Water → 2,6-Dimethylanisole

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A suspension of 2,6-dimethylphenol (19.5 g), iodomethane (31 ml) and potassium carbonate (33.2 g) in dimethylformamide (200 ml) was stirred at 60° C. for 10 hours. The reaction mixture was poured into water (300 ml) and the mixture was extracted with ethyl acetate. The extract was washed with a saturated aqueous sodium chloride solution and dried over anhydrous magnesium sulfate. The solvent was evaporated and the obtained residue was purified by silica gel column chromatography (eluent:hexane) to give 2-methoxy-m-xylene (12 g) as a colorless oil. A suspension of 2-methoxy-m-xylene (5.1 g), N-bromosuccinimide (4.2 g) and bezoyl peroxide (229 mg) in carbon tetrachloride (50 ml) was heated under reflux for 3 hours. The insoluble material was filtered off and the filtrate was concentrated under reduced pressure. The obtained residue was purified by silica gel column chromatography (eluent:hexane-ethyl acetate (10:1)) to give a yellow solid (5.4 g). The obtained yellow solid (5.4 g) and hexamethylenetetramine (5.1 g) were dissolved in acetic acid-water (1:1, 16 ml) and the mixture was heated under reflux for 2 hours. To the reaction mixture was added concentrated hydrochloric acid (6 ml) and the mixture was heated under reflux for 15 minutes. The reaction mixture was extracted with ethyl acetate. The extract was washed with water, an aqueous sodium hydrogencarbonate solution and a saturated aqueous sodium chloride solution, and dried over anhydrous magnesium sulfate. The solvent was evaporated and the obtained residue was purified by silica gel column chromatography (eluent: hexane-ethyl acetate (5:1)) and crystallized (hexane-ethyl acetate (5:1)) to give 2-methoxy-3-methylbenzaldehyde (1.2 g) as yellow crystals. Subsequently, the title compound was prepared from 2-methoxy-3-methylbenzaldehyde, 3-aminopyrazole and ethyl 3-ketohexanoate in the same manner as in Example 25.

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