Ethanol → 4-Methoxyimino-5-methyl-6-bromothiochroman

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Reaction Steps

3.0 Grams (12 mmol) of 5-methyl-6-bromothiochroman-4-one and 1.9 g (23 mmol) of O-methylhydroxylamine hydrochloride were refluxed in a solvent mixture of 10 ml of ethanol and 10 ml of pyridine under heat for 30 minutes. The solvents were distilled off under reduced pressure, 50 ml of 5% hydrochloric acid was added, and a formed solid was recovered by filtration, washed with water and then dried to give 3.2 g (yield 93%) of 4-methoxyimino-5-methyl-6-bromothiochroman. (2) 1.1 Grams (46 mmol) of magnesium was dispersed in 10 ml of THF, and 2.2 g (20 mmol) of ethyl bromide was dropwise added under nitrogen current. The mixture was allowed to react for 10 minutes, and then a THF solution of 2.9 g (10 mmol) of the 4-methoxyimino-5-methyl-6-bromothiochroman obtained in the above (1) was gradually added at room temperature. The mixture was refluxed for 3 hours and then cooled to room temperature, and carbon dioxide gas was bubbled in for 1 hour. To the reaction mixture was added 5% hydrochloric acid, and the mixture was extracted with ether. An ether layer was extracted with a 5% potassium carbonate aqueous solution, and an aqueous layer was neutralized with concentrated hydrochloric acid. The neutralization product was extracted with ethyl acetate, and the extract was washed with a saturated sodium chloride aqueous solution. The washed extract was dried over sodium sulfate, and then the solvent was distilled off to give 1.6 g (yield 63%) of 4-methoxyimino-5-methylthiochroman-6-carboxylic acid.

Provenance & Evidence