[CH3:1][C:2]1([CH3:14])[NH:7][C:6](=[O:8])[C:5]2[CH:9]=[C:10]([OH:13])[CH:11]=[CH:12][C:4]=2[O:3]1.C(=O)([O-])[O-].[K+].[K+].Cl[CH2:22][C:23](=[O:25])[CH3:24]>C(#N)C>[CH3:1][C:2]1([CH3:14])[NH:7][C:6](=[O:8])[C:5]2[CH:9]=[C:10]([O:13][CH2:22][C:23](=[O:25])[CH3:24])[CH:11]=[CH:12][C:4]=2[O:3]170 g of 2,3-dihydro-2,2-dimethyl-6-hydroxy-4H-1,3-benzoxazin-4-one are refluxed for 30 hours, whilst stirring, in 400 ml of acetonitrile with 100 g of potassium carbonate and 32 ml of chloroacetone. After the addition of a further 3.2 ml of chloroacetone, the reaction mixture is heated for a further 15 to 20 hours. The still warm reaction mixture is filtered, the residue thoroughly washed with acetone and the combined filtrate is concentrated by evaporation. The crystalline residue is recrystallised from toluene and yields 2,3-dihydro-2,2-dimethyl-6-(2-oxopropoxy)-4H-1,3-benzoxazin-4-one having a melting point of 125°-126°.
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