INTRODUCTION

Thiazole derivatives are widely studied scaffolds; they are available reagents for organic synthesis and have a wide spectrum of biological activity [1–6]. The most important representatives of this class of compounds include penicillin, nizatidine, fanetizole, meloxicam, amiphenazole, thiamine (vitamin B1) and many others [7–10] (Scheme 1).

Scheme
scheme 1

1.

Full size image

The classical approach to constructing the thiazole ring is the Hantzsch synthesis, based on the reaction of α-halocarbonyl compounds with S,N-1,3-binucleophiles (thiourea, thiocarbamates, primary thioamides) [11–14]. 2-Cyanomethylthiazoles (thiazol-2-ylacetonitriles), promising reagents for further functionalization, are easily accessible via the Hantzsch reaction involving cyanothioacetamide and various α-haloketones [15–24]. We have previously shown that bromination of (2E)-3-aryl(hetaryl)-2-[4-aryl(hetaryl)-1,3-thiazol-2-yl]acrylonitriles and (2E,4E)-5-aryl-2-(4-arylthiazol-2-yl)penta-2,4-dienenitriles in DMF occurs regioselectively at the C5 position of the thiazole ring without affecting the ethylene and diene systems to form (2E)-3-aryl-(hetaryl)-2-[5-bromo-4-aryl(hetaryl)-1,3-thiazol-2-yl]acrylonitriles [25] and (2E,4E)-5-aryl-2-(5-bromo-4-arylthiazol-2-yl)penta-2,4-diennitriles [26] (Scheme 2).

Scheme
scheme 2

2.

Full size image

In continuation of our studies in the field of obtaining functionally substituted thiazoles [27–31], 2-(4-arylthiazol-2-yl)acetonitriles 1 (Scheme 2) were chosen for studying halogenation. Compounds 1 contain two sites potentially susceptible to halogenation, namely the active methylene group CH2CN and the C5 atom of thiazole.

RESULTS AND DISCUSSION

A series of 2-(4-arylthiazol-2-yl)acetonitriles 1a–1i was prepared in yields of 67–93% by the reaction of cyanothioacetamide 2 with bromoketones 3 in methanol in the presence of triethylamine. We found that iodination of compounds 1 with an equimolar amount of crystalline iodine in DMF at 25°C leads to the formation of previously unknown 2,3-bis(4-aryl-1,3-thiazol-2-yl)but-2-enedinitriles 4a–4i in 77–93% yields (Scheme 3, method a). It is noted that the reaction is non-stereoselective, the products were formed as mixtures of E- and Z-isomers in various ratios (Scheme 3). The use of more active halogens in this reaction (chlorine or bromine) in various ratios with respect to the initial acetonitriles 1 significantly accelerates the process of their dimerization. But at the same time, the reaction is non-selective and leads to complex mixtures of products in which, in addition to the target compounds 4, halogenation products at position C5 along one or two thiazole rings were also detected. Based on the obtained results, the oxidative dimerization products 4j–4o were prepared using a simpler alternative method based on the reaction of cyanothioacetamide 2, α-bromoketone 3 and the subsequent addition of iodine in DMF at 25°C (73–89% yields, Scheme 3, method b), bypassing the synthesis, isolation and purification of nitriles 1.

Scheme
scheme 3

3.

Full size image

It should be noted that compounds 4 have not been described previously. The closest analogue, compound 5, has been prepared by electrolysis of α-phenylthio-2-benzothiazolylacetonitrile 6 in the presence of Et4NF·3HF as a minor product, along with fluorination products [32] (Scheme 4). Also, a Korean patent [33] describes the use of structurally related dicarbonitriles 7 as electroluminescent compounds.

Scheme
scheme 4

4.

