Org. Synth. 1960, 40, 5
DOI: 10.15227/orgsyn.040.0005
2-AMINOFLUORENE
[2-Flurenylamine]
Submitted by P. M. G. Bavin
1
Checked by John C. Sheehan and Roger E. Chandler..
1. Procedure
In a
2-l. three-necked round-bottomed flask, equipped with a
mechanical stirrer (Note 1),
reflux condenser, and
dropping funnel, are placed
30 g. of pure 2-nitrofluorene, m.p.
157° [
Org. Syntheses, Coll. Vol. 2, 447 (1943)], and
250 ml. of 95% ethanol. After warming to 50° on a
steam bath,
0.1 g. of palladized charcoal catalyst (previously moistened with alcohol) is added
(Note 2) and the stirrer is started. About
15 ml. of hydrazine hydrate is added from the dropping funnel during 30 minutes
(Note 3). At this point an additional
0.1 g. of catalyst (previously moistened with alcohol) is added and the mixture is heated until the alcohol refluxes gently. After 1 hour the
nitrofluorene has dissolved completely and the supernatant liquor is almost colorless.
The catalyst is removed by filtration with gentle suction through a thin layer of Celite (Note 4). The flask is rinsed with 30 ml. of hot alcohol which is then used to wash the catalyst and Celite. The combined filtrates are concentrated under reduced pressure to about 50 ml. (Note 5) and then heated to boiling at atmospheric pressure. When 250 ml. of hot water is added slowly, 2-aminofluorene is precipitated as a colorless, crystalline powder. After cooling in an ice bath, the 2-aminofluorene is collected, washed with water, and dried in the dark in a vacuum desiccator. The product melts at 127.8–128.8° (Note 6) and amounts to 24–25 g. (93–96%).
2. Notes
1.
If the stirring is omitted, the
nitrofluorene takes longer to dissolve.
2.
A suitable catalyst is
10% palladium-on-charcoal, such as is supplied by Baker and Company, Inc., 113 Astor Street, Newark 5, New Jersey.
3.
The reaction is exothermic, and too rapid addition of the
hydrazine may cause the mixture to foam out of the condenser.
4.
Caution! The catalyst is often pyrophoric and should be kept moistened with alcohol. Celite is a diatomaceous earth filter aid.
5.
A
rotary evaporator is very convenient for the concentration since some of the amine invariably crystallizes toward the end.
3. Discussion
The preparation of
2-aminofluorene reported previously in
Organic Syntheses [
Coll. Vol. 2, 448 (1943)] we based on the method of Diels.
2The present procedure illustrates a general method for the reduction of aromatic nitro compounds to aromatic amines using
hydrazine and a hydrogenation catalyst such as
palladium,
platinum,
nickel,
iron, or
rethenium. The literature on this procedure up to 1963 has been reviewed.
3 In many instances the catalytic
hydrazine reductions give yields of amine equal to or better than those obtained by direct catalytic hydrogenation or other reduction methods. Both the apparatus and the procedure are simple. Under appropriate conditions the method may be used for the dehalogenation of aliphatic and aromatic halides,
3 a reaction for which
palladium appears to be a specific catalyst. The method has also been used for the reduction of
azobenzene and
azoxybenzene to
hydrazobenzene (
80–90%),
4 as well as for the synthesis of steroid aziridines by reduction of mesylate esters by vicinal azido alcohols (using
Raney nickel).
5
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
2-Flurenylamine
palladized charcoal catalyst
palladium-on-charcoal
ethanol (64-17-5)
iron (7439-89-6)
platinum (7440-06-4)
nickel,
Raney nickel (7440-02-0)
palladium (7440-05-3)
hydrazine hydrate (7803-57-8)
hydrazine (302-01-2)
Azoxybenzene (495-48-7)
Azobenzene (103-33-3)
2-Nitrofluorene (607-57-8)
2-Aminofluorene (153-78-6)
Nitrofluorene
rethenium
hydrazobenzene (122-66-7)
Copyright © 1921-, Organic Syntheses, Inc. All Rights Reserved