Triethylamine → Isopropyl 4-fluoro-2-methyl-5-[(6-methyl-2,3-dihydro-1,4-oxathiine-5-carbonyl)amino]benzoate

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Reaction Steps

Thionyl chloride (4.7 g, 0.040 mole) was added to stirred mixture of 5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxylic acid (6.0 g, 0.037 mole) and methylene chloride (50 ml). The mixture was stirred overnight at room temperature, then evaporated under reduced pressure. The solid residue, crude 5,6-dihydro-2-methyl-1,4-oxathiin-3-carbonyl chloride, was dissolved in methylene chloride (50 ml) and the chilled solution treated dropwise over about 1 hour with a solution of 1-methylethyl 5-amino-4-fluoro-2-methylbenzoate (7.9 g, 0.037 mole) and triethylamine (3.9 g, 0.039 mole) in methylene chloride (50 ml). The reaction mixture was left stirring overnight at room temperature and worked up by washing in sequence with water (50 ml), dilute hydrochloric acid (3.5%, 50 ml), water (50 ml), dilute sodium hydroxide (2%, 25 ml) and water (50 ml). Evaporation of the solvent left a solid residue. Recrystallization from 100% ethanol (60 ml) gave yellow-tan crystals, m.p. 119°-122° C. (7.6 g, 57% yield).

Provenance & Evidence