Full size image

As a rule, compounds 4, unlike the starting acetonitriles 1, are poorly soluble in acetone, DMSO, DMF, chloroform or their mixtures. This fact in some cases complicates obtaining spectral characteristics and makes it impossible to separate mixtures of isomers into individual components. In the 1H and 13C NMR spectra of compounds 4a–4o, the signals have chemical shift values close to those of acetonitriles 1. At the same time, the signal of the C5 carbon atom of the thiazole fragments is slightly shifted downfield and appears in the 120.9–122.2 ppm region. The IR spectra of compounds 4a–4o contain absorption bands corresponding to the stretching vibrations of conjugated nitrile groups at 2212–2224 cm–1. The X-ray structural analysis data for substituted thiazol-2-ylacetonitrile 1i and (E)-butenedinitrile 4a are shown in Figs. 1, 2. As can be seen from Fig. 2, the structure of butenedinitrile 4a is planar, all 4 aromatic rings are in the same plane. A different picture is observed in the case of iodination of compound 1p (R = 2,4-Cl2C6H3) generated in situ from cyanothioacetamide 2 and bromoketone 3p (Scheme 5). Thus, a characteristic absorption band corresponding to the presence of a conjugated cyano group (2218 cm–1) is detected in the IR spectrum of the product. However, in the NMR spectra, in addition to the signals of aromatic substituents, two proton singlets are observed at 6.10 and 6.16 ppm, which corresponds to the presence of the ethanedinitrile fragment CH(CN)–CH(CN), and two signals of the C5H protons of thiazole at 8.25 and 8.29 ppm in equal proportions. In the 13C NMR spectrum, all carbon signals are doubled. The apparent contradiction in the IR and NMR spectra is explained as follows: the reaction product is a mixture of unsaturated dinitrile 4p (major product) and a probable transformation intermediate 2,3-bis[4-(2,4-dichlorophenyl)thiazol-2-yl]succinonitrile 8 (minor product, content in the mixture is ~5–7%). A plausible mechanism of oxidation 8→4p (Scheme 5) includes C-iodination and then dehydrohalogenation by the E1CB mechanism with the participation of the thiazole fragment as a base. The IR spectrum (ATR) corresponds to the major reaction product—unsaturated dinitrile 4p. The latter is insoluble in DMSO, unlike succinonitrile 8, therefore the NMR spectral pattern corresponds to the minor product 8. The mixture of dinitriles 4p and 8 was completely separated by boiling in acetone, with insoluble butenedinitrile 4p remaining in the precipitate, while succinonitrile 8 passes into solution. The doubling of signals in spectrum of 8 is explained by the presence of two chiral centers and the existence of product 8 as a mixture of two diastereomeric pairs—(2R,3R/2S,3S)-rac-form and the optically inactive meso-(2R,3S/2S,3R)-form (Scheme 5).

Fig. 1.
figure 1

General view of the molecule of compound 1i in the crystal.

Full size image
Fig. 2.
figure 2

General view of the molecule of compound 4a in the crystal.

Full size image
Scheme
scheme 5

5.

Full size image

In turn, each form of succinonitrile 8 can exist as several conformers. Based on the results of quantum chemical calculations, the most stable conformers were found for the (2S,3S)-enantiomer and the RS-meso-form, the structure of which is shown in Fig. 3. According to the calculated data, the SS-enantiomer has a slightly higher stability compared to the RS-meso-form, but the difference in energy between them is relatively small and is 11.8 kJ/mol in a vacuum and 5.9 kJ/mol in a DMF medium. The calculated IR spectra for the rac-form and the optically inactive meso-RS-form of succinonitrile 8 correlate quite well with the experimental spectrum, especially when using the standard correction factor [34]. The mean absolute percentage error (MAPE) in determining vibrational frequencies is 1.15 and 1.17%, respectively. The results are presented in Table 1.

Fig. 3.
figure 3

Molecular structures of the most stable conformers of the (a) rac- and (b) meso-forms of succinonitrile 8 optimized at the B3LYP-D3BJ/6-311+G(2d,p) level.

Full size image
Table 1. Comparison of experimental vibrational frequencies with quantum chemical calculation data for the most stable conformers of the rac- and meso-forms of succinonitrile 8
Full size table

CONCLUSIONS

In summary, the reaction of thiazol-2-ylacetonitriles with iodine, unlike their bromination, occurs at the cyanomethyl group and yields oxidative dimerization products—previously undescribed 2,3-bis[4-aryl-1,3-thiazol-2-yl]but-2-enedinitriles. The latter can also be obtained directly from cyanothioacetamide and bromoketones, by treating the reaction mixture with iodine in DMF. Probable dehydrodimerization intermediates are 2,3-bis(4-arylthiazol-2-yl)succinonitriles, one of which was successfully isolated as a minor product, for which the optimization of its diastereomeric forms was carried out by B3LYP-D3BJ/6-311+G(2d,p) calculation methods and their IR spectra were calculated, which showed good agreement with the experimental spectra. Structure of the key products was established using the single crystal X-ray structural analysis method. The obtained butenedinitriles are of interest as potential electroluminescent materials and possible electron-deficient substrates for organic synthesis.

