In conclusion, we would note that, with the presence of acrylonitrile fragments, the obtained (2E,2'E)-
2,2'-(1,2,4-selenadiazole-3,5-diyl)bis(3-arylacrylonitriles) can undergo further functionalization in order to
prepare novel derivatives of the rare 1,2,4-selenadiazole heterocyclic system.
1
IR spectra were recorded in nujol on an IKS-29 spectrophotometer. H NMR spectra were acquired on
Bruker DPX-400 (400 MHz) and DRX-500 (500 MHz) instruments using DMSO-d6 with TMS as internal
standard. HPLC-MS analysis was carried out on an Agilent 1100 chromatograph with UV diode array (215,
254, and 265 nm) and Agilent LS/MSD SL detectors with ES-API ionization. Elemental analysis was performed
on a Carlo-Erba 1106 Elemental Analyzer apparatus. Melting points were measured on a Kofler hot stage
apparatus and were not corrected. Purity of the prepared compounds was monitored by TLC on Silufol UV-254
plates using 1:1 acetone–hexane as eluent and iodine vapor or UV visualization. The selenoamide 2c [12, 13]
was obtained by a known method. Selenoamides 2a,b were prepared by a similar method, but contained up to
20% of arylidenemalononitrile and dimer impurities. This prevented the determination of melting point or
performing an elemental analysis (purification was unsuccessful due to the instability of these compounds).
Since the indicated impurities did not hinder the synthesis of selenadiazoles 1a-c, the compounds 2a-c were
oxidized without additional purification.
(E)-2-Cyano-3-(4-hydroxyphenyl)prop-2-eneselenoamide (2a). Freshly prepared cyanoselenoacet-
amide [18] (300 mg, 2.03 mmol) and 4-hydroxybenzaldehyde (250 mg, 2.05 mmol) were added to distilled
water (15 ml), that had been prepared by boiling under an argon stream and cooling to 20°C. The suspension
obtained was heated under an argon stream at about 50°C until homogenisation, and Et3N (1 drop) was added.
The product was stirred at this temperature for 1 min, and the precipitated selenium was removed by filtration
under argon. The filtrate was left in a closed flask for 24 h at 20°C. The red-brown precipitate was filtered off
and washed with water and diethyl ether. Yield 460 mg (90%). 1H NMR spectrum (400 MHz), , ppm (J, Hz):
3
3
6.92 (2Н, d, J = 8.4, H Ar); 7.90 (2Н, d, J = 8.4, H Ar); 8.06 (1H, s, Ar–CH=); 10.10 (1H, br. s) and 10.79
(1H, br. s, NH2); 10.67 (1H, br. s, ОН).
(E)-2-Cyano-3-(3,4-Dimethoxyphenyl)prop-2-eneselenoamide (2b) was prepared from the cyano-
1
selenoacetamide and veratral by the general method [12, 13]. Yield 91%. Brown powder. H NMR spectrum
(400 MHz), , ppm (J, Hz): 3.79 (3Н, s, OCH3); 3.85 (3Н, s, OCH3); 7.15 (1Н, d, 3J = 8.1, H Ar); 7.59 (1Н, d,
3J = 8.1, H Ar); 7.70 (1Н, s, H Ar); 8.08 (1H, s, Ar–CH=); 10.16 (1H, br. s) and 10.86 (1H, br. s, NH2).
(2E,2'E)-2,2'-(1,2,4-Selenadiazole-3,5-diyl)bis(3-arylacrylonitriles) (1a-c) (General Method). The
unsaturated selenoamide 2a-c (0.7 mmol) and DMSO (0.2 ml, 3.0 mmol) were introduced into a 25-ml beaker,
followed by acetone (7-10 ml), and the mixture was heated to full dissolution. A 30% solution of HCl (0.2 ml,
1.9 mmol) was added dropwise with stirring, the solution cleared instantly and elemental selenium precipitated,
along with evolution of Me2S. The mixture was brought to reflux, rapidly filtered through a filter paper to
remove the elemental selenium, and the precipitate was washed with boiling acetone (2 ml). Cooling the
combined filtrates resulted in crystallization of the product. The suspension was maintained in an open beaker
for 48 h at 25°C. The precipitate was then filtered off, then washed with EtOH and Et2O. In the case of the
selenoamide 2a, evaporation of the acetone left an oily residue, which was recrystallized from EtOH.
Analytically pure selenadiazoles 1a-c were thus obtained.
(2E,2'E)-2,2'-(1,2,4-Selenadiazole-3,5-diyl)bis[3-(4-hydroxyphenyl)acrylonitrile] (1a). Yield 40 mg
1
(27%). Yellow-green crystals; mp >250°C (EtOH). Rf 0.41. IR spectrum, , cm-1: 2220 (C≡N). H NMR
3
3
spectrum (400 MHz), , ppm (J, Hz): 6.96 (2H, d, J = 8.5, H Ar); 6.99 (2H, d, J = 8.1, H Ar); 7.96 (2H, d,
3J = 8.5, H Ar); 8.06 (2H, d, J = 8.1, H Ar); 8.45 (1H, s, Ar-CH=); 8.48 (1H, s, Ar-CH=); 10.57 (1H, br. s,
3
OH); 10.88 (1H, br. s, OH). Mass spectrum, m/z: 421.0 [М+H]+, 419.0 [М-H]-. Found %: C 57.36; H 2.98; N
13.49. C20H12N4O4Se. Calculated, %: C 57.29; H 2.88; N 13.36.
(2E,2'E)-2,2'-(1,2,4-Selenadiazole-3,5-diyl)bis[3-(3,4-dimethoxyphenyl)acrylonitrile] (1b). Yield
1
117 mg (66%). Bright-yellow crystals; mp >250°C. Rf 0.54. IR spectrum, , cm-1: 2220 (C≡N). H NMR
3
spectrum (500 MHz), , ppm (J, Hz): 3.84 (6Н, br. s, 2OСН3); 3.88 (6Н, br. s, 2OСН3); 7.18 (1H, d, J = 8.3,
H Ar); 7.22 (1H, d, 3J = 8.2, H Ar); 7.60-7.64 (2Н, m, H Ar); 7.79-7.81 (2Н, m, H Ar); 8.49 (1H, s, Ar–CH=);
354