Preparation of 3,4-Methylenedioxypropiophenone using Methanesulfonic Acid (MSA)

[William Dampier]

Reaction scheme:

Synthesis:

1. Methanesulfonic acid (MSA, 288g) and propionic anhydride (156g) were charged into a 1 liter reaction flask.
2. The mixture was cooled to 0°C, and 122g of 3,4-methylenedioxybenzene (MDB) was added under stirring.
3. The reaction mass was maintained at 0°C to 5°C for 4 hours under stirring.
4. After completion of the reaction, the reaction mass was diluted with water, and the 3,4-methylenedioxypropiophenone product and unreacted MDB was extracted using toluene.
5. The toluene layer was distilled to recover 13g of unreacted MDB and obtain 137g of 3’,4’-methylenedioxypropiophenone.
6. The aqueous layer was distilled to recover 273g of MSA which was reused in subsequent batches and 85g of propionic acid.

Patent: US2022/0169588A1​