EXPERIMENTAL

NMR spectra were recorded on a Bruker DPX-400 spectrometer [400.40 (1H), 100.63 MHz (13C)] in DMSO-d6 solutions. Residual solvent signals were used as a standard. IR spectra (except 4p and 8) were recorded on a Bruker Vertex 70 Fourier transform IR spectrometer by the attenuated total reflection (ATR) method on a diamond crystal in the frequency range of 400–4000 cm–1, the measurement error was ±4 cm–1. IR spectra of compounds 4p and 8 were recorded on a FT-801 Fourier transform IR spectrometer (Simex Research and Production Company, Novosibirsk) by the attenuated total reflection (ATR) method on a diamond crystal in the frequency range of 500–4000 cm–1. Elemental analysis was performed on an Elementar vario Micro cube. Individuality of the obtained samples and purity control were performed by TLC on Silufol UV254 plates, eluent—acetone–hexane (1 : 1), developer—iodine vapor, UV detector. Melting points were determined on a Kofler block and were not corrected.

General procedure for the preparation of 2-(4-arylthiazol-2-yl)acetonitriles 1a–1i. A mixture of 0.5 g (5 mmol) of cyanothioacetamide 2, 5 mmol of α-bromoketone 3a–3i and one drop of triethylamine in 15 mL of methanol was stirred until the starting components were dissolved and left for 24 h at 6°C. The resulting precipitate was filtered off, washed with cold methanol, and dried at 50°C for 3 h.

2-[4-(4-Chlorophenyl)thiazol-2-yl]acetonitrile (1а). Yield 0.927 g (79%), beige orange fine powder, mp 138–140°С. IR spectrum, ν, cm–1: 3118, 2956, 2918, 2258 (C≡N), 1905, 1645, 1496, 1461, 1396, 1317, 1294, 1197, 1155, 1105, 1081, 1056, 1010, 943, 900, 856, 835, 744, 702, 649, 526, 503, 482, 472, 412. 1Н NMR spectrum (DMSO-d6), δ, ppm: 4.64 d (2Н, СН2, 5JHH = 2.9 Hz), 7.51 d. d (1Н, НAr, 3JHH = 8.6, 4JHH = 2.7 Hz), 7.52 d. d (1Н, НAr, 3JHH = 8.6, 4JHH = 2.7 Hz), 7.96 d. d (1Н, НAr, 3JHH = 8.6, 4JHH = 2.7 Hz), 7.97 d. d (1Н, НAr, 3JHH = 8.6, 4JHH = 2.7 Hz), 8.19 d (1Н, Нthiazole, 5JHH = 2.9 Hz). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: 21.6* (СН2), 116.4 (С5Нthiazole), 117.0* (C≡N), 127.7 (2СНAr), 128.9 (2СНAr), 132.4*, 132.8* (C–Cl, C1Ar), 153.0*, 159.3* (C2thiazole, С4thiazole). Found, %: С 56.34; H 3.09; N 11.88. C11H7ClN2S (M 234.70). Calculated, %: С 56.29; H 3.01; N 11.94. *The asterisk indicates signals in antiphase.

