2-(Benzylamino)-1-(4-methoxyphenyl)-propane

2-(Benzylamino)-1-(4-methoxyphenyl)-propane is the most widely employed chiral amine building block in the industrial synthesis of the long‑acting β₂‑agonist formoterol fumarate and its derivatives. In the convergent manufacturing route, the (2R)‑enantiomer of 2-(Benzylamino)-1-(4-methoxyphenyl)-propane opens the chiral epoxide to form the secondary amine backbone with complete stereochemical fidelity. Because the racemic form of 2-(Benzylamino)-1-(4-methoxyphenyl)-propane is readily resolved using inexpensive chiral acids such as (S)‑mandelic acid, it provides a highly scalable entry to the single enantiomer needed for API synthesis. The N‑benzyl group of 2-(Benzylamino)-1-(4-methoxyphenyl)-propane not only protects the amine during coupling but also improves the crystallinity of the resolution salt, simplifying isolation and purification.

Product Parameters

Synthetic Route

Dissolve 1-(4-methoxyphenyl)prop-2-one (8.22 g, 50.0 mmol) and benzylamine (5.35 g, 50.0 mmol) in methanol, then add a 5% Pt/C catalyst (0.83 g). Stir the reaction mixture at 60 °C and carry out hydrogenation for 24 hours. Upon completion, remove the catalyst by filtration and evaporate the solvent under rotation to obtain the intermediate N-benzyl-1-(4-methoxyphenyl)prop-2-amine with a yield of 95%. The product was characterized by 1H NMR (400 MHz, CDCl₃): δ7.25 (ddd, J = 16.5, 11.1, 6; Chemical Book 8 Hz, 5H), δ7.07 (d, J = 8.5 Hz, 2H), δ6.83 (d, J = 8.5 Hz, 2H), δ3.86 (d, J = 13.3 Hz, 1H), δ3.79 (s, 3H), δ3.73 (d, J = 13.3 Hz, 1H), δ2.90 (dd, J = 13.0, 6.5 Hz, 1H), δ2.71 (dd, J = 13.5, 7.1 Hz, 1H), δ2.61 (dd, J = 13.5, 6.4 Hz, 1H), δ1.10 (d, J = 6.2 Hz, 3H). LC/MS (ESI m/z): 256.4 (M + H⁺).

FAQ

Q: What is the best solvent for the epoxide opening reaction?

A: Isopropanol or DMF at 60–80°C is commonly used. We can provide a technical note with typical conditions.

Q: Does the free base absorb CO₂ from air?

A: Like many secondary amines, it can slowly form a carbamate. Storage under nitrogen and using fresh material for critical reactions is recommended.

Application Scenarios

1.Formoterol/Aformoterol API Synthesis

The (2R)‑amine opens the epoxide intermediate to construct the N‑(2‑hydroxy‑2‑phenylethyl)‑propylamine backbone.

2.Chiral Resolution Studies

The racemic amine is a classic substrate for evaluating new chiral acids and resolution methodologies.

3.SAR Studies on LABAs

The N‑benzyl group can be substituted or modified to generate libraries of long‑acting β₂‑agonists.

4.Process Development

Used as a benchmark nucleophile for optimizing epoxide aminolysis under scalable conditions.

5.Impurity Marker Synthesis

The (2S)‑enantiomer is used to prepare the diastereomeric impurity for pharmacopoeial methods.

Contact Us

Need a reliable amine partner for your next β₂‑agonist campaign? Reach out to Cosperpharm today — we can provide a side‑by‑side comparison of our racemic and resolved specifications, along with a quote for your required volume, usually within the same business day.