4-Bromo-2-ethoxythiazole: Handling & Synthesis Protocol

4-Bromo-2-ethoxythiazole is a halogenated, ethoxy-substituted thiazole building block widely employed in medicinal and synthetic organic chemistry as a versatile intermediate for cross-coupling reactions and heterocyclic scaffold elaboration.

CAS Number

Not specified in source material — see product page

Molecular Formula

C5H6BrNOS

SKU / Product Code

B183078

Functional Group

Aryl bromide, ethoxy group, thiazole ring

Primary Application

Cross-coupling reactions (Suzuki, Negishi, Buchwald-Hartwig) and heterocyclic synthesis

Storage Recommendation

Store in a cool, dry, well-ventilated area away from light and moisture

Overview and Chemical Properties

4-Bromo-2-ethoxythiazole (SKU: B183078) is a five-membered aromatic heterocycle containing both sulfur and nitrogen atoms in the thiazole ring, with a bromine substituent at the 4-position and an ethoxy group at the 2-position. The presence of the C–Br bond makes this compound an excellent electrophilic partner in transition-metal-catalyzed coupling reactions. The electron-donating ethoxy group at the 2-position modulates the ring's electronic density, influencing both reactivity and selectivity in downstream transformations.

The compound is a solid or low-melting material (exact melting point should be confirmed on the certificate of analysis) and is sensitive to prolonged exposure to moisture, light, and strong oxidizing agents. Its molecular formula is C₅H₆BrNOS, giving a calculated molecular weight of approximately 208.08 g/mol.

Safety, Storage, and Handling

Personal Protective Equipment (PPE): Handle 4-Bromo-2-ethoxythiazole in a well-ventilated fume hood. Wear appropriate chemical-resistant gloves (nitrile recommended), safety goggles, and a laboratory coat at all times during handling. Avoid inhalation of dust or vapors.

Storage: Store the reagent in a tightly sealed container in a cool (2–8 °C recommended, confirm on label), dry, and dark environment. Keep away from strong acids, strong bases, and oxidizing agents. Shelf life should be verified on the product label and certificate of analysis.

Disposal: Dispose of all waste in accordance with local, regional, and national regulations governing halogenated organic waste. Do not pour into drains.

First Aid: In the event of skin contact, wash thoroughly with soap and water. For eye contact, rinse immediately with plenty of water and seek medical advice. If inhaled, move to fresh air and consult a physician if symptoms persist.

Protocol: Cross-Coupling Reaction Using 4-Bromo-2-ethoxythiazole

The following is a general guideline for using 4-Bromo-2-ethoxythiazole as an aryl bromide coupling partner in palladium-catalyzed Suzuki–Miyaura cross-coupling. Specific reaction conditions should be optimized for each substrate combination.

Materials Required:

• 4-Bromo-2-ethoxythiazole (B183078, Aladdin Scientific)
• Arylboronic acid or boronic acid ester (1.0–1.5 equiv)
• Palladium catalyst (e.g., Pd(PPh₃)₄ or Pd(dppf)Cl₂, 2–5 mol%)
• Base (e.g., K₂CO₃ or Cs₂CO₃, 2.0–3.0 equiv)
• Solvent (e.g., DMF/H₂O 4:1, or dioxane/H₂O 4:1)
• Inert atmosphere (N₂ or Ar)

General Procedure:

1. Charge a dry Schlenk flask or round-bottom flask with 4-Bromo-2-ethoxythiazole (1.0 equiv) and the boronic acid coupling partner (1.2 equiv).
2. Add the palladium catalyst (2–5 mol%) and the base (2.5 equiv) to the flask.
3. Add the degassed solvent mixture, seal the flask, and purge with N₂ or Ar for 10–15 minutes.
4. Heat the reaction mixture to 80–100 °C with stirring and monitor by TLC or HPLC until the starting material is consumed (typically 4–16 hours).
5. Cool the reaction to room temperature, dilute with ethyl acetate, and wash with saturated NH₄Cl solution followed by brine.
6. Dry the organic layer over anhydrous Na₂SO₄, filter, and concentrate under reduced pressure.
7. Purify the crude product by column chromatography (silica gel) using an appropriate solvent gradient.

Note: Reaction times, temperatures, and catalyst loadings are general estimates. Optimization is required for each specific substrate pair. Always consult the current safety data sheet before performing this protocol.