2-[4-(4-Fluorophenyl)thiazol-2-yl]acetonitrile (1b). Yield 0.917 g (84%), beige fine powder, mp 74–75°С. IR spectrum, ν, cm–1: 3122, 3060, 2970, 2920; 2245 br, 2264 sh (C≡N), 1903, 1601, 1526, 1495, 1461, 1404, 1334, 1217, 1200, 1124, 1059, 925, 846, 802, 752, 713, 671, 622, 574, 509, 471, 422. 1Н NMR spectrum (DMSO-d6), δ, ppm: 4.63 s (2Н, СН2), 7.27 d. d. d (1Н, НAr, 3JHH = 8.8, 4JHH = 3.1, 5JHH = 2.0 Hz), 7.29 d. d. d (1Н, НAr, 3JHH = 8.9, 4JHH = 3.1, 5JHH = 2.1 Hz), 7.98 d. d. d (1Н, НAr, 3JHH = 8.9, 4JHH = 2.9, 5JHH = 2.0 Hz), 7.99 d. d. d (1Н, НAr, 3JHH = 8.8, 4JHH = 2.9, 5JHH = 2.1 Hz), 8.11 br. s (1Н, Нthiazole). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: 21.6 (СН2), 115.5* (С5Нthiazole), 115.7*, 115.9* (2СНAr), 117.1 (C≡N), 128.1*, 128.2* (2СНAr), 130.2 (C1Ar), 153.2, 159.2 (C-F), 160.9, 163.3 (C2thiazole, С4thiazole). Found, %: С 60.61; H 3.29; N 12.78. C11H7FN2S (M 218.25). Calculated, %: С 60.53; H 3.23; N 12.84.

2-[4-(3,4-Dichlorophenyl)thiazol-2-yl]acetonitrile (1с). Yield 1.103 g (82 %), beige fine powder, mp 100–102°С. IR spectrum, ν, cm–1: 3110, 2912, 2825; 2273 sh, 2248 (C≡N), 1911, 1667, 1591, 1493, 1452, 1438, 1400, 1384, 1290, 1265, 1207, 1139, 1112, 1060, 1027, 921, 875, 829, 796, 748, 676, 597, 536, 482, 433, 420. 1Н NMR spectrum (DMSO-d6), δ, ppm: 4.64 br. s (2Н, СН2), 7.71 d (1Н, НAr, 3JHH = 8.3 Hz), 7.94 d. d (1Н, НAr, 3JHH = 8.3, 4JHH = 2.0 Hz), 8.18 d (1Н, НAr, 4JHH = 2.0 Hz), 8.33 br. s (1Н, Нthiazole). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: 21.6 (СН2), 117.0 (C≡N), 117.8* (С5Нthiazole), 126.1*, 127.6* (2СНAr), 130.7 (C–Cl), 131.2* (СНAr), 131.7 (C–Cl), 134.1 (C1Ar), 151.6, 159.7 (C2thiazole, С4thiazole). Found, %: С 49.16; H 2.31; N 10.42. C11H6Cl2N2S (M 269.14). Calculated, %: С 49.09; H 2.25; N 10.41.

2-[4-(4-Methoxyphenyl)thiazol-2-yl]acetonitrile (1d). Yield 1.048 g (91%), pale yellow fine powder, mp 68–70°С. IR spectrum, ν, cm–1: 3108, 2942, 2922, 2841, 2270 (C≡N), 1909, 1608, 1531, 1471, 1438, 1413, 1321, 1274, 1249, 1172, 1155, 1112, 1054, 1027, 954, 904, 856, 836, 786, 748, 725, 651, 582, 530, 491, 464, 399. 1Н NMR spectrum (DMSO-d6), δ, ppm: 3.78 s (3H, MeO), 4.61 s (2Н, СН2), 7.00 d (2Н, HAr, 3JHH = 8.6 Hz), 7.87 d (2Н, HAr, 3JHH = 8.6 Hz), 7.96 s (1Н, Нthiazole). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: 21.6* (СН2), 55.2 (MeO), 113.5 (С5Нthiazole), 114.2 (2CHAr), 117.1* (C≡N), 126.4* (C1Ar), 127.6 (2CHAr), 154.2*, 158.7* (C2thiazole, С4thiazole), 159.3* (C4–OMe). Found, %: С 62.66; H 4.44; N 12.09. C12H10 N2O S (M 230.29). Calculated, %: С 62.59; H 4.38; N 12.16.

