This reaction probably proceeds through the intermediate formation of dithiocarbamate 1, the
nucleophilic opening of oxirane by 2 to give an intermediate dithiocarbamate derivative, namely, aminoethanol 3,
the spontaneous cyclization of 3 to give thiazolidine 4, and, finally, oxidative aromatization to give
3-benzyl-5-(4-nitrophenyl)thiazole-2(3H)-thione (5), which is a bright-yellow crystalline compound.
Elderfield [1] has described the formation of thiazolidinethiones from monoethanolamine derivatives
and carbon disulfide. However, oxiranes have not been used for the synthesis of thiazolidinethiones. An
interesting finding is the oxidative aromatization of intermediate thiazolidinethione 4 to give thiazolinethione 5.
This latter process can probably be attributed to the nitro group in the starting compound. The Skraup quinoline
synthesis is an analogous process, in which nitrobenzene is the oxidizing agent of the dihydro derivative formed
[3, 4].
In order to confirm the participation of the nitro group in the dehydrogenation of thiazolidinethione 4 to
give thiazolinethione 5, we carried out the analogous reaction, in which a twofold excess of nitrobenzene was
added in the final step. The product of the reduction of nitrobenzene, namely, aniline, was detected in the
reaction mixture by gas-liquid chromatography. The yield of thiazolinethione 5 in this case was increased almost
to 50%.
1
The IR spectrum was taken on an Avatar-320 spectrometer. The H NMR spectrum was taken on a
13
Bruker DRX500 spectrometer at 500 MHz in DMSO-d6 with TMS as the internal standard, while the C NMR
spectrum was taken on a Bruker AM300 spectrometer at 75 MHz in DMSO-d6. The electron impact mass
spectrum was taken on a Finnigan MAT Incos 50 mass spectrometer with direct inlet of the sample into the ion
source at 70 eV. The gas-liquid chromatography was carried out on a Kristall 5000.1 chromatograph with a
flame ionization detector at 200-250°C using a 30 m×0.25 mm Zebron-50 column with 50% phenyl polysil-
oxane, 50% dimethyl polysiloxane as the stationary phase, and helium as the gas carrier.
3-Benzyl-5-(4-nitrophenyl)thiazole-2(3H)-thione (5). A solution of carbon disulfide (0.76 g, 0.01 mol) in
ethanol (10 ml) was added with stirring to a solution of benzylamine (1.07 g, 0.01 mol) and triethylamine (1.01 g,
0.01 mol) in ethanol (15 ml) cooled to 0-5°C and stirred for about 2 h. Then, p-nitrophenyloxirane (1.65 g,
0.01 mol) was added, starting at room temperature and gradually warming to 45°C. The solvent was distilled off
after 5 h and the oily, dark-yellow residue was crystallized by adding hexane. Two recrystallizations gave 0.95 g
(29%) thione 5 as bright-yellow needles, mp 211-212°C (ethanol). IR spectrum (KBr), ν, cm-1: 1530 (–C=S), 1515,
1345 (NO2). 1H NMR spectrum, δ, ppm (J, Hz): 5.42 (2H, s, CH2); 7.38 (5H, m, Ar–H); 7.76 (2H, d, J = 8.9, 2CH–
Ar); 8.27 (2H, d, J = 8.9, 2CH–ArNO2); 8.55 (1H, s, N–CH). 13C NMR spectrum, δ, ppm: 52.05 (CH2); 123.71 (1C,
N–CH); 124.46 (2C-3, Ar–NO2); 125.86 (2C-2, 1C-4 Ar); 127.91, 128.00 (2C-2 Ar–NO2); 128.68 (2C-3 Ar);
132.09 (S–C); 135.31 (1C-1 Ar); 135.65 (1C-1 Ar–NO2); 146.42 (1C-4 Ar–NO2); 186.11 (N–C=S). Mass
spectrum, m/z (Irel, %): 328 [M]+ (45), 295 (28), 91 (100), 65 (37). Found, %: C 58.91; H 4.07; N 8.24.
C16H12N2O2S2. Calculated, %: C 58.52; H 3.68; N 8.53.
REFERENCES
1.
2.
3.
R. Elderfield, Heterocyclic Compounds [Russian translation], Vol. 5, Izd. Inos. Lit., Moscow (1960).
V. M. Byr'ko, Dithiocarbamates [in Russian], Nauka, Moscow (1984), 342 pp.
D. Barton and W. D. Ollis (editors), General Organic Chemistry [Russian translation], Vol. 8, Khimiya,
Moscow (1985).
4.
A. F. Pozharskii, V. A. Anisimova, and E. B. Tsupak, Laboratory Exercises in Heterocyclic Chemistry
[in Russian], Izd. Rostovsk. Gos. Univ., Rostov-on-the-Don, Russia (1988).
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