Selective cleavage of Arylacetates to Phenols
Morpholine (1.1 mL, 0.012 mol) was added to a solution of ethyl 4-(6-acetoxy-3-oxo-2H-benzo[b][1,4]oxazin-4(3H)-yl)butanoate in 10 mL THF and the resulting mixture was refluxed for 1 h. The progress of the reaction was monitored by thin layer chromatography (TLC). The reaction mixture was evaporated, diluted with ethyl acetate, washed with water, dried over sodium sulfate and evaporated under reduced pressure to give ethyl 4-(6-hydroxy-3-oxo-2H-benzo[b][1,4]oxazin-4(3H)-yl)butanoate, isolated as a brown oil (1.2 g, 99% yield, NMR complies).
How did you remove the N-acetyl morpholine? Did it actually wash away with water, from EtOAc?
milkshake
October 2, 2008 at 7:57 am
Yes. The byproduct N-acetyl morpholine was washed away with water. I could not see its peaks in NMR. Otherwise I would have gone for a column chromatography or use piperazine in which case N-acetyl piperazine could be washed away easily with dilute HCl.
pmgb
October 2, 2008 at 3:44 pm
I have a question Milkshake. Did you ever use BBr3.(CH3)2S complex for O-demethylation. I have used BBr3.(CH3)2S complex in two cases but it seems like it does not work. Recently I tried to O-demethylate ethyl 4-methoxy-2-nitrobenzoate by refluxing it with 1.2 eq of BBr3.(CH3)2S complex in 1,2-dichloroethane for 12 h. The solution turned black but I recovered most of the starting material back. I suspect the quality BBr3.(CH3)2S complex from Aldrich. Why does BBr3.(CH3)2S complex fume so much when you open the bottle?
pmgb
October 2, 2008 at 4:03 pm
I was always using neat BBr3, uncomplexed, in DCM on ice bath, then warm up to RT.
BBr3 It is one smoky nasty brownish badass liquid. I think the smoke comes from the water fog forming upon hydratation of anhydrous HBr. All anhydrous volatile strong acids smoke, and so do halides that hydrolyse instantly, SiCl4, TiCl4 etc
milkshake
October 2, 2008 at 8:34 pm