Abstract 2 can be pyrrolized to yield 3 a, which in turn may be hydrolyzed with HCl to 3 b. Acetylation of 3 a followed by a reaction with trifluoroacetic acid (TFA) gives 3 e. Elimination of ethanol from 3 a or of water from 3 e is not possible. Treatment of 1 a with pyridine/acetic anhydride and TFA or with acetic acid/acetic anhydride affords 4 a and 4 b, resp. Reaction of 4 b in benzene/p-toluenesulfonic acid for 2 hours yields both ethers 5I and 5II, whereas ...
![4-acetyl-3-hydroxy-3,4-dihydro-2H-benzo[1,4]oxazine Structure](https://image.chemsrc.com/caspic/308/70801-46-6.png)
