency, and change-notification expectations.

Summary and Next Steps

1-(Tetrahydropyran-2-yl)-1H-pyrazole-5-boronic acid pinacol ester CAS 903550-26-5 is a protected pyrazole boronic ester with potential value in medicinal chemistry, pharmaceutical-intermediate synthesis, and research-scale cross-coupling development. Its key structural features are a tetrahydropyranyl-protected pyrazole nitrogen and a pinacol boronate group, with a structure-based molecular weight of approximately 279.16 g/mol. The compound should be evaluated as a synthetic intermediate, not as an approved pharmaceutical ingredient.

My recommended next step is to compare supplier documentation before comparing price alone. Request the current CoA, SDS, analytical method summary, package options, MOQ, and lead time, then confirm the material in a small-scale reaction if the route is new. For a quotation or technical discussion, contact Maison Chemical with your required quantity, purity target, delivery location, and documentation expectations so we can assess the most appropriate supply option.

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