[OH-].C([N+](C)(C)C)C1C=CC=CC=1.[Cl:13][C:14]1[C:19]([CH3:20])=[CH:18][C:17]([OH:21])=[CH:16][C:15]=1[CH3:22].[C:23]([C:29](OC)=[O:30])#[C:24][C:25]([O:27]C)=[O:26].[OH-].[Na+].S(=O)(=O)(O)O>CO.O1CCOCC1>[Cl:13][C:14]1[C:19]([CH3:20])=[CH:18][C:17]2[O:21][C:24]([C:25]([OH:27])=[O:26])=[CH:23][C:29](=[O:30])[C:16]=2[C:15]=1[CH3:22]0.5 Parts of benzyl trimethylammonium hydroxide were added dropwise to a mixture of 156.6 parts of 4-chloro-3, 5-xylenol, 149.1 parts of dimethyl acetylene dicarboxylate and 30 parts of dioxan. The reaction mixture was heated for 1/2 hour on the steam bath, cooled, and basified with 320 parts of 25% aqueous sodium hydroxide solution. After addition of 100 parts of methanol the red solution was heated at reflux for 3 hours on the steam bath, cooled, and acidified with excess dilute sulphuric acid. The precipitated yellow solid was filtered, washed with a little water, and dried. The solid was added portionwise to 850 parts of stirred chlorosulphonic acid cooled to 0° C. When all the solid had dissolved, the dark red solution was added cautiously dropwise to excess ice-water. The precipitated solid was filtered, washed with water, and recrystallised from a dioxan aqueous ethanol mixture to give 157.1 parts of 6-chloro-5,7-dimethyl-4-oxo-4H-1-benzopyran-2-carboxylic acid as a colourless solid, melting point 289°-290° C.
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