To a solution of
41.6 g. (0.25 mole) of purified 2,3-dimethoxybenzaldehyde (Note
1) in
150 ml. of 95% ethanol is added
23.4 g. (0.75 mole) of methylamine in 50 to 75 ml. of water (Note
2). The mixture is heated to boiling and placed in a
500-ml. heavywalled bottle (Note
3), and
6 g. of Raney nickel catalyst is added (Note
4). The bottle is connected to a
low-pressure hydrogenation apparatus,
2 the system is flushed with
hydrogen, and the mixture is shaken with
hydrogen at an initial pressure of 45 lb. until
0.25 mole of hydrogen is absorbed and the absorption ceases (Note
5).
After the completion of the reduction the catalyst is removed by filtration and the alcohol is evaporated on the steam bath. To the resulting syrupy solution is added about
85 ml. of 3N hydrochloric acid (sufficient to make the solution acid to Congo red paper). The solution is extracted with three
50-ml. portions of ether. The aqueous layer is made alkaline with
50 ml. of 6N sodium hydroxide, and the amine layer is separated. The aqueous layer is extracted with three
50-ml. portions of ether, and the extracts are combined with the amine layer. The
ether solution is dried overnight with
solid potassium hydroxide and is filtered to remove suspended matter; the flask is rinsed with
25 ml. of ether. The
ether is removed on a steam bath, and the amine is distilled under reduced pressure from a
modified Claisen flask having a 15-cm. indented column. The
N-methyl-2,3-dimethoxybenzylamine distils at
120–124°/8 mm. and is obtained in a yield of
39–42 g. (
86–93%) (Note
6) and (Note
7).