Enantioselective Hydrogenation of dehydro-PZQ and derivatives

 

Experiments on the oxidation of N-benzoyl-PZQ to the enamide by molten sulfur.
See related experiments on rac-PZQ: Sulfur melt data smogasbord



Hazard and Risk Assessment:


Start time: 5:15 PM 18/04/2011

MW59-1:
N-benzoyl-PZQ (40 mg, 131 µmol, M.W. 306.4 g/mol) and sulfur (8.4 mg, 262 µmol, 2 eq., M.W. 32.1 g/mol) were heated at 180°C for 5 min.

MW59-2:
N-benzoyl-PZQ (40 mg, 131 µmol, M.W. 306.4 g/mol) and sulfur (8.4 mg, 262 µmol, 2 eq., M.W. 32.1 g/mol) were heated at 180°C for 15 min.

MW59-3:
N-benzoyl-PZQ (40 mg, 131 µmol, M.W. 306.4 g/mol) and sulfur (8.4 mg, 262 µmol, 2 eq., M.W. 32.1 g/mol) were heated at 180°C for 30 min.

MW59-4:
N-benzoyl-PZQ (40 mg, 131 µmol, M.W. 306.4 g/mol) and sulfur (16.8 mg, 524 µmol, 4 eq., M.W. 32.1 g/mol) were heated at 180°C for 5 min.

MW59-5:
N-benzoyl-PZQ (40 mg, 131 µmol, M.W. 306.4 g/mol) and sulfur (16.8 mg, 524 µmol, 4 eq., M.W. 32.1 g/mol) were heated at 180°C for 15 min.

MW59-6:
N-benzoyl-PZQ (40 mg, 131 µmol, M.W. 306.4 g/mol) and sulfur (16.8 mg, 524 µmol, 4 eq., M.W. 32.1 g/mol) were heated at 180°C for 30 min.

TLC (ethyl acetate, stain: ninhydrin, Ceric ammonium molybdate, Ceric ammonium molybdate, KMnO4)


Results:
All experiments showed left-over starting material -> reaction time has to be extended, see related reactions:
Scale-up: Oxidation of N-benzoyl-PZQ by sulfur (MW59-7)
Repetition: Oxidation of N-benzoyl-PZQ by sulfur (MW59-8)

References:
[1] Spectral and Chemical Properties of Pyrazino-[2,1-a]-isoquinolin-4-one Derivatives, K. Kiec'-Kononowicz, Arch. Pharm. 1989, 322,795-799. DOI: 10.1002/ardp.19893221104.