Quality Control and Analytical Characterization

Upon receipt of 4-Bromo-2-ethoxythiazole (B183078), users are advised to verify the identity and purity of the reagent using the following analytical techniques before use in critical synthetic steps:

• NMR Spectroscopy: ¹H NMR and ¹³C NMR should be consistent with the expected structure. Key signals include the aromatic thiazole C–H proton, the –OCH₂– quartet (ethoxy methylene), and the –CH₃ triplet of the ethoxy group.
• GC or HPLC Purity: Purity should meet or exceed the specification stated on the certificate of analysis (CoA). Typical research-grade purity is ≥95% (confirm on CoA).
• Mass Spectrometry: The molecular ion should show the characteristic isotope pattern for a mono-bromo compound (approximately 1:1 ratio for M and M+2 ions).
• Melting Point: Confirm against the value reported on the CoA.

Retain the CoA supplied with each lot for traceability and record-keeping purposes. Contact Aladdin Scientific technical support if analytical data deviate significantly from specifications.

Applications in Medicinal and Synthetic Chemistry

4-Bromo-2-ethoxythiazole serves as a versatile building block in multiple areas of chemical research:

• Medicinal Chemistry: Thiazole-containing scaffolds are prevalent in bioactive compounds and approved pharmaceuticals. The ethoxy group at C-2 can be selectively transformed (e.g., via hydrolysis to the corresponding thioamide or nucleophilic displacement) to introduce pharmacophoric diversity.
• Palladium-Catalyzed Cross-Coupling: The C4–Br bond is reactive toward Suzuki–Miyaura, Negishi, Sonogashira, and Buchwald–Hartwig coupling reactions, allowing rapid elaboration of the thiazole core with aryl, alkyl, alkynyl, or amino substituents.
• Directed Metalation: The ethoxy substituent may direct ortho-metalation strategies for further functionalization of the heterocyclic ring.
• Fragment-Based Drug Discovery: The compound's small size and bifunctional handle make it suitable as a fragment or linker unit in library synthesis.

Disclaimer: Applications listed are based on general knowledge of thiazole halide chemistry. Specific experimental outcomes should be validated by the end user.

Frequently asked questions

What is the recommended solvent for dissolving 4-Bromo-2-ethoxythiazole?

4-Bromo-2-ethoxythiazole is generally soluble in common organic solvents such as DCM, THF, DMF, acetonitrile, and ethyl acetate. It has limited solubility in water. Always confirm solubility empirically and consult the CoA or SDS for further guidance.

Can 4-Bromo-2-ethoxythiazole be used in Buchwald–Hartwig amination reactions?

Yes, aryl bromides including halogenated thiazoles are well-established substrates for Buchwald–Hartwig amination using palladium catalysts and appropriate phosphine ligands. Reaction conditions should be optimized for specific amine partners and desired yields.

How should I store 4-Bromo-2-ethoxythiazole to maximize shelf life?

Store the compound in a tightly sealed container under an inert atmosphere (N₂ or Ar), in a cool and dark location, protected from moisture. Refrigeration (2–8 °C) is recommended. Always check the specific storage instructions on the product label and CoA supplied with your lot.

What palladium catalyst is most suitable for Suzuki coupling with this compound?

Common palladium catalysts such as Pd(PPh₃)₄ and Pd(dppf)Cl₂ are frequently used for Suzuki–Miyaura coupling of aryl bromides. The choice of catalyst depends on the electronic and steric properties of both coupling partners, and optimization is recommended for best results.

Is a Certificate of Analysis available for B183078?

Yes, Aladdin Scientific provides a Certificate of Analysis (CoA) for each lot of B183078. The CoA includes purity data, analytical characterization, and storage conditions. You can request the CoA through the Aladdin Scientific website or by contacting customer support.

References

1. Joule, J.A.; Mills, K. Heterocyclic Chemistry, 5th ed.; Wiley-Blackwell: Oxford, 2010. (General reference for thiazole chemistry)
2. Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chem. Rev. 1995, 95, 2457–2483. doi:10.1021/cr00039a007
3. Hartwig, J.F. Palladium-Catalyzed Amination of Aryl Halides and Related Reactions. Acc. Chem. Res. 1998, 31, 852–860. doi:10.1021/ar970282g

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