Glutamine - C₅H₁₀N₂O₃ - [56-85-9] - ≥99,9% (Food grade supplement)
Triethylamine - TEA - C₆H₁₅N - [121-44-8] - ≥99,5%, for synthesis (Carl Roth)
Phtalic anhydride - C₈H₄O₃ - [85-44-9] - 99% (Fisher)
Acetic anhydride - C₄H₆O₃ - [108-24-7] - 99,5% (Sigma-Aldrich)
Toluene - C₇H₈ - [108-88-3] - ≥99,5%, ACS reagent (Sigma-Aldrich)
Tetrahydrofuran - THF - C₄H₈O - [109-99-9] - ≥99,5%, ACS reagent (Sigma-Aldrich)
1,4-Dioxane - C₄H₈O₂ - [123-91-1] - ≥99%, (Sigma-Aldrich)
Diethyl ether - C₄H₉O - [60-29-7] - ≥99% (Honeywell)
Cyclohexane - C₆H₁₂ - [110-82-7] - ≥99% (Sigma-Aldrich)

Phthalic anhydride (5.00g, 33.8mmol, 1.00 eq.) and L-glutamine (5.00g, 34.2mmol, 1.01 eq.) were ground together for 2 minutes in a blender. Next, the powder was weighed again (9.80g typically) and transferred into a single neck round bottom flask. The powder was then suspended in 55 mL of toluene. Triethylamine (NEt₃, 4.7mL, 33.8mmol, 1.00eq.) and acetic anhydride (Ac₂O, 9.5mL, 0.10mol, 3.00eq.) were added.
The reaction mixture was then heated to reflux and maintained refluxing at approximately 110^oC for 9 hours. After reflux, the reaction was quenched by allowing it to cool to room temperature and immersing the flask in an ice-salt bath for 30min at -5^oC. The product was recovered through simple vacuum filtration on a Gouch G3 funnel, resulting in a yellow-brown solid. It was subsequently washed with 10 mL of a saturated sodium bicarbonate solution in water and with 3 x 10 mL of diethyl ether.
The average yield was 2.40g. A small sample was dissolved in dioxane, spotted, and appeared to be pure on TLC with BuOAc 10: AcOH 5: n-BuOH 1 as the eluent (Rf: 0.87). It exhibited UV absorption at 254 nm and reacted with KMnO4 stain only while heated vigorously causing thalidomide to appear as black spots on a white background. Further purification of the sample could be achieved through flash column chromatography using the solvent mixture THF 4: Cyclohexane 6 (Rf: 0.60) or by dry column vacuum chromatography (DCVC) using a Cyclohexane:THF gradient.
Both the product before and after column chromatography displayed complete purity (≥95%) in ¹H-QNMR analysis . Any attempts at recrystallization using common solvent systems were found to be either low-yielding or ineffective in removing trace-colored impurities.

- The reaction mixture tends to go dark during the first our of reflux, it's a normal sign of the reaction's progress.
- Vigorous stirring is mandatory due the low solubility of the reagent in the solvent.
- The same reaction was conducted in microwave condition, without TEA and acetic anhydride using instead DMSO (2.5% w/w) as a catalist, the yield of thalidomide was lower compared to the reported method but reaction times are significantly reduced.
- Thalidomide is almost insoluble in most organic solvents (EtOAc, Et₂O, Hexane, DCM...). We observed it to be soluble in DMSO, DMF, pyridine, dioxane, THF and sparingly soluble in acetone, methanol and boiling ethanol.
- Thalidomide may be hydrolised in concentrated, strong, acqueos acids and bases.
- Polarimetric measurements revealed the product to be racemic. Anyways, for medical purposes, enantiopure Thalidomide isn't used. [2]
- FTIR spectra were collected on a "Cary 630 FTIR Spectrometer" equipped with an ATR module.
- NMR spectra were collected on "Varian Oxford 300MHz NMR" and "Varian Oxford 400MHz NMR".
- Procedure is based of an example reaction from the patent [1].
- We sincerely thank Professor M. Fochi, PhD.; S. Cerini, PhD. and Dr. Magdalena Medrzycka for the spectroscopic analysis.
- All the autors contributed equally to this work.

1H NMR (300 MHz, dmso) δ 11.11 (s, 1H), 8.01 – 7.77 (m, 4H), 5.23 – 5.06 (m, 1H), 3.01 – 2.77 (m, 1H), 2.64 – 2.50 (m, 2H), 2.15 – 1.93 (m, 1H).

[1] Rao, D. R. WO2009083724A1 - Processes for the preparation of thalidomide          - Google Patents. https://patents.google.com/patent/WO2009083724A1/en.

[2] Thalidomide: Uses, interactions, mechanism of action | DrugBank Online. DrugBank. https://go.drugbank.com/drugs/DB01041.
[3] Pharmakon. Spotify. https://open.spotify.com/show/5ZmnOq66QIEoTEdvCDN7TA.