Pictet-Spengler route to Praziquantel

 

Acid-mediated Pictet-Spengler of MW29 to give rac-PZQ MNR13-1 - comparing the rates of reaction versus the activated examples MNR11 and MNR12





Hazard and Risk Assessment:
As for MNR12-2

Procedure
MW29/MW36 (85 mg, 0.25 mmol) was stirred with methanesulfonic acid (1.6 mL, 25 mmol) at room temperature and after 1 hour (first TLC) all the starting material had been consumed. The reaction was quenched with saturated sodium carbonate and extracted with EtOAc (20 mL x2). The organic fractions were dried over magnesium sulfate, filtered and concentrated under reduced pressure.

Crude - 76 mg as a yellow oil that showed signs of slowly crystallizing after 24 hours

Crude 1H NMR did not match with MNR9-1 - peaks missing 4-6 ppm