Pictet-Spengler route to Praziquantel

 

Testing various intermediates of PZQ (derivatives) with a achiral Bronstedt-acidic thiourea catalyst MW43-1 as pretest for chiral derivatives of the catalyst - NMR-monitored experiments





Hazard and Risk Assessment:
Reaction Class: 2
Hazards: T Toxic, X Irritant, C Corrosive
Risk rating: U = Unlikely

Start time: 4:30 PM 15/07/2010
End time: 10:30 PM 16/07/2010

General Procedure:
Each of the compound MW7, MW29-4, MW14, MW40-1 (75.0 µmol) shown in Table1 was solved in CDCl3 (~0.5 mL) in a NMR tube and MW43-1 (3.8 mg, 8.0 µmol, 10 mol%) was added and heated to 60°C for 18h.

MW44-1 – MW44-4: no conversion was monitored (by 1H NMR)

-> MeSO3H was added (5.2 µL of a 5% solution in CDCl3, 384 µg, 4.0 µmol, 5 mol%)
After 4 h at r.t. no conversion was monitored -> heated to 60°C

Comparison of the Reaction NMRs
Data: 1H NMR comparison MW44-1
Data: 1H NMR comparison MW44-2
Data: 1H NMR comparison MW44-3
Data: 1H NMR comparison MW44-4

Results:
No conversion of the starting material was observed