This compound belongs to the class of organic compounds known as pyrazoles. These are compounds containing a pyrazole ring, which is a five-member aromatic ring with two nitrogen atoms (at positions 1 and 2) and three carbon atoms.
External Descriptors
Not available
1. Djoumbou Feunang Y, Eisner R, Knox C, Chepelev L, Hastings J, Owen G, Fahy E, Steinbeck C, Subramanian S, Bolton E, Greiner R, and Wishart DS. ClassyFire: Automated Chemical Classification With A Comprehensive, Computable Taxonomy. Journal of Cheminformatics, 2016, 8:61.
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Application Protocols
No vendor-validated biological assay protocols are provided for this item. Typical laboratory uses involve standard organic synthesis procedures such as CuAAC, Sonogashira coupling, Glaser coupling, or nucleophilic additions after acetylide formation.
General guidance (non-item-specific)
For CuAAC: Combine azide (1.0 equiv), this alkyne (1.0–1.5 equiv), CuSO4 (1–10 mol%), sodium ascorbate (2–20 mol%), and tBuOH/H2O (1:1). Stir at rt until TLC/LC-MS indicates completion; extract and purify.
For Sonogashira: Charge aryl/vinyl halide (1.0 equiv), this alkyne (1.2–1.5 equiv), Pd catalyst (1–3 mol%), CuI (5–10 mol%), base (2–3 equiv), and solvent. Stir under N2 at 40–80°C until complete; work up and purify.
Refer to peer-reviewed literature and adapt conditions to your substrate set. Always consult the item’s CoA and SDS before use.
Biological Roles
This product is a synthetic heteroaromatic small molecule intended for research and chemical synthesis. No endogenous biological role is assigned.
General literature context (no medical claims)
Pyrazole rings are common motifs in bioactive molecules and ligands due to their hydrogen-bonding capacity and tunable basicity. N1-methylation modulates pKa and lipophilicity relative to unsubstituted pyrazoles.
Terminal alkynes are frequently used as “click handles” to append probes, affinity tags, or polymers via CuAAC in chemical biology workflows (cell-free labeling, bioconjugation of purified biomolecules).
Notes
Any biological testing or use should be conducted strictly as laboratory research. This product is not intended for diagnostic or therapeutic applications.
For live-cell or in vivo workflows, evaluate cytotoxicity and off-target reactivity independently; no such data are provided here.
Buffer Applications
Not typically applicable. 4-Ethynyl-1-methyl-1H-pyrazole is not a buffering agent, and no buffer recipes or pH ranges are relevant.
Practical note
If used in aqueous-organic reaction media (e.g., CuAAC), choose a buffer compatible with copper catalysis (e.g., phosphate or tris-derivatives as appropriate) and ensure the compound’s limited water solubility is addressed via co-solvents. No item-specific buffer guidance is provided.
Green Alternatives
Context: The molecule itself is a building block; “greenness” considerations mostly pertain to solvents and catalysts used with it.
Greener choices (literature/best practice)
Solvents
Replace DMF/DMAc/NMP with MeCN, 2-MeTHF, CPME, EtOAc, or bio-based alcohols where feasible.
For CuAAC, water or water/alcohol mixtures are effective and minimize VOCs.
For Sonogashira, 2-MeTHF or ethanol with suitable bases can reduce toxicity relative to amide solvents.
Catalysts/additives
Ligand-stabilized Cu(I) at low loading for CuAAC; consider copper-on-charcoal or supported catalysts to facilitate recovery.
Pd at ppm levels or heterogeneous Pd/C under flow can reduce precious metal usage in Sonogashira-type couplings.
Energy and workup
Microwaves or flow chemistry may shorten reaction times and lower energy demand.
Aqueous workups with phase separation over chromatography reduce solvent usage.
Illustrative comparison (general)
DMF (toxic, high boiling) vs 2-MeTHF (safer, renewable source): Similar polarity for many couplings; 2-MeTHF offers easier recovery and lower EHS burden.
DCM (halogenated) vs EtOAc (benign): For extractions and chromatography, EtOAc/hexane systems typically provide comparable separations with reduced hazards.
Trade-offs
Alternative solvents may alter rates/selectivity; re-optimize catalysts/bases and temperature accordingly.
Pharmaceutical Uses
No pharmacopeial status or excipient role is specified for this item; refer to CoA/Spec Sheet.
