Acetic Acid → 2-(4-Chlorophenyl)-4,5-dimethyl-1,3-oxazol 3-oxide

1.00 g (9.89 mmol) of diacetyl monoxime and 1.53 g (10.88 mmol) of 4-chlorobenzaldehyde are initially charged in 2 ml (34.94 mmol) of glacial acetic acid. With ice-cooling, hydrogen chloride gas is then introduced into the reaction mixture for 30 min 10 ml of diethyl ether are then added to the reaction mixture. A precipitate is formed, which is filtered off with suction and washed twice with in each case 2 ml of diethyl ether. The precipitate is suspended in about 5 ml of water, and the suspension is made basic using aqueous ammonia. The suspension is then extracted four times with in each case 10 ml of dichloromethane. The combined organic phases are dried over magnesium sulphate, and the solvent is removed on a rotary evaporator. Without further purification, the product obtained in this manner is used for the subsequent step.