Toluene → 5-Methyl-2h-thieno[2,3-d][1,3]oxazine-2,4(1h)-dione

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Reaction Steps

A mixture of ethyl 2-amino-4-methylthiophene-3-carboxylate (5 g, 0.03 mol) in methanol (25 ml) and aq. 2M sodium hydroxide (20.24 ml, 0.04 mol) was heated under reflux for 4 h. After cooling the solvents were evaporated, the residue dissolved in water (30 ml) and a 20% solution of phosgene in toluene (24 ml, 0.05 mol) added dropwise with ice cooling. After a further 30 min the solid which had precipitated was filtered, washed with water then ether, and dried to give the title compound 2.93 g (59%). 1H NMR (d6-DMSO) δ 2.31 (3H, s), 6.78 (1H, s), 12.50 (1H, br. s).

Provenance & Evidence