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

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Reaction Steps

Thionyl chloride (4.4 g, 0.037 mole) was added to a stirred mixture of 5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxylic acid (5.0 g, 0.031 mole) and methylene chloride (50 ml). The mixture was warmed to 35°-40° C. for about 3 hours, left stirring overnight at room temperature, and 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 solution treated dropwise at 5°-10° C. over 2 hours with a solution of butyl 5-amino-2-chlorobenzoate (6.1 g, 0.031 mole) and triethylamine (3.6 g, 0.036 mole) in methylene chloride (50 ml). The reaction mixture was stirred at room temperature for a further 3 hours and then 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 (50ml). Evaporation of the solvent left an oil, which slowly solidified. Recrystallization from methanol (50 ml) gave beige crystals, m.p. 71°-73° C. (4.7 g, 41% yield).

Provenance & Evidence