Pictet-Spengler route to Praziquantel

 

START: 16/04/12
FINISH:



Hazard and Risk Assessment
As for KAB21-2 (here).

Previous Experiments
TFA mediated synthesis of 6,7-dimethoxy-1-(4-nitrophenyl)-1,2,3,4-tetrahydroisoquinoline (KAB24-3)
Synthesis of 6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydroisoquinoline (KAB21-2)
TFA mediated synthesis of 6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydroisoquinoline (KAB21-3)

Following Experiments

Chemical Information
N-[2-(3,4-Dimethoxyphenyl)ethyl]-1-phenylmethanimine (1, KAB19-2) SMILES: O(c1ccc(cc1OC)CC/N=C/c2ccccc2)C, InChI: InChI=1S/C17H19NO2/c1-19-16-9-8-14(12-17(16)20-2)10-11-18-13-15-6-4-3-5-7-15/h3-9,12-13H,10-11H2,1-2H3/b18-13+, InChIKey: HEYKSOUNCDDROU-QGOAFFKASA-N
6,7-Dimethoxy-1-phenyl-1,2,3,4-tetrahydroisoquinoline (2, KAB21-4) - SMILES: O(c1c(OC)cc3c(c1)C(c2ccccc2)NCC3)C, InChI: InChI=1S/C17H19NO2/c1-19-15-10-13-8-9-18-17(12-6-4-3-5-7-12)14(13)11-16(15)20-2/h3-7,10-11,17-18H,8-9H2,1-2H3, InChIKey: GZGZWZVAJDFXJK-UHFFFAOYSA-N


Procedure
16/04/12. KAB19-2 (365 mg, 1.36 mmol, 1 equiv.) was dissolved in toluene (35 mL) before the addition of trifluoroacetic acid (0.05 mL, 0.7 mmol, 0.5 equiv.). The reaction mixture was reflux heated to 110 °C from 14:50.


Monitoring the Reaction Progress by TLC

All TLCs were eluted with 15%, methanol/dichloromethane, v/v and stained with ninhydrin.

Crude yield (208 mg, 57%)

Summary and Conclusion

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NOTES 16/04/12
- KAB19-2 had crystallised since the last time it was used (in KAB21-3). Previously it was an oil.

Flask: 50.4746 g
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