General considerations (research/manufacturing context only; no therapeutic claims)
As a heteroaromatic alkyne building block, it may serve in discovery-stage synthesis of APIs or intermediates, particularly where CuAAC-derived triazoles or yn-aryl linkages are desired.
For GMP or clinical manufacturing contexts, additional qualification (identity, purity profile, residual solvents/metals, and stability) would be required; such specifications are not provided for this catalog item.
Physical Properties
Item-specific specifications
Appearance: Not specified for this item; refer to CoA/Spec Sheet.
Molecular formula: Not specified for this item; refer to CoA/Spec Sheet. (Literature/computed for reference: C6H6N2)
Molecular weight: Not specified for this item; refer to CoA/Spec Sheet. (Literature/computed for reference: ~106.12 g/mol)
Other specifications (bp, mp, density, refractive index, UV cutoff, water/peroxide content, metal limits): Not specified for this item; refer to CoA/Spec Sheet.
General/literature expectations for this compound class (for planning only; verify experimentally)
Physical state: Small N-heteroaromatic alkynes are typically low-melting solids or high-boiling, low-viscosity liquids.
Solubility (qualitative, literature): Expected to be soluble in common organic solvents (e.g., DMSO, DMF, MeCN, EtOAc, THF, dichloromethane) and sparingly soluble in water due to aromatic/alkynyl character.
Acidity/basicity: Terminal alkyne C–H typically pKa ~24–26 in DMSO (literature, general). Pyrazole ring nitrogens confer weak basicity and H-bonding capability.
Notes
Use the item’s CoA/Spec Sheet for authoritative numeric properties relevant to your application.
If precise phase-transition data (mp/bp) are critical (e.g., for distillation or sublimation), confirm on receipt by DSC or capillary methods.
Quality and Grades
Item-specific quality information
Grade/Purity: Not specified for this item; refer to CoA/Spec Sheet.
Stabilizers/Inhibitors: Not specified for this item; refer to CoA/Spec Sheet.
Guidance for this compound class (general information)
Research grade heteroaromatic alkynes are commonly supplied at ≥95% GC/LC purity; verify by 1H NMR (diagnostic terminal alkyne singlet ~2–3 ppm in some solvents, and sp C–H ~3–4 ppm can vary) and by LC/MS.
If low-UV applications (e.g., photochemistry or trace analytics) are planned, request UV spec/trace impurity data.
Residual metal content: If subsequent metal-catalyzed couplings are intended, low background metals (Cu, Pd, Fe) can be advantageous. Request ICP data if critical. If not specified in the CoA, perform an in-house ICP screen when ppb–ppm levels matter.
Stabilization: Terminal alkynes generally do not require inhibitors, but minimizing copper contamination and oxygen exposure reduces Glaser-type dimerization during storage.
Documentation
For regulatory or quality systems, retain the item-specific CoA/Spec Sheet and SDS. Batch-specific analytical data (NMR, HPLC/GC, MS) should be used to qualify incoming material as needed.
Reaction and Applications
This molecule combines a terminal alkyne with a pyrazole ring, making it a versatile bifunctional synthon.
Key application areas (literature/general)
Copper-catalyzed azide–alkyne cycloaddition (CuAAC): The terminal alkyne enables rapid assembly of 1,4-disubstituted 1,2,3-triazoles under Cu(I). The pyrazole can modulate electronics/solubility, useful in probe/linker design.
Sonogashira cross-coupling: Couples the terminal alkyne with aryl/vinyl halides or triflates (Pd/Cu co-catalysis) to build conjugated yn-arenes or en-ynes; the N-heteroaryl core can fine-tune electronic properties in materials.
Glaser–Hay oxidative homocoupling: Dimerization to the diynyl-pyrazole under O2/Cu conditions, furnishing rigid spacers for molecular materials.
Nucleophilic addition to electrophiles after deprotonation: Formation of lithium/sodium acetylides that add to carbonyls or undergo alkylation; quench/alkylate to elaborate side chains.
Cycloadditions/annulations: [2+2+2] or gold-catalyzed alkyne activation can create fused or appended heterocycles incorporating the pyrazole.
Practical tips
Avoid adventitious copper and oxygen when monomeric alkyne is required; use chelating agents or degas and exclude air.
Bases for deprotonation: n-BuLi, LDA, or NaNH2 at low temperature in anhydrous ethers/hydrocarbons; titrate base to minimize over-reaction.
