A
1-l., round-bottomed flask equipped with a
stirrer, a
thermometer, a
dropping funnel, and a
reflux condenser to which is attached a
drying tube containing calcium chloride, is charged with
138 g. (131 ml., 1.00 mole) of resorcinol dimethyl ether and
200 ml. of dichloromethane. The solution is stirred, and a solution of
150 g. (1.06 moles) of chlorosulfonyl isocyanate (Note
1) in
100 ml. of dichloromethane is added with stirring at 15–20° over a 25-minute period. The amide
N-sulfonyl chloride separates as a crystalline solid, and the mixture is stirred for an hour at room temperature. The resulting mixture is cooled to 10–12° (Note
2) and
154 g. (2.1 moles) of N,N-dimethylformamide (Note
3) is added over a period of 5 minutes. The
cooling bath is removed and the temperature gradually rises to about 30°, then falls. After 1 hour the crystals dissolve and the reaction mixture is poured onto 200 g. of ice. After the ice has melted,
dichloromethane (150 ml.) is added, the mixture is shaken, and the organic layer is separated. The aqueous layer is extracted with
100 ml. of dichloromethane, and the organic phases are combined and washed with 100 ml. of water. The
dichloromethane is removed by distillation, giving a white solid that is triturated with 250 ml. of cold water, recovered by filtration, and dried, yielding
155–157 g. (
95–96%) of
2,4-dimethoxybenzonitrile, m.p.
91°. GC using a Chromosorb W column with 10%
butadiene sulfone as the stationary phase indicates that the product has a purity of 98%. The IR spectrum shows absorption at 2220 cm.
−1 attributable to the cyano group.