[O-:1][C:2]#[N:3].[K+].Cl.S1(CCCC1)(=O)=O.[Cl:13][C:14]1[CH:15]=[C:16]([NH:23][CH2:24][C:25]([O:27][CH2:28][CH3:29])=[O:26])[C:17](=[CH:21][CH:22]=1)[C:18]([OH:20])=O>>[Cl:13][C:14]1[CH:15]=[C:16]2[C:17]([C:18](=[O:20])[NH:3][C:2](=[O:1])[N:23]2[CH2:24][C:25]([O:27][CH2:28][CH3:29])=[O:26])=[CH:21][CH:22]=1A total of 128 g of potassium cyanate and 144 g of hydrogen chloride are metered into 700 g of sulfolane at 15-20° C. over a period of 5 hours. For this, 14.4 g of hydrogen chloride are first passed in and 12.8 g of potassium cyanate are then added; this operation is repeated 10 times, until the entire amount of hydrogen chloride and potassium cyanate has been added. 117 g of 4-chloro-N-(ethoxycarbonylmethyl)anthranilic acid are then added at 45-50° C. in the course of 2 hours. The mixture is subsequently stirred for 15 minutes. The suspension is filtered and the residue is washed free from sulfolane and salt with water. After drying, 121 g (95%) of ethyl 1,2,3,4-tetrahydro-7-chloro-2,4-dioxoquinazolin-1-ylacetate are obtained.
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