Hydrochloric Acid → 4H-1,3-Benzoxazin-4-one, 6-chloro-2-(2-chloropropyl)-2,3-dihydro-3-hydroxy-

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Prior to the present invention, 6-chloro-2-methyl-3,3a-dihydro-2H,9H-isoxazolo (3,2-b) (1,3) benzoxazin-9-one has been prepared by the reaction of 5-chlorosalicylhydroxamic acid (made from 5-chlorosalicylate and hydroxylamine) and crotonaldehyde in the presence of hydrogen chloride and glacial acetic acid to obtain 6-chloro-2-(2-chloropropyl)-2,3-dihydro-3-hydroxy-4H-1,3-benzoxazin-4-one. The latter compound was then cyclized to 7-chloro-2-methyl-3,3a-dihydro-2H,9H-isoxazolo (3,2-b) (1,3) benzoxazin-9-one. Said cyclization can be carried out using organic or inorganic bases in the appropriate solvent. U.S. Pat. No. 3,598,814 discloses and claims 7-chloro-2-methyl-3, 3a-dihydro-2H,9H-isoxazolo (3,2-b) (1,3) benzoxazin-9-one and several methods for its manufacture.

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