[Cl:1][C:2]1[CH:16]=CC2C(=O)N3OC(C)CC3O[C:4]=2[CH:3]=1.[Cl:17][C:18]1[CH:27]=[C:22]([C:23]([NH:25][OH:26])=[O:24])[C:21]([OH:28])=[CH:20][CH:19]=1.C(=O)/C=C/C.Cl>C(O)(=O)C>[Cl:17][C:18]1[CH:19]=[CH:20][C:21]2[O:28][CH:4]([CH2:3][CH:2]([Cl:1])[CH3:16])[N:25]([OH:26])[C:23](=[O:24])[C:22]=2[CH:27]=1Prior 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 (3,2b) (1,3) benzoxazin-9-one and several methods for its manufacture.
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