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Enantiomers of 2-methyl- and 2,4-dimethyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-2-carboxylic acid: Preparation by resolution, determination of absolute configuration, and Curtius rearrangement

✍ Scribed by Alenka Rutar; Urša Žbontar; Danijel Kikelj; Ivan Leban

Publisher
John Wiley and Sons
Year
1998
Tongue
English
Weight
260 KB
Volume
10
Category
Article
ISSN
0899-0042

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✦ Synopsis

Both enantiomers of 2-methyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-2carboxylic acid 2 and 2,4-dimethyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-2-carboxylic acid 3 were prepared via resolution of the corresponding racemic carboxylic acids with (R)-and (S)-1-phenylethylamine, respectively. Absolute configuration of (-)-(R)-2methyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-2-carboxylic acid was determined by X-ray crystallography. Curtius rearrangement of acyl azides prepared from enantiomers of these heterocyclic carboxylic acids carried out in benzyl alcohol afforded enantiomers of the corresponding benzyl carbamates, which upon hydrogenolysis gave racemic 2-amino-2-methyl-3,4-dihydro-2H-1,4-benzoxazin-3-one 4 and 2-amino-2,4-dimethyl-3,4dihydro-2H-1,4-benzoxazin-3-one 5. Chirality 10:791-799, 1998.

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