5-Hydroxy-1-methyl-1H-pyrazole CAS 33641-15-5 98% Off White Solid Pharmaceutical Building Block Fine Chemical Intermediate

1. Product Overview

5-Hydroxy-1-methyl-1H-pyrazole (CAS 33641-15-5) is a fundamental pyrazole heterocycle with the molecular formula C₄H₆N₂O and a molecular weight of 98.10. Structurally characterized by a methyl group at the N-1 position and a hydroxyl group at the C-5 position, this compound exists predominantly in the tautomeric hydroxy form rather than the oxo form. It typically presents as an off-white to pale yellow solid with a melting point ranging from 110 to 114 °C. As a versatile pharmaceutical building block, it offers two distinct reactive sites: the phenolic hydroxyl group, which can undergo alkylation or acylation, and the aromatic ring, which participates in electrophilic substitution. Supplied at 98% minimum purity, it is a critical intermediate in the synthesis of Active Pharmaceutical Ingredients (APIs), agrochemicals, and specialty fine chemicals.

2. Key Features and Advantages

• High Purity Standard: Minimum 98% assay ensures consistent reaction kinetics and high yields in multi-step pharmaceutical syntheses.

• Versatile Reactivity: The presence of both a hydroxyl group and an N-methyl pyrazole ring allows for diverse chemical transformations, including etherification, esterification, and metal-catalyzed cross-coupling.

• Structural Stability: The methyl group at the nitrogen atom prevents tautomerism issues associated with NH-pyrazoles, providing a stable scaffold for drug design.

• Excellent Handling Properties: Supplied as a free-flowing off-white solid, facilitating precise weighing and minimizing dust generation during laboratory handling.

• Broad Synthetic Utility: Serves as a key precursor for constructing complex heterocyclic systems found in numerous bioactive molecules.

• Regulatory Compliance: Manufactured under strict quality control with full documentation (CoA, MSDS) suitable for regulated markets.

3. Main Applications

• Pharmaceutical Intermediates: A key building block for synthesizing pyrazole-containing drugs. It is notably used in the production of topramezone (a herbicide) and serves as a scaffold for developing anti-inflammatory, antiviral, and anticancer agents.

• Agrochemical Synthesis: Utilized in the manufacture of pesticides and herbicides where the pyrazole moiety contributes to biological activity against specific enzymatic targets in plants or pests.

• Organic Synthesis: Acts as a nucleophile in alkylation reactions to produce ethers and esters, or as a ligand precursor in coordination chemistry for catalysis.

• Dye and Pigment Chemistry: Employed in the synthesis of pyrazolone-based dyes, although its primary market remains in life sciences and crop protection.

• Research & Development: Widely used in medicinal chemistry for library synthesis and structure-activity relationship (SAR) studies involving nitrogen heterocycles.

4. Technical Specifications

5. Storage and Handling

Store in a tightly sealed container in a cool, dry, and well-ventilated area away from direct light. Maintain at room temperature (15-25 °C); for long-term storage, refrigeration (2-8 °C) is recommended to preserve reactivity and prevent discoloration. The compound is hygroscopic; ensure containers are tightly closed after each use to prevent moisture absorption. Handle in a well-ventilated area or fume hood. Wear appropriate personal protective equipment (PPE), including safety goggles, nitrile gloves, and a laboratory coat. Avoid generating dust. Keep away from strong oxidizing agents and strong acids. Wash hands thoroughly after handling. Dispose of waste in accordance with local environmental regulations for organic nitrogen compounds.

6. Safety Overview

This substance may cause mild irritation to the skin, eyes, and respiratory system. Signal Word: Warning. Hazard Statements: H315 - Causes skin irritation; H319 - Causes serious eye irritation; H335 - May cause respiratory irritation. Precautionary Statements: P261 - Avoid breathing dust/fume/mist; P264 - Wash skin thoroughly after handling; P271 - Use only outdoors or in a well-ventilated area; P280 - Wear protective gloves/protective clothing/eye protection/face protection; P302+P352 - IF ON SKIN: Wash with plenty of soap and water; P305+P351+P338 - IF IN EYES: Rinse cautiously with water for several minutes; remove contact lenses if present and easy to do; continue rinsing; P312 - Call a poison center/doctor if you feel unwell; P332+P313 - If skin irritation occurs: Get medical advice/attention; P337+P313 - If eye irritation persists: Get medical advice/attention; P362 - Take off contaminated clothing and wash before reuse; P403+P233 - Store in a well-ventilated place; keep container tightly closed; P501 - Dispose of contents/container in accordance with local/regional/national regulations. In case of contact, rinse affected area with copious water. If ingested, rinse mouth and seek medical attention if symptoms develop. Always refer to the latest Safety Data Sheet (SDS) before use.