2-[4-(2-Oxo-2H-chromen-3-yl)thiazol-2-yl]acetonitrile (1e). Yield 1.246 g (93%), pale yellow fine powder, mp 174–176°С. IR spectrum, ν, cm–1: 3142, 2969, 2939, 2910; 2266, 2245 sh (C≡N), 1737, 1604, 1567, 1484, 1454, 1442, 1375, 1249, 1172, 1091, 1014, 950, 923, 867, 790, 754, 673, 632, 576, 460, 455, 443. 1Н NMR spectrum (DMSO-d6), δ, ppm: 4.65 s (2H, CH2), 7.38 m (1Н, Нcoumarin, 3JHH = 7.4, 3JHH = 7.6, 4JHH = 1.0 Hz), 7.44 br. d (1Н, Нcoumarin, 3JHH = 8.3 Hz), 7.63 m (1Н, Нcoumarin, 3JHH = 7.4, 3JHH = 8.3, 4JHH = 1.5 Hz), 7.93 d. d (1Н, Нcoumarin, 3JHH = 7.6, 4JHH = 1.5 Hz), 8.40 s and 8.74 s (2Н, Нthiazole, Нcoumarin). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: 21.5 (СН2), 115.9* (С5Нthiazole), 117.0 (C≡N), 119.0, 119.9 (2Сcoumarin), 121.2*, 124.8*, 129.2*, 132.2*, 139.7* (5 СНcoumarin), 147.4, 152.6, 158.8, 159.1 (2Сcoumarin, C2thiazole, С4thiazole). Found, %: С 62.71; H 3.06; N 10.49. C14H8N2O2S (M 268.03). Calculated, %: С 62.68; H 3.01; N 10.44.

2-[4-(p-Tolyl)thiazol-2-yl]acetonitrile (1f). Yield 0.718 g (67%), beige orange powder, mp 98–100°С. IR spectrum, ν, cm–1: 3139, 3107, 2935, 2916, 2260 (C≡N), 1681, 1531, 1496, 1467, 1403, 1324, 1294, 1176, 1112, 1054, 1016, 910, 858, 833, 773, 756, 688, 669, 644, 572, 528, 486, 416. 1Н NMR spectrum (DMSO-d6), δ, ppm: 2.32 s (3H, Me), 4.62 s (2H, CH2), 7.25 d (2H, HAr, 3JHH = 8.1 Hz), 7.83 d (2H, HAr, 3JHH = 8.1 Hz), 8.05 s (1Н, Нthiazole). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: 20.8 (Ме), 21.6* (СН2), 114.7 (С5Нthiazole), 117.1* (C≡N), 125.9 (2CHAr), 129.5 (2CHAr), 130.9*, 137.7* (C1Ar, C4Ar), 154.4*, 158.8* (C2thiazole, С4thiazole). Found, %: С 67.35; H 4.76; N 13.13. C12H10N2S (M 214.29). Calculated, %: С 67.26; H 4.70; N 13.07.

2-[4-(4-Bromophenyl)thiazol-2-yl]acetonitrile (1g). Yield 1.228 g (88%), beige fine powder, mp 138–140°С. IR spectrum, ν, cm–1: 3120, 2950, 2912, 2256 (C≡N), 1672, 1652, 1589, 1515, 1494, 1459, 1396, 1315, 1294, 1216, 1197, 1159, 1112, 1064, 1056, 1006, 943, 898, 856, 831, 744, 705, 651, 528, 499, 474, 418, 405. 1Н NMR spectrum (DMSO-d6), δ, ppm: 4.63 s (2H, CH2), 7.65 d (2H, HAr, 3JHH = 8.6 Hz), 7.90 d (2H, HAr, 3JHH = 8.6 Hz), 8.20 s (1Н, Нthiazole). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: 21.6* (CH2), 116.5 (С5Нthiazole), 117.1* (C≡N), 121.5* (CBr), 128.0 (2CHAr), 131.9 (2CHAr), 132.8* (C1Ar), 153.0*, 159.3* (C2thiazole, С4thiazole). Found, %: С 47.27; H 2.47; N 9.96. C11H7BrN2S (M 279.16). Calculated, %: С 47.33; H 2.53; N 10.04.

