(S)-2-Amino-2-(3-bromophenyl)ethanol: Handling & Use Protocol

(S)-2-Amino-2-(3-bromophenyl)ethanol is a enantiomerically enriched chiral amino alcohol that serves as a versatile building block in asymmetric synthesis, chiral resolution, and the preparation of pharmaceutical intermediates.

Chemical Name

(S)-2-Amino-2-(3-bromophenyl)ethanol

SKU

A734554

Molecular Formula

C8H10BrNO

Molecular Weight

216.08 g/mol

Stereochemistry

(S)-configuration at the benzylic carbon

Key Functional Groups

Primary amine (–NH2) and primary alcohol (–OH)

Typical Application

Chiral auxiliary, pharmaceutical intermediate, asymmetric catalyst ligand precursor

Materials and Safety Precautions

(S)-2-Amino-2-(3-bromophenyl)ethanol (Aladdin SKU A734554) contains both a primary amine and a primary alcohol on a brominated aryl scaffold. Before use, consult the Safety Data Sheet (SDS) for complete hazard information.

• Personal Protective Equipment (PPE): Wear nitrile gloves, a laboratory coat, and safety goggles. Work in a well-ventilated fume hood to avoid inhalation of dust or aerosols.
• Storage: Store in a tightly sealed container under cool, dry conditions (2–8 °C recommended) away from oxidizing agents and strong acids or bases. Protect from moisture and light to prevent degradation.
• Waste Disposal: Dispose of all waste in accordance with institutional and local regulatory requirements for amine-containing halogenated organic compounds.
• Materials Required: Analytical balance, amber glass vials, inert-atmosphere (N2 or Ar) glove bag or Schlenk line (if moisture sensitivity is a concern), appropriate organic solvents (e.g., anhydrous methanol, DCM, DMF), and pH indicator paper or meter.

Stock Solution Preparation

Prepare stock solutions under inert atmosphere if long-term stability is required. The compound is generally soluble in polar protic and aprotic solvents including methanol, ethanol, DMSO, and DMF.

1. Determine target concentration: For most synthetic applications, a stock concentration of 0.1–0.5 M is practical. For biological screening assays, prepare a 10–50 mM stock in DMSO.
2. Weigh accurately: Tare a clean, dry vial on an analytical balance. Transfer the required mass of (S)-2-Amino-2-(3-bromophenyl)ethanol using a spatula. Example: To prepare 10 mL of a 0.1 M solution, weigh 216.1 mg (MW ≈ 216.08 g/mol).
3. Dissolve: Add approximately 80% of the final solvent volume, cap the vial, and mix gently (vortex or magnetic stirring at room temperature) until complete dissolution is observed.
4. Adjust to final volume: Transfer quantitatively to a volumetric flask and make up to the final volume with solvent.
5. Label and store: Label with compound name, concentration, solvent, date, and preparer's initials. Store at –20 °C under inert atmosphere for extended shelf life.

Note: Verify purity and enantiomeric excess (ee) by chiral HPLC or optical rotation measurement before use in enantioselective reactions.

Representative Applications and Reaction Protocol

(S)-2-Amino-2-(3-bromophenyl)ethanol is widely employed in synthetic chemistry owing to its bifunctional nature and defined stereocenter. Key applications include:

1. Use as a Chiral Auxiliary or Ligand Precursor

The amino alcohol scaffold can coordinate to metal centers, making it a precursor for chiral oxazoline ligands or amino alcohol-derived catalysts used in asymmetric addition reactions (e.g., diethylzinc additions to aldehydes). To prepare an oxazoline derivative, react the compound with an appropriate nitrile or imidate under mild acid catalysis.

2. Aryl Bromide Cross-Coupling

The aryl bromide moiety is amenable to palladium-catalyzed cross-coupling reactions (Suzuki–Miyaura, Negishi, Buchwald–Hartwig) to introduce diverse aryl, vinyl, or amino substituents at the 3-position of the phenyl ring, enabling rapid library synthesis of chiral amino alcohol analogs.

• Use standard Pd(PPh3)4 or Pd(dppf)Cl2 catalyst systems.
• Protect the amine (e.g., as Boc carbamate) and alcohol (e.g., as TBS ether) prior to cross-coupling to avoid catalyst poisoning.
• Deprotect under standard conditions post-coupling.

3. Pharmaceutical Intermediate Synthesis

Chiral amino alcohols of this class serve as intermediates toward beta-adrenergic ligands, antifungal agents, and other biologically active molecules. The (S)-stereochemistry is often required for optimal receptor binding.

