All Notebooks | Help | Support | About
This is a previous version of this entry. To view the latest click here. or to view all revisions click here.
29th January 2012 @ 23:46
*PS = Pictet-Spengler

*****Experiment still in progress with regular updates. Last updated 30/01/12.


Background
Repeat of procedure for the preparation of KAB8-5 with reduced catalyst loading.

Scheme%20KAB8-7.png



Hazard and Risk Assessment
As for KAB8-5 (here)

Previous Related Experiments
Controls for the AgOTf catalysed PS* to give the dimethoxy N-benzoyl PZQ analogue (KAB8-5 & KAB8-6)
The silver(I) triflate catalysed PS to give the dimethoxy N-benzoyl PZQ analogue (KAB8-4)

Following Experiments

Procedure

Preparation of stock acid: A 0.26 M solution of TfOH in toluene was prepared by mixing TfOH (~195 mg, 1.3 mmol) in toluene (5 mL). It was assumed the TfOH contributed negligible volume.

KAB8-7: MNR10-1 (153.9 mg, 0.336 mmol) was dissolved in toluene (32 mL) before the TfOH/toluene mixture (0.39 mL; TfOH = 30 mol%) was added at 12:30 at rt. The mixture was heated to 90 oC.

KAB8-8: The procedure was the same as for KAB8-7. MNR10-1 (94.8 mg, 0.207 mmol), toluene (32 mL), TfOH/toluene (0.12 mL; TfOH = 15 mol%). Added at 12:35 at rt, before heated to 90 oC.

Aliquot 1 (50 uL) extracted from both solutions at 12:40
Aliquot 2 (50 uL) extracted from KAB8-7 at 13:20

TLC of reaction mixtures (1)
TLC of KAB8-7 reaction mixture (2)


KAB8-8 taken off @ 12:50.
KAB8-7 taken off @ 13:25.

The reaction mixture was quenched with saturated sodium bicarbonate solution (50 mL) and the organic layer removed. The alkaline aqueous fraction was extracted with EtOAc (3 x 30 mL). The organic layers were combined, dried over magnesium sulfate, filtered, then concentrated under reduced pressure to give the crude products.

Crude KAB8-7:
Crude KAB8-8:


Conclusion


--------------------------------------------------------------
NOTES 30/01/12
- KAB8-8 with the lower catalyst loading probably finished first because of the way I added the acid. The acid solution was added into the MNR10-1/toluene solution with a long needle. The KAB8-7 acid was added to the flask, but not directly into the solution.
- The KAB8-8 mixture went to temperature faster; reached temperature in less than 2 min. The KAB8-7 reaction mixture did not reach 90 C. The reaction was quenched at ~80 C.
--------------------------------------------------------------
Linked Posts
Attached Files
Scheme KAB8-X
Scheme KAB8-X
TLC of reaction mixtures (1)
TLC of KAB8-7 reaction mixture (2)
KAB8-7 just removed from heat