Russian Journal of General Chemistry, Vol. 72, No. 8, 2002, p. 1319. Translated from Zhurnal Obshchei Khimii, Vol. 72, No. 8, 2002, p.1404.
Original Russian Text Copyright
2002 by S. Shchelkunov, Yashnova, Li, A. Shchelkunov.
LETTERS
TO THE EDITOR
Improved Synthesis of Indoles
from 2,3-Epoxypropionic Acid Esters
S. A. Shchelkunov, N. I. Yashnova, M. L. Li, and A. V. Shchelkunov
Institute of Organic Synthesis and Coal Chemistry,
Ministry of Science and Higher Education of Kazakhstan, Karaganda, Kazakhstan
Received August 20, 2001
We previously [1] demonstrated the possibility of
synthesizing indoles in two steps by high-temperature
reaction of 2,3-epoxypropionic acid esters with
aniline, isolation of intermediate -hydroxy- -anilino
ester, and treatment of the latter with concentrated
sulfuric acid. In order to facilitate opening of the
oxirane ring, the reactions of 2,3-epoxypropionic acid
of the corresponding aniline hydrochlorides. We have
developed a one-pot procedure which combines the
following transformations: opening of the oxirane ring
in 2,3-epoxypropionic acid esters with formation of
-hydroxy- -anilino esters [reactions (1) and (2)];
their conversion into
-anilinoaldehydes [reac-
tion (3)], and cyclization of the latter to indoles [reac-
esters with anilines were carried out in the presence tion (4)].
+
3
RR C CH COOR + Ar NH Cl
RR C CHOH COOR
(1)
O
+
Ar NH Cl
2
(
2)
3)
RR C CHOH COOR + Ar NH2
RR C CHOH COOR
Ar NH
+
Ar NH Cl
2
(
RR C CHOH COOR
Ar NH
RR C CHO
Ar NH
R (R)
(4)
NHCRR CHO
R (R)
NH
1
2
-Phenylindole (I). To 12 ml of aniline we added
Yield 61%, mp 33 C. IR spectrum, , cm : 1610
(C Carom), 3475 (NH). The physical constants of
compounds I and II were consistent with published
data [1, 2].
first 2 ml of hydrochloric acid and then 3 ml of
methyl 3-phenyl-2,3-epoxypropionate. The mixture
was heated to the boiling point, kept for 6 h at that
temperature, neutralized with a 20% solution of KOH
to pH 8, and subjected to steam distillation. The dis-
tillate was extracted with diethyl ether, volatile frac-
tions were distilled off, and the residue was recrystal-
lized from petroleum ether alcohol. Yield 1.58 g
78%), mp 189 190 C. IR spectrum, , cm : 1605
C Carom), 3475 (NH). The structure of the product
was proved by independent synthesis from -bromo-
acetophenone and aniline. No depression of the
melting point was observed on mixing samples
obtained by the two methods. Following the same
procedure, we synthesized 2-n-propylindole (II).
The IR spectra were recorded on a UR-20 spec-
trometer.
REFERENCES
1
(
(
1
. Martynov, V.F. and Ol’man, G.A., Zh. Obshch. Khim.,
955, vol. 25, no. 8, p. 1561.
2. Pozharskii, A.F., Anisimov, V.A., and Tsupak, E.B.,
Prakticheskie raboty po khimii geterotsiklov
1
(Laboratory Works on the Chemistry of Heterocycles),
Rostov-on-Don: Rostov. Gos. Univ., 1988, p. 91.
1
070-3632/02/7208-1319$27.00 2002 MAIK Nauka/Interperiodica
Shchelkunov