2-[4-(4-Nitrophenyl)thiazol-2-yl]acetonitrile (1h).Yield 0.969 g (79%), pale orange fine powder, mp 145–147°С. IR spectrum, ν, cm–1: 3122, 2952, 2941; 2272 пл., 2247 (C≡N), 1683, 1597, 1508, 1402, 1338, 1321, 1230, 1205, 1178, 1118, 1106, 1058, 1008, 971, 933, 856, 844, 794, 773, 746, 690, 628, 613, 551, 528, 472, 453, 408. 1Н NMR spectrum (DMSO-d6), δ, ppm: 4.67 d (2H, CH2, 5JHH = 1.7 Hz), 8.21 d. d (2H, HAr, 3JHH = 8.9, 4JHH = 1.8 Hz), 8.31 d. d (2H, HAr, 3JHH = 8.9, 4JHH = 1.8 Hz), 8.48 d (1Н, Нthiazole, 5JHH = 1.7 Hz). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: 21.6 (СН2), 116.9 (C≡N), 119.9* (С5Нthiazole), 124.3* (2CHAr), 127.0* (2CHAr), 139.5(C1Ar), 146.8, 151.9, 160.1 (С4Ar, C2thiazole, С4thiazole). Found, %: С 53.97; H 2.94; N 17.25. C11H7N3O2S (M 245.26). Calculated, %: С 53.87; H 2.88; N 17.13.

2-[4-(6-Bromo-2-oxo-2H-chromen-3-yl)thiazol-2-yl]acetonitrile (1i). Yield 1.458 g (84%), beige pink crystals, mp 217–219°С. IR spectrum, ν, cm–1: 3142, 3103, 3059, 2948, 2906; 2275 sh, 2251(C≡N), 1722 (С=О), 1600, 1560, 1504, 1475, 1348, 1367, 1263, 1243, 1216, 1176, 1126, 1083, 1068, 1008, 962, 900, 865, 815, 781, 755, 675, 651, 619, 574, 565, 507, 457, 416. 1Н NMR spectrum (DMSO-d6), δ, ppm: 4.65 d (2H, CH2, 5JHH = 1.6 Hz), 7.40 d (1Н, Нcoumarin, 3JHH = 8.8 Hz), 7.75 d. d (1Н, Нcoumarin, 3JHH = 8.8, 4JHH = 2.2 Hz), 8.22 d (1Н, Нcoumarin, 4JHH = 2.2 Hz), 8.42 d (1Н, Нthiazole, 5JHH = 1.7 Hz), 8.71 s (1Н, Нcoumarin). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: 21.5 (СН2), 116.5, 117.0 (C≡N, Сcoumarin), 118.2* (С5Нthiazole), 120.9, 121.0 (2Сcoumarin), 121.9*, 131.2*, 134.4*, 138.3* (4СНcoumarin), 147.1, 151.6, 158.3, 159.2 (C2thiazole, С4thiazole, С=О, С8аcoumarin). Found, %: С 48.49; H 2.12; N 8.15. C14H7BrN2O2S (M 347.19). Calculated, %: С 48.43; H 2.03; N 8.07.

General procedure for the preparation of 2,3-bis(4-aryl-1,3-thiazol-2-yl)but-2-enedinitriles 4a–4o. a. To a solution of 5 mmol of 2-(4-arylthiazol-2-yl)acetonitrile 1a–1i in 20 mL of DMF was added with stirring 1.269 g (5 mmol) of crystalline iodine. After 12 h, the resulting precipitate was filtered off, washed with ethanol and dried at 80°C for 3 h. Compounds 4a–4i were obtained.

b. A solution of 0.5 g (5 mmol) of cyanothioacetamide 2 and 5 mmol of the corresponding α-bromoketone 3j–3p in 20 mL of DMF was stirred for 0.5 h, then 1.269 g (5 mmol) of crystalline iodine was added until it was completely dissolved. After 12 h, the resulting precipitate was filtered off, washed with ethanol, and dried at 80°C for 3 h. Compounds 4j–4p were obtained.

In some cases, it was not possible to record the 1H and 13C NMR spectra due to the poor solubility of compounds 4 in available solvents and their mixtures, as a result of which it was not possible to establish the ratio of E- and Z-isomers for some products.

