Organic Syntheses, CV 5, 656
Submitted by H. M. Blatter, H. Lukaszewski, and G. de Stevens
1.
Checked by Wayland E. Noland and Kent R. Rush.
1. Procedure
A mixture of
1.44 g. (0.0099 mole) of indole-3-carboxaldehyde,
2 7.0 g. (0.053 mole) of diammonium hydrogen phosphate,
30 g. (30 ml., 0.34 mole) of 1-nitropropane, and
10 ml. of glacial acetic acid is refluxed for 12.5 hours. During the reflux period the pale-yellow mixture becomes dark red. The volatile reactants and solvent are removed under reduced pressure, and an excess of water is then added to the dark residue. After a short time, crude
indole-3-carbonitrile precipitates rapidly. It is separated by filtration and dried under reduced pressure; weight
1.20–1.34 g. (
85–95%). Crystallization from
acetone-hexane, with decolorization by activated
carbon, yields
0.68–0.89 g. (
48–63%) of fairly pure
indole-3-carbonitrile, m.p.
179.5–182.5° (Note
1).
2. Notes
1. The checkers obtained pure
indole-3-carbonitrile, m.p.
182–184°, by subliming the product at a pressure of 1.5 mm. (bath temperature 165–170°) and recrystallizing the sublimate from a mixture of
acetone and light
petroleum ether. The recovery was 84%.
3. Discussion
4. Merits of the Preparation
This synthetic process is applicable to the preparation of other aromatic nitriles from aldehydes. The submitters have used it to prepare
5-bromoindole-3-carbonitrile,
7-azaindole-3-carbonitrile,
p-chlorobenzonitrile,
3,4,5-trimethoxybenzonitrile, and
p-N,N-dimethylaminobenzonitrile.
9 There are several advantages to its use. They include (
a) readily available and inexpensive reagents, (
b) a simple, time-saving procedure, and (
c) fair to good yields of nitrile obtained by a
one-step method.
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