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14th March 2012 @ 09:49
PS = Pictet-Spengler

START: 15/03/12


Scheme KAB13-3

Hazard and Risk Assessment
As for KAB3-11 (here).

Previous/Related Experiments
AgOTf catalysed PS reaction to give the dimethoxy N-benzoyl PZQ analogue (KAB8-16)
AgOTf catalysed partial PS reaction to give the N-benzoyl PZQ analogue enamide (KAB17-2)
TfOH catalysed partial PS* reactions to give the enediamide intermediates of PZQ and the N-benzoyl analogue (KAB13-2 & KAB17-1)

Following Experiments

Chemical Information
N-(2,2-diethoxyethyl)-N-(2-oxo-2-(phenethylamino)ethyl)cyclohexanecarboxamide (1, KAB5-2) - SMILES: O=C(CN(C(C1CCCCC1)=O)CC(OCC)OCC)NCCC2=CC=CC=C2, InChI: InChI=1S/C23H36N2O4/c1-3-28-22(29-4-2)18-25(23(27)20-13-9-6-10-14-20)17-21(26)24-16-15-19-11-7-5-8-12-19/h5,7-8,11-12,20,22H,3-4,6,9-10,13-18H2,1-2H3,(H,24,26), InChIKey: QAUPSHBRPHFCJO-UHFFFAOYSA-N
4-(Cyclohexylcarbonyl)-1-(2-phenylethyl)-3,4-dihydro-2(1H)-pyrazinone (2, KAB13-3) - SMILES: O=C(N1/C=C\N(C(=O)C1)CCc2ccccc2)C3CCCCC3, InChI: InChI=1S/C19H24N2O2/c22-18-15-21(19(23)17-9-5-2-6-10-17)14-13-20(18)12-11-16-7-3-1-4-8-16/h1,3-4,7-8,13-14,17H,2,5-6,9-12,15H2, InChIKey: YQDMALZEUTXXHW-UHFFFAOYSA-N
Silver triflate - SMILES: C(F)(F)(F)S(=O)(=O)[O-].[Ag+], InChI: InChI=1S/CHF3O3S.Ag/c2-1(3,4)8(5,6)7;/h(H,5,6,7);/q;+1/p-1, InChIKey: QRUBYZBWAOOHSV-UHFFFAOYSA-M

The toluene used was degassed using the freeze-thaw method (liquid nitrogen) and dried with molecular sieves (4A). All glassware was oven dried prior to use.

KAB5-2 (438.0 mg, 1.083 mmol) was dissolved in toluene (43 mL) before the addition of AgOTf (27.0 mg, 0.105, 10 mol%). The reaction mixture was immediately placed in a pre-heated oil bath at 90 °C and reflux heated in the dark.
After 26 hours, the reaction mixture was removed from heat and allowed to cool. The mixture was diluted with EtOAc (50 mL) then washed with citric acid solution (0.5 M, 50 mL). The organic layer was separated and the acidic aqueous layer was basified with NaOH (2 M). The alkalike aqueous layer was the extracted with EtOAc (3 × 50 mL). The organic fractions were combined, dried over magnesium sulfate, filtered, then concentrated under reduced pressure to give crude KAB13-3 as a thick, dark brown oil.

Summary and Conclusion

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Scheme KAB13-3