Quality Control and Analytical Characterization

Before initiating sensitive enantioselective reactions, confirm the identity and quality of (S)-2-Amino-2-(3-bromophenyl)ethanol using the following analytical methods:

• Chiral HPLC: Use a chiral stationary phase column (e.g., Chiralpak IA or AD-H) to determine enantiomeric excess (ee). Typical mobile phase: hexane/isopropanol with 0.1% diethylamine.
• Optical Rotation: Measure [α]D at 20 °C in a suitable solvent (e.g., MeOH or EtOH) and compare with literature values to confirm (S)-configuration. Flag: specific rotation value not available in source material — verify from supplier CoA or primary literature.
• 1H NMR: Confirm structural identity. Key signals include the benzylic CH (δ ~4.5–4.8 ppm), NH2 (broad), and CH2OH (δ ~3.5–3.8 ppm).
• TLC: Use silica gel plates with a suitable eluent (e.g., DCM/MeOH/NH3 9:1:0.1) and ninhydrin staining for amine detection.
• Karl Fischer Titration: Assess water content if moisture-sensitive reactions are planned.

Accept lots with ee ≥98% and purity ≥97% (by HPLC area normalization) for enantioselective applications. Consult the Certificate of Analysis (CoA) supplied with each lot for specific values.

Troubleshooting

The following table summarizes common issues encountered when working with (S)-2-Amino-2-(3-bromophenyl)ethanol and suggested remedies:

• Poor solubility: Switch to a more polar solvent (DMSO, DMF) or gently warm the solution to 40–50 °C. Avoid prolonged heating which may cause racemization or decomposition.
• Low ee in asymmetric reactions: Verify the ee of the starting material by chiral HPLC before use. Ensure reaction temperature is controlled and that no racemization-promoting conditions (strong base, high temperature) are present.
• Catalyst poisoning in cross-coupling: Protect the amine and alcohol functionalities before Pd-catalyzed steps. Use Boc protection for the amine and silyl ether (TBS or TMS) for the alcohol.
• Degradation on storage: Ensure the container is tightly sealed and stored under inert atmosphere at the recommended temperature. Discard lots showing discoloration or off-odors.
• Inconsistent optical rotation: Ensure the measurement solvent and concentration match the reference conditions exactly. Residual moisture or solvent impurities can affect the reading.

Frequently asked questions

What solvents are recommended for dissolving (S)-2-Amino-2-(3-bromophenyl)ethanol?

The compound is generally soluble in polar protic solvents such as methanol and ethanol, as well as polar aprotic solvents including DMSO and DMF. For sensitive reactions requiring anhydrous conditions, use freshly dried and degassed solvents. Solubility in non-polar solvents such as hexane or diethyl ether is limited.

How should (S)-2-Amino-2-(3-bromophenyl)ethanol be stored to maintain enantiomeric purity?

Store the compound in a tightly sealed container under an inert atmosphere (nitrogen or argon) at 2–8 °C or –20 °C for long-term storage. Protect from moisture, light, and strong oxidants. Verify enantiomeric excess by chiral HPLC periodically, especially if the material has been stored for extended periods or exposed to non-ideal conditions.

Can the aryl bromide group be used directly in palladium-catalyzed cross-coupling without protecting the amine and alcohol?

While some cross-coupling reactions can tolerate free amines and alcohols, the unprotected amino alcohol functionalities may coordinate to palladium, causing catalyst poisoning and reduced yields or selectivity. It is strongly recommended to protect both the amine (e.g., as Boc carbamate) and the alcohol (e.g., as TBS ether) before performing Pd-catalyzed coupling steps, then deprotect under standard conditions after the coupling is complete.

What is the significance of the (S)-configuration in this compound?

The (S)-configuration defines the absolute stereochemistry at the benzylic carbon bearing both the amino and hydroxymethyl groups. In asymmetric synthesis and pharmaceutical applications, the specific enantiomer can determine the chiral sense of induction in catalytic reactions or the pharmacological activity and receptor selectivity of drug candidates. Using the correct enantiomer is critical for reproducible, enantioselective outcomes.

References

1. Nugent, T. C. (Ed.). Chiral Amine Synthesis: Methods, Developments and Applications. Wiley-VCH, 2010.
2. Noyori, R.; Kitamura, M. Enantioselective addition of organometallic reagents to carbonyl compounds: chirality transfer, multiplication, and amplification. Angewandte Chemie International Edition, 1991, 30, 49–69. doi:10.1002/anie.199100491
3. Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chemical Reviews, 1995, 95, 2457–2483. doi:10.1021/cr00039a007

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.