Pictet-Spengler route to Praziquantel

 

Based on results from MNR11-4, extended reaction times are going to be studied.





Hazard and Risk Assessment:
As for MNR11-3

Procedure

MNR11-11
MNR8-2(50 mg, 0.11 mmol) and 1,1’-Binaphthalene-2,2’-disulfonic acid, MW54-3 (5 mg, 0.01 mmol) DCM (2 mL) was heated at reflux.

1st LCMS sample taken after 4 days

After another 24 hours (5 days in total) the reaction was quenched with saturated sodium carbonate and extracted with EtOAc (10 mL x3). The organic fractions were dried over magnesium sulfate, filtered and concentrated under reduced pressure.

Crude - 35 mg

MNR11-12
MNR8-2(50 mg, 0.11 mmol) and 1,1’-Binaphthalene-2,2’-disulfonic acid, MW54-3 (5 mg, 0.01 mmol) toluene(2 mL) was heated at reflux.

1st LCMS sample taken after 4 days

After another 24 hours (5 days in total) the reaction was quenched with saturated sodium carbonate and extracted with EtOAc (10 mL x3). The organic fractions were dried over magnesium sulfate, filtered and concentrated under reduced pressure.

Crude - 36 mg

LCMS after work up is significantly different than direct from the reaction mixture. This shows complete conversion to the product with no traces of hemiaminal or starting materials. The only other observed spots are impurities also seen in the LCMS of the starting material.