New synthesis of benzo[b]furan-, benzo[b]thiophene- and benzo[b]-selenophene-3-acetic acids [1]

Full text of DOI:10.1023/A:1024781801125

Chemistry of Heterocyclic Compounds, Vol. 39, No. 4, 2003
LETTERS TO THE EDITOR
b
NEW SYNTHESIS OF BENZO[ ]FURAN-,
b
b
BENZO[ ]THIOPHENE- AND BENZO[ ]-
SELENOPHENE-3-ACETIC ACIDS
S. V. Tolkunov and A. I. Khizhan
Keywords: benzo[b]furan-, benzo[b]thiophene-, benzo[b]selenophene-3-acetic acids, new synthesis.
Heterylacetic acids hold interest as compounds with potential biological activity and reagents for fine
organic synthesis. Benzo[b]furan-3-acetic acid (1a) and benzo[b]thiophene-3-acetic acid (1b) are plant growth
stimulants. Benzo[b]-3-selenophene-3-acetic acid (1c) was recently found to have stronger auxin-like activity
than indolyl-3-acetic acid [1, 2]. While there are well-developed methods for the synthesis of acids 1a and 1b,
benzo[b]selenophene-3-acetic acid has not been readily available. The only method for the preparation of acid
1c was described by Laitem and Critiaens [3].
H
N
O
O
NH
CH2COOH
1) NaOH
O
+
2) H
X
X
1a–c
2a–c
1, 2 a X = O, b X = S, c X = Se
We propose
a
new synthesis for benzo[b]furan- (1a), benzo[b]thiophene- (1b), and
benzo[b]selenophene-3-acetic acids (1c), involving the alkaline hydrolysis of the corresponding
5-(3-heteryl)hexahydropyrimidine-2,4,6-triones (2a-c) obtained by the condensation of benzo[b]furan-3[2H]-
one, benzo[b]thiophene-3[2H]-one, and benzo[b]selenophene-3[2H]-one with barbituric acid according to
1
previous procedures [4, 5]. H NMR spectroscopy showed that compounds 2a-c in DMSO-d6 solution contain
about 65% of the keto form, as indicated by the 5-H signals at 5.37-5.50 ppm.
b
was obtained in 92% yield;
5-(3-Benzo[ ]furyl)hexahydropyrimidine-2,4,6-trione (2a)
1
mp 229-230°C (acetic acid). H NMR spectrum (200 MHz), δ, ppm, (J, Hz): 5.40 (1H, s, 5-H); 7.29 (1H, t,
J = 7.2, 6-H); 7.38 (1H, t, J = 7.7, 5-H arom); 7.49 (1H, d, J = 7.2, 7-H); 7.65 (1H, d, J = 7.7, 4-H); 7.95 (1H, s,
2-H); 10.90 (2H, br. s, NH); 11.56 (1H, br. s, OH enol). Found, %: C 59.31; H 3.48; N 11.40. C12H8N2O4.
Calculated, %: C 59.02; H 3.30; N 11.47.
__________________________________________________________________________________________
L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of
Ukraine, 83114 Ukraine, e-mail: tolkunov@uvika.dn. ua. Translated from Khimiya Geterotsiklicheskikh
Soedinenii, No. 4, pp. 624-625, April, 2003. Original article submitted November 6, 2002.
0009-3122/03/3904-0539$25.00©2003 Plenum Publishing Corporation
539

b
was obtained in 91% yield; mp 260°C
5-(3-Benzo[ ]thienyl)hexahydropyrimidine-2,4,6-trione (2b)
(acetic acid). 1H NMR spectrum, δ, ppm: 5.50 (1H, s, 5-H); 7.30-8.00 (5H, m, H arom); 10.90 (2H, br. s, NH);
11.51 (1H, br. s, OH enol). Found, %: C 55.61; H 3.24; N 10.60, S 12.40. C12H8N2O3S. Calculated, %: C 55.38;
H 3.10; N 10.76; S 12.32.
b
was obtained in 91% yield;
5-(Benzo[ ]selenophene-3-yl)hexahydropyrimidine-2,4,6-trione (2c)
1
mp 157-158°C (acetic acid). H NMR spectrum, δ, ppm: 5.37 (1H, s, 5-H); 7.20-7.56 (3H, 5-, 6-, 7-H arom);
7.90 (1H, s, 2-H); 8.00 (1H, m, 4-H); 10.83 (2H, br. s, NH); 11.45 (1H, br. s, OH enol). Found, %: C 46.75;
H 2.35; N 9.35; Se 25.54. C12H8N2O3Se. Calculated, %: C 46.92; H 2.63; N 9.12; Se 25.71.
b
was obtained in 68% yield; mp 89°C (heptane) (mp 89°C [6]).
Benzo[ ]furan-3-acetic Acid (1a)
Found, %: C 68.36; H 4.42. C10H8O3. Calculated, %: C 68.18; H 4.58.
was obtained in 66% yield; mp 108-109°C (heptane)
b
Benzo[ ]thiophene-3-acetic Acid (b)
(mp 108-109°C [7]). Found, %: C 62.23; H 4.27; S 16.53. C10H8O2S. Calculated, %: C 62.48; H 4.19; S 16.68.
was obtained in 58% yield; mp 149-150°C (cyclohexane)
b
Benzo[ ]selenophene-3-acetic Acid (1c)
1
(mp 150°C [3]). H NMR spectrum (DMSO-d6), δ, ppm, (J, Hz): 3.73 (2H, s, CH2); 7.28 (1H, t, J = 7.3, 6-H);
7.38 (1H, t, J = 7.7, 5-H); 7.72 (1H, d, J = 7.7, 4-H); 7.90 (1H, s, 2-H); 7.94 (1H, d, J = 7.3, 7-H); 12.18 (1H,
br. s, CO2H). Found, %: C 50.41; H 3.11; Se 33.28. C10H8O2Se. Calculated, %: C 50.23; H 3.37; Se 33.02.
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