Sodium Hydroxide → 1H,2H,4H-thieno(3,2-d)(1,3)oxazine-2,4-dione

Participants

Reaction Steps

A mixture of 175 g (0.93 mol) of methyl 3-amino-2-thiophenecarboxylate hydrochloride, 1.8 l of n-butanol and 77 g of sodium hydroxide is heated to boiling under reflux for 30 minutes and the suspension obtained is concentrated. The resulting mixture of the sodium salt of 3-amino-2-thiophenecarboxylic acid and sodium chloride is treated with 800 ml of water, 280 ml of concentrated hydrochloric acid and 230 ml of tetrahydrofuran and at 15° to 25° phosgene is conducted through this mixture for 2.5 hours and subsequently air is conducted through the mixture for 15 minutes. The precipitated solid material is filtered off under suction, washed with water and dried. There is obtained 2H-thieno[3,2-d][1,3]oxazine-2,4(1H)-dione of melting point 220°-221°.

Provenance & Evidence