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Pictet-Spengler route to Praziquantel
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8th June 2010 @ 11:50
Preparation of a Cbz-protected amine as starting material for the Pictet-Spengler cyclisation – test reaction

Reaction Scheme


Table1


Hazard and Risk Assessment:
Reaction Class: 2
Hazards: Xn Harmful, C Corrosive, N Dangerous for Environment
Risk rating: U = Unlikely

Start time: 7:34 PM 08/06/2010
End time: 10:07 AM 09/06/2010

To a solution of MW7-2-27 (50 mg, 165 µmol) and Et3N (41.8 mg, 57.5 µL, 413 µmol) in dry DCM (2 mL) was added benzyl chloroformate (CbzCl) 31.0 mg, 28.3µL, 182 µmol) at 0°C. After 5 min the ice bath was removed and the solution was stirred for 14.5 h at room temperature.
- after 2 h TLC (EA = 100%, Rf = 0.52): about 50% conversion
- after 14.5 h: no change in the conversion of the starting material (~ 50%)

--> less reactive CbzCl? – using purified (distilled) CbzCl or higher amounts of the reagent
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Reaction Scheme
Table1