For Pd-catalyzed couplings near basic heterocycles, use robust ligands (e.g., XPhos, SPhos) and consider base choice (iPr2NH, Et3N, Cs2CO3) to balance ring coordination.
Use cases
Synthesis of heteroaryl–triazole conjugates for chemical biology (linkers/tags; research use only).
Construction of conjugated small molecules where pyrazole serves as an electron-withdrawing/coordination site.
Reaction Conditions
General literature conditions (guidance only; optimize for your system)
CuAAC (formation of 1,4-disubstituted triazoles)
Catalyst: CuSO4·5H2O (1–10 mol%) + sodium ascorbate (reducing agent) to generate Cu(I) in situ; or preformed CuI (1–5 mol%).
Solvent: tBuOH/H2O (1:1), MeOH/H2O, or DMF/H2O; 0.05–0.2 M.
Temperature/time: rt to 60°C, 0.5–12 h.
Notes: Use chelating ligands (e.g., TBTA) for sensitive substrates; minimize oxygen for best kinetics.
Sonogashira coupling (as alkyne partner)
Catalyst: Pd(PPh3)2Cl2 (1–3 mol%) with CuI (5–10 mol%) or copper-free variants with bulky phosphines.
Base: Et3N, iPr2NH, or Cs2CO3/K2CO3.
Solvent: DMF, DMAc, 2-MeTHF, THF, or toluene; 0.05–0.2 M.
Temperature/time: 25–80°C, 2–16 h.
Notes: Exclude air/moisture; heteroarenes may coordinate Pd—ligand choice (XPhos/SPhos) can improve turnover.
Glaser–Hay oxidative coupling
Catalyst: CuCl/CuI (5–10 mol%) + TMEDA or bipyridine under O2/air.
Solvent: DCM, MeOH, or toluene.
Temperature/time: rt to reflux, 2–24 h.
Notes: Control O2 to manage rate/selectivity; monitor to avoid overoxidation.
Formation of metal acetylides
Base: n-BuLi (1.0–1.2 equiv) or NaNH2 (1.5–2.0 equiv) at −78 to 0°C.
These conditions are literature-derived starting points and are not item-specific specifications.
Safety and Handling
Item-specific hazard information
GHS signal word, hazard statements, pictograms, and classification: Not specified for this item; refer to the SDS.
General safety guidance for terminal alkynyl N-heteroarenes (literature/consensus best practice)
Anticipated hazards: Combustible/flammable organic compound; may cause irritation to skin, eyes, and respiratory tract upon contact or inhalation of vapors.
PPE: Wear safety glasses or splash goggles, lab coat, and appropriate chemically resistant gloves (e.g., nitrile). Handle in a fume hood to minimize inhalation.
Handling: Avoid heat, sparks, and open flame. Ground and bond containers when transferring flammable liquids. Do not breathe vapors or dust; avoid contact with skin and eyes.
Incompatibilities: Strong oxidizers (risk of exotherm), strong bases (can deprotonate terminal alkyne to form reactive acetylides), and strong acids (possible ring protonation and exotherm). Copper salts can catalyze oxidative coupling (Glaser-type) of terminal alkynes under aerobic conditions.
Special risks: Terminal alkynes can undergo oxidative homocoupling; limit exposure to air/metal ions if monomer is desired. Some pyrazoles have moderate volatility; keep containers tightly closed.
First aid (overview; defer to SDS):
Inhalation: Move to fresh air; seek medical attention if symptoms persist.
Skin/eye contact: Rinse with water for at least 15 minutes; remove contaminated clothing; obtain medical advice if irritation continues.
Ingestion: Rinse mouth; do not induce vomiting; seek medical attention.
Always consult the product-specific SDS for definitive hazard, exposure limits, and emergency procedures.
Solvent Selection
Applicability: This product is a small, moderately polar, heteroaromatic terminal alkyne. Solvent choice is mainly relevant for reaction use and analytical handling.
Polarity and miscibility (general/literature)
Expected to dissolve well in polar aprotic organics (DMSO, DMF, DMAc, MeCN), chlorinated solvents (DCM, CHCl3), ethers (THF, MTBE), and esters (EtOAc). Limited water solubility likely.
CuAAC “click” reactions: tBuOH/H2O, MeOH/H2O, or DMF/H2O mixtures often balance solubility of azides and the alkyne; add ligand-stabilized Cu(I).