2,3-Bis[4-(4-chlorophenyl)-1,3-thiazol-2-yl]but2-enedinitrile (4a). Yield 1.012 g (87%, major : minor = 4 : 1), red fine powder, mp 293–295°С. IR spectrum, ν, cm–1: 3114, 2216 br (2C≡N), 1633, 1598, 1525, 1467, 1423, 1311, 1282, 1268, 1203, 1085, 1037, 1010, 910, 860, 833, 815, 759, 708, 671, 530, 516, 487, 478, 422. 1Н NMR spectrum (DMSO-d6), δ, ppm: major isomer, 7.60 br. d (4Н, HAr, 3JHH = 8.2 Hz), 8.08 br. d (4Н, HAr, 3JHH = 8.2 Hz), 8.75 br. s (2Н, Нthiazole); minor isomer, 7.60 br. d (4Н, HAr, 3JHH = 8.2 Hz), 8.13 br. d (4Н, HAr, 3JHH = 8.2 Hz), 8.80 br. s (2Н, Нthiazole). 13С NMR spectrum (DMSO-d6), δС, ppm: major isomer, 128.2* (4СНAr), 129.3* (4СНAr); minor isomer, 127.8* (4СНAr), 128.9* (4СНAr). Found, %: С 56.72; H 2.22; N 11.95. C22H10Cl2 N4S2 (M 465.38). Calculated, %: С 56.78; H 2.17; N 12.04.

2,3-Bis[4-(4-fluorophenyl)-1,3-thiazol-2-yl]but2-enedinitrile (4b). Yield 0.995 g (92%, major : minor = 3 : 1), orange fine powder, mp 280–282°С. IR spectrum, ν, cm–1: 3099, 2220 br (2C≡N), 1660, 1602, 1525, 1475, 1430, 1309, 1294, 1274, 1222, 1157, 1103, 1081, 1043, 1012, 962, 910, 862, 838, 806, 777, 755, 690, 669, 624, 530, 503, 437. 1Н NMR spectrum (DMSO-d6), δ, ppm: major isomer, 7.36–7.40 m (4Н, HAr), 8.16–8.17 m (4Н, HAr), 8.73 s (2Н, Нthiazole); minor isomer, 7.36–7.40 m (4Н, HAr), 8.10–8.12 m (4Н, HAr), 8.70 s (2Н, Нthiazole). Found, %: С 60.21; H 2.27; N 12.89. C22H10F2 N4S2 (M 432.47). Calculated, %: С 61.10; H 2.33; N 12.96.

2,3-Bis[4-(3,4-dichlorophenyl)-1,3-thiazol-2-yl]but-2-enedinitrile (4c). Yield 1.135 g (85%), brown fine powder, mp > 300°С (decomp.). IR spectrum, ν, cm–1: 3111 br, 2220 (2C≡N), 1672, 1596, 1560, 1467, 1427, 1392, 1294, 1272, 1203, 1136, 1084, 1027, 925, 896, 870, 816, 766, 712, 675, 551, 532, 523, 455, 435, 424, 395. Found, %: С 49.51; H 1.64; N 10.54. C22H8Cl4 N4S2 (M 534.27). Calculated, %: С 49.46; H 1.51; N 10.49.

2,3-Bis[4-(4-methoxyphenyl)-1,3-thiazol-2-yl]but-2-enedinitrile (4d). Yield 1.039 g (91%, major : minor = 10 : 1), red fine powder, mp > 270°С (decomp.). IR spectrum, ν, cm–1: 3110, 2958, 2836, 2214 (2C≡N), 1608, 1529, 1466, 1434, 1303, 1249, 1174, 1112, 1974, 1025, 939, 910, 860, 831, 809, 773, 754, 707, 690, 671, 584, 513, 414. 1Н NMR spectrum (DMSO-d6), δ, ppm: major isomer, 3.80 br. s (6Н, МеО), 7.03 br. d (4Н, HAr, 3JHH = 8.8 Hz), 7.97 d (4Н, HAr, 3JHH = 8.8 Hz), 8.54 s (2Н, Нthiazole); minor isomer, 3.80 br. s (6Н, МеО), 7.03 br. d (4Н, HAr, 3JHH = 8.8 Hz), 7.88 d (4Н, HAr, 3JHH = 8.8 Hz), 8.52 s (2Н, Нthiazole). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: major isomer, 55.3 (4МеО), 114.4 (4СНAr), 116.5*, 117.1* (C=C, 2C≡N), 121.0 (2C5Hthiazole), 125.3* (2С1Ar), 127.9 (4СНAr), 156.4*, 156.7*, 160.0* (2C2thiazole, 2С4thiazole, 2C4Ar). Found, %: С 63.24; H 3.59; N 12.34. C24H16 N4O2S2 (M 456.54). Calculated, %: С 63.14; H 3.53; N 12.27.

