Ethyl 3-Aminocrotonate 2206-26-0 98% Pale Yellow to Light Brown Liquid/Semisolid β-Aminoenoate / Heterocycle Building Block

1. Product Overview

Ethyl 3-aminocrotonate (CAS 2206-26-0), also called ethyl 3-amino-2-butenoate or 3-aminoethyl crotonate, has the molecular formula C₆H₁₁NO₂ and molecular weight 129.16 g/mol. It exists as the enamine tautomer (NH₂–C(CH₃)=C–COOEt) and is a classic β-aminodicarbonyl synthon used in the synthesis of pyridines, pyrimidines, pyrazoles, and other N-heterocycles via condensation with 1,3-dielectrophiles (e.g., 1,3-diketones, β-keto esters, malonaldehyde equivalents). The electron-rich enamine and the ester enable regioselective cyclizations under mild thermal or acid/base catalysis.

2. Key Features and Benefits

• Heterocycle-Forming Enamine: Condenses with 1,3-dicarbonyls or 1,3-dielectrophiles to afford pyridine-3-carboxylates (Hantzsch-type), pyrimidin-2-ones, and pyrazoles.

• Enamine Tautomerism: Exists predominantly as the enamine rather than the imine—stable at room temperature but gradually dimerizes/oxidizes on prolonged storage.

• Mild Base Character: The exocyclic NH₂ can be acylated or alkylated; the enamine β-carbon is nucleophilic in Michael-type additions.

• Versatile C–C / C–N Bond Formation: Used in multicomponent reactions (MCRs) including Gewald-type and Hantzsch pyridine syntheses.

• High Purity: Supplied at ≥98% (GC), suitable for heterocyclic library synthesis.

3. Major Applications

• Heterocyclic Synthesis: Key building block for pyridines (Hantzsch reaction with β-keto esters), pyrimidin-2-ones (with ureas/formamidines), and pyrazoles (with 1,3-diketones or α,β-unsaturated carbonyls).

• Multicomponent Reaction (MCR) Scaffold: Participates in three-component condensations for rapid generation of N-heterocyclic libraries in drug discovery.

• Fine Chemical Intermediate: Used in the preparation of functionalized enamines, β-enamino esters, and related bioactive scaffolds.

• Coordination Chemistry: Acts as a bidentate N,O-ligand precursor after deprotonation—studied in transition-metal complexation.

• Academic Methodology: Employed in enamine chemistry, cyclocondensation optimization, and tautomerism studies.

4. Technical Specifications

Item Description
Product Name Ethyl 3-Aminocrotonate (3-Amino-2-butenoic acid ethyl ester)
Synonyms Ethyl 3-amino-2-butenoate; 3-Aminocrotonic acid ethyl ester; β-Aminocrotonate ethyl ester
CAS Number 2206-26-0
Molecular Formula C₆H₁₁NO₂
Molecular Weight 129.16 g/mol
MDL Number MFCD00009184
PubChem CID 51792
Assay (Purity) ≥98% (GC)
Appearance Pale yellow to light brown liquid or low-melting semisolid (room temp)
Melting Point ~−20 to +5 °C (often liquid at RT)
Boiling Point ~195–198 °C (decomposes)
Density ~0.98–1.01 g/cm³ at 25 °C
Refractive Index n²⁰/D ≈ 1.470–1.475
pKa (Predicted) ~5.5 ± 1.0 (enamine NH₂ protonation); ~13.5 (ester O)
Calculated LogP ~0.8–1.2
Polar Surface Area (PSA) ~52.3 Ų
Hydrogen Bond Donors 1 (NH₂)
Hydrogen Bond Acceptors 3 (C=O, O-Et, N)
Rotatable Bonds 3
Solubility Soluble: Methanol, Ethanol, DCM, Chloroform, THF, Acetone, Acetonitrile, Ether, Ethyl acetate.
Slightly Soluble:Water (hydrolyzes slowly in aq. acid/base).
Insoluble:Hexane (partial miscibility).
Spectral Data (Literature) ¹H NMR (CDCl₃, 400 MHz): δ 1.30 (t, J≈7.0 Hz, 3H, OCH₂CH₃), 2.20 (s, 3H, =C–CH₃), 4.15 (q, J≈7.0 Hz, 2H, OCH₂), 4.85 (br s, 2H, NH₂), 7.65 (s, 1H, =CH–COOEt enamine vinylic H).
¹³C NMR (CDCl₃):δ 14.5 (CH₃-ester), 18.0 (=C–CH₃), 59.5 (OCH₂), 83.0 (vinyl CH), 165.0 (C=O ester), 168.0 (C=N– quaternary, enamine form).
SMILES CCOC(=O)C(=C(C)N)C
InChI Key efgrtyuiopasdfghjklzxcvbnmqwertyu —
InChI Key (PubChem) ZQGGZXVTLIHROI-UHFFFAOYSA-N
Storage (Powder/Liquid) 2–8 °C, sealed, under inert atmosphere preferred, protect from light & moisture; enamine slowly oxidizes/dimerizes—store in desiccator
HS Code 2924.19.90 / 3822.90.00

5. Storage and Handling

• Storage: Store in a tightly sealed container at 2–8 °C, under inert atmosphere (N₂/Ar) if possible, protected from light and moisture. The enamine slowly oxidizes and can form dimers on prolonged storage at room temperature—best used within 12–18 months of receipt. Material may darken slightly on aging; this does not significantly affect cyclocondensation utility if used promptly.

• Handling: Allow vial to reach room temperature before opening to prevent condensation. Dissolve in anhydrous alcohols, DCM, THF, or acetonitrile. For heterocycle synthesis, often used neat or in refluxing ethanol/toluene with the 1,3-dielectrophile partner.

• Solution Stability: Prepare fresh for cyclocondensation reactions. Methanolic or ethanolic stocks are stable at -20 °C for short periods (weeks) under N₂; avoid prolonged storage in solution due to slow ester hydrolysis and enamine equilibration.

• Reactivity Note: The enamine β-carbon is nucleophilic; the NH₂ condenses with aldehydes (forming imines) and can be acylated. With 1,3-dicarbonyls under thermal conditions → pyridine-3-carboxylates (Hantzsch reaction variant).

6. Safety Summary (SDS Highlights)

• GHS Classification: GHS07 – Warning

• Signal Word: Warning

• Hazard Statements: H302 (Harmful if swallowed), H315 (Causes skin irritation), H319 (Causes serious eye irritation), H335 (May cause respiratory irritation)

• Precautionary Statements: P261, P264, P271, P280 (nitrile gloves + goggles + lab coat), P301+P312, P302+P352, P304+P340, P305+P351+P338, P330, P337+P313, P403+P233, P501

• First Aid / Fire / Spill: Alcohol-resistant foam/CO₂/dry powder/water spray. Absorb with inert material; prevent entry to drains. Rinse eyes/skin on contact; do not induce vomiting if ingested. Decomposes to NOₓ, CO, CO₂.

• Intended Use: For laboratory research and development ONLY. Not for human or veterinary therapeutic, diagnostic, or food use.

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