Sonogashira coupling (as alkyne partner): Polar amide solvents (DMF, DMAc, NMP) or amines (iPrNH2, Et3N as solvent/base) under inert gas; THF or toluene also used with suitable bases.
Base-mediated deprotonation to acetylides: THF, DME, or toluene under rigorously anhydrous conditions with strong bases (e.g., NaNH2, LDA, n-BuLi).
Purification: Normal-phase silica gel with hydrocarbon/EtOAc or DCM/MeOH gradients; protect from strongly basic eluents to avoid on-column reactions.
Analytical solvents
NMR: CDCl3, DMSO-d6, or CD3CN typically provide good solubility and well-resolved alkyne resonances.
Note: Verify solvent compatibility with your other reagents and catalysts; adjust based on the CoA-provided purity and any stabilizers if present.
Storage and Reconstitution
Item-specific storage/shipping
Storage conditions: Store at 2–8°C (from Product Data). Keep container tightly closed.
Shipped in: Wet ice (from Product Data).
General handling and stability guidance (not item-specific specs)
Protect from prolonged exposure to air and light to minimize oxidative dimerization of the terminal alkyne (Glaser-type). Where feasible, store under inert gas (N2/Ar) in amber glass.
If solidification occurs on cold storage, warm gently to ambient temperature before dispensing; if liquid, pre-cool receiving vessels to minimize losses from volatility.
Reconstitution: If supplied as a solid, dissolve in a dry, oxygen-free organic solvent appropriate to your application (e.g., anhydrous DCM, THF, MeCN, or DMSO). If any precipitation occurs on cold storage, redissolve with gentle warming and sonication as needed.
Freeze–thaw: Not typically applicable; avoid repeated warm–cold cycling that can introduce moisture/oxygen.
Research use note
For research use only (from Product Data). Verify stability and purity on receipt (e.g., 1H NMR, LC/MS) before critical applications.
Structure and Identity
Brief description: 4-Ethynyl-1-methyl-1H-pyrazole is a heteroaromatic pyrazole bearing an N1-methyl substituent and a terminal alkyne at the 4-position; it serves as a compact, bifunctional building block combining a basic azole ring and a reactive C≡CH handle.
Item-specific identifiers (from Product Data)
SKU: E170134
CAS: 39806-89-8
PubChem CID: 51138321
InChIKey: 310994 (as provided)
SMILES: Not specified for this item; refer to CoA/Spec Sheet.
Calculated/literature structural information (for reference; not item-specific specs)
Likely molecular formula (literature/computed): C6H6N2
Tautomerism: Pyrazoles can display N–H tautomerism; N1-methylation biases the ring toward a fixed N-methyl/N-aza configuration while the 4-ethynyl substituent is conjugated with the ring π-system.
2D structural description (verbal)
A five-membered pyrazole ring bearing a methyl group on the ring nitrogen (N1). At the carbon atom para to N1 (C4 by usual numbering), a linear ethynyl chain terminates in a hydrogen (–C≡CH). The second ring nitrogen (N2) is part of the aromatic system and not methylated.
Pyrazole ring: Aromatic, Lewis-basic nitrogens capable of coordinating metals; ring substitution patterns can be exploited via directed metalation/electrophilic substitution (literature-dependent).
Retrosynthetic value
Serves as a convergent node to append the pyrazole core to diverse fragments through the alkyne, then further elaborate (e.g., hydrogenation to alkyl linkers, hydroboration/oxidation to carbonyls, haloboration to vinyl halides, or cycloadditions to triazoles).
Representative transformations (literature examples; conditions not item-specific)
CuAAC with organic azides → 1,4-disubstituted 1,2,3-triazoles attached to pyrazole.
Hydrofunctionalizations: Hydroiodination or anti-Markovnikov hydroboration–oxidation of the alkyne → vinyl iodides or aldehydes/alcohols for further diversification.
Metalation at the terminal alkyne (e.g., n-BuLi) → nucleophilic additions to aldehydes/ketones; trap and quench for propargylic alcohols.
Target Specificity
Not applicable. This product is a small-molecule reagent, not a biological targeting agent or antibody. No antigen, epitope, clone, isotype, or species reactivity information applies.
Products are supplied to verified businesses, institutions, and qualified professionals for research and development use only. Not for use in humans, animals, diagnosis, or therapy.
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