Organic Syntheses, CV 3, 573
Submitted by C. V. Wilson, J. B. Dickey, and C. F. H. Allen.
Checked by George L. Evans and R. S. Schreiber.
1. Procedure
A
1-gal. autoclave (p. 80) (Note
1) is charged with
399 g. (1.29 moles) of technical sodium anthraquinone-α-sulfonate (Note
2),
45 g. (0.43 mole) of sodium chlorate,
780 g. (6.25 moles) of a 25% aqueous solution of methylamine, and 1.2 l. of water. The mixture is heated, with stirring, for 12 hours at 130–135° (Note
3). The heat is then shut off, but stirring is continued so that the product separates in an easily removable form. When cold, the autoclave is opened and the contents are removed; the material adhering to the walls is removed by water. The solid is filtered on a
13-cm. Büchner funnel. The red product is washed with two 500-ml. portions of hot water (70°) and dried in the air. The yield of
1-methylaminoanthraquinone, melting at
166–171° (Note
4), is
180–199 g. (
59–65%) (Note
5) and (Note
6).
2. Notes
1. A shaking autoclave employed for high-pressure hydrogenations may be used equally well, but the quantities taken must be reduced to
155 g. (0.5 mole) of sodium anthraquinone-α-sulfonate,
17.5 g. of sodium chlorate,
300 g. of a 25% aqueous methylamine solution, and 600 ml. of water. The checkers used a 2-gal. stirred autoclave (stainless steel).
2. A corresponding quantity of the potassium salt
1 can be utilized.
3. According to the checkers the heating time may be decreased to 8 hours if desirable.
4. The melting point varies slightly with the method of heating; if the bath is preheated to 160° before the sample is inserted, the melting point is
168–169.5° When taken in the ordinary way, the melting point is
166–171°. This product is sufficiently pure for most purposes. One recrystallization from
toluene raises the melting point 1°.
5. The yield depends upon the purity of the
sodium anthraquinone-α-sulfonate. Apparent yields of as high as
87% have been obtained. The checkers employed technical-grade material, which apparently resulted in an appreciable decrease in the yields of
76–80% reported by the submitters.
6.
α-Chloroanthraquinone2 can be used as a starting material. In this case, 433 g. (1.79 moles) is taken, together with
1.5 l. of pyridine,
600 ml. of 25% aqueous methylamine, and
2.5 g. of a copper salt. The product is washed with dilute
(2%) hydrochloric acid. The yield is
380–400 g. (
90–95%).
3. Discussion
This preparation is referenced from:
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