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9th April 2012 @ 22:32
START: 10/04/12
FINISH:

Background
Extending the reaction time. Also see synaptic leap post: here.




Hazard and Risk Assessment
As for KAB24-1 (here)

Previous Experiments
Synthesis of 6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydroisoquinoline (KAB21-2)
Synthesis of 1-phenyl-1,2,3,4-tetrahydroisoquinoline (KAB20-4)
Synthesis of 2-(3,4-dimethoxyphenyl)-N-(4-nitrobenzylidene)ethanamine (KAB23-1)
TFA mediated synthesis of 6,7-dimethoxy-1-(4-nitrophenyl)-1,2,3,4-tetrahydroisoquinoline (KAB24-1)
TFA mediated synthesis of 6,7-dimethoxy-1-(4-nitrophenyl)-1,2,3,4-tetrahydroisoquinoline (KAB24-2)

Following Experiments
TFA catalysed synthesis of 6,7-dimethoxy-1-(4-nitrophenyl)-1,2,3,4-tetrahydroisoquinoline (KAB24-4)

Chemical Information
2-(3,4-dimethoxyphenyl)-N-(4-nitrobenzylidene)ethanamine (1, KAB23-1) - SMILES: O=[N+]([O-])C1=CC=C(/C=N/CCC2=CC(OC)=C(OC)C=C2)C=C1, InChI: InChI=1S/C17H18N2O4/c1-22-16-8-5-13(11-17(16)23-2)9-10-18-12-14-3-6-15(7-4-14)19(20)21/h3-8,11-12H,9-10H2,1-2H3/b18-12-, InChIKey: LMBMXYXQVBPKHJ-PDGQHHTCSA-N.
6,7-dimethoxy-1-(4-nitrophenyl)-1,2,3,4-tetrahydroisoquinoline (2, KAB24-3) - SMILES: O=[N+]([O-])C1=CC=C(C2NCCC3=CC(OC)=C(OC)C=C32)C=C1, InChi: InChI=1S/C17H18N2O4/c1-22-15-9-12-7-8-18-17(14(12)10-16(15)23-2)11-3-5-13(6-4-11)19(20)21/h3-6,9-10,17-18H,7-8H2,1-2H3, InChIKey: GITFNMZGMQLGOX-UHFFFAOYSA-N.

Procedure
KAB23-1 (313 mg, 996 mmol) was dissolved in toluene (30 mL) before the addition of trifluoroacetic acid (0.15 mL, 2.0 mmol, 2 equiv.) at rt. The reaction mixture was reflux heated to 110 °C from 9:45.
After the addition of TFA
Reaction mixture (72 h)


Monitoring the Reaction Progress by TLC
TLC of reaction mixture (5 min)
TLC of reaction mixture (5 h)
TLC of reaction mixture (7 h)
TLC of reaction mixture (23 h)
TLC of reaction mixture (32 h)

TLC of reaction mixture (71 h)

TLC at 5 min: Eluted with 5%, MeOH/DCM, v/v; ninhydrin stain.
All other TLCs: Eluted with 15%, MeOH/DCM, v/v; ninhydrin stain.

Diluted with EtOAc (30 mL)
Quenched with saturated sodium bicarbonate (80 mL)
Extracted with EtOAc (2 × 50 mL)
Crude yield: 316 mg (101%).

Summary and Conclusion


References
[1] R. Gitto, M. L. Barreca, L. De Luca, G. De Sarro, G. Ferreri, S. Quartarone, E. Russo, A. Constanti, A. Chimirri, Journal of Medicinal Chemistry 2003, 46, 197.



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NOTES 10/04/12
- At 5 hours: reaction mixture contains both the suspected iminium ion and the cyclised product.

NOTES 12/04/12
- Flask weight: 47.1237 g
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Linked Posts
Attached Files
Scheme KAB24-3
After the addition of TFA
TLC of reaction mixture (5 min)
TLC of reaction mixture (5 h)
TLC of reaction mixture (7 h)
TLC of reaction mixture (32 h)
TLC of reaction mixture (23 h)
TLC of reaction mixture (71 h)
Reaction mixture (72 h)