Synthesis of 1,4-oxathian-2-one, 5-methyl-1,4-oxathian-2-one, and 1,4-oxathiepan-2-one

Abstract

Intramolecular dehydration of 2-(2-hydroxyethylthio)acetic acid and of 2-(2-hydroxy-1-methylethylthio)acetic acid gives 1,4-oxathian-2-one and 5-methyl-1,4-oxathian-2-one, respectively. The precursor hydroxy-acids are formed by hydrolysis of the products of free radical addition of thioglycolic acid to vinyl acetate and propenyl acetate respectively. Free radical addition of thioglycolic acid to allyl chloride affords 2-(3-chloropropylthio)acetic acid, which is cyclised to 1,4-oxathiepan-2-one on treatment with potassium fluoride in glacial acetic acid. A mixture of 1,4-oxathiepan-2-one and 5-methyl-1,4-oxathian-2-one is produced on cyclodehydration of the mixture of 1 : 1 adducts formed by free radical addition of thioglycolic acid to allyl alcohol.