Hydrochloric Acid → (2-Isopropyl-3-thioxo-2,3-dihydrobenzo[1,4]oxazin-4-yl)acetic acid

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Reaction Steps

To a solution of methyl 3,4-dihydro-2-isopropyl-3-thioxo-2H-1,4-benzoxazine-4-acetate (16.7 g) in methanol-dioxane (2:3, 150 ml), 2N NaOH (60 ml) was added dropwise in 10 minutes with stirring. After completion of the addition, stirring was continued for further 15 minutes, and the mixture was diluted with water, acidified with 2N HCl, and subjected to extraction with ethyl acetate. The extract was washed with water, and dried (MgSO4), from which the solvent was evaporated off. To the residue, hexane was added, to give crystals of 3,4-dihydro-2-isopropyl-3-thioxo-2H-1,4-benzoxazine-4-acetic acid. Yield was 12.6 g (79.2%). Recrystallization from isopropyl ether-hexane gave yellow prisms (mp 99°-100° C.). Yield was 11.2 g (70.6%).

Provenance & Evidence