2,3-Bis[4-(2-oxo-2H-chromen-3-yl)-1,3-thiazol-2-yl]but-2-enedinitrile (4e). Yield 1.025 g (77%), dark red fine powder, mp > 300°С (decomp.). IR spectrum, ν, cm–1: 3138, 2218 (2C≡N), 1741, 1722 (2C=O), 1606, 1567, 1479, 1461, 1444, 1376, 1290, 1274, 1257, 1176, 1122, 1087, 1068, 1000, 956, 923, 867, 786, 752, 707, 673, 630, 580, 489, 455, 412. Found, %: С 63.24; H 2.33; N 10.63. C28H12N4O4S2 (M 532.55). Calculated, %: С 63.15; H 2.27; N 10.52.

2,3-Bis[4-(4-methylphenyl)-1,3-thiazol-2-yl]but-2enedinitrile (4f). Yield 0.913 g (86%, major : minor = 5 : 3), dark red powder, mp > 300°С (decomp.). IR spectrum, ν, cm–1: 3097, 3060, 2915, 2217 (2C≡N), 1670, 1610, 1573, 1475, 1436, 1321, 1292, 1270, 1240, 1184, 1114, 1079, 1041, 1018, 952, 908, 860, 819, 784, 755, 705, 671, 574, 528, 487, 426. 1Н NMR spectrum (DMSO-d6), δ, ppm: major isomer, 2.36 br. s (6Н, Ме), 7.33 br. d (4Н, НAr, 3JHH = 7.9 Hz), 8.01 d (4Н, НAr, 3JHH = 7.9 Hz), 8.67 s (2Н, Нthiazole); minor isomer, 2.36 br. s (6Н, Ме), 7.33 br. d (4Н, НAr, 3JHH = 7.9 Hz), 7.95 d (4Н, НAr, 3JHH = 7.9 Hz), 8.65 s (2Н, Нthiazole). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: major isomer, 20.9* (2Me), 115.9, 116.4, 117.7 (C=C, 2C≡N), 122.0* (2C5Hthiazole), 126.4* (4СНAr), 129.7* (4СНAr), 129.7, 138.8 (2С1Ar, 2C4Ar), 156.7, 158.1 (2C2thiazole, 2С4thiazole); minor isomer, 20.8* (2Me), 115.9, 116.4, 117.8 (C=C, 2C≡N), 120.9* (2C5Hthiazole), 126.0* (4СНAr), 129.5* (4СНAr), 130.2, 139.1 (2С1Ar, 2C4Ar), 156.3, 157.6 (2C2thiazole, 2С4thiazole). Found, %: С 67.85; H 3.53; N 13.11. C24H16 N4S2 (M 424.54). Calculated, %: С 67.90; H 3.80; N 13.20.

2,3-Bis[4-(4-bromophenyl)-1,3-thiazol-2-yl]but-2enedinitrile (4g). Yield 1.247 g (90%, major : minor = 4 : 1), orange powder, mp 308–310°С (decomp.). IR spectrum, ν, cm–1: 3110, 2212 (2C≡N), 1592, 1523, 1467, 1434, 1421, 1309, 1282, 1270, 1243, 1203, 1180, 1106, 1066, 1035, 1006, 966, 944, 910, 862, 831, 815, 782, 757, 705, 665, 626, 530, 516, 484, 418. 1Н NMR spectrum (DMSO-d6), δ, ppm: major isomer, 7.75 d (4Н, НAr, 3JHH = 8.6 Hz), 8.06 d (4Н, НAr, 3JHH = 8.6 Hz), 8.81 s (2Н, Нthiazole); minor isomer, 7.71 d (4Н, НAr, 3JHH = 8.6 Hz), 8.01 d (4Н, НAr, 3JHH = 8.6 Hz), 8.76 s (2Н, Нthiazole). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: 116.3, 118.1 (C=C, 2C≡N), 122.6 (2CBr), 123.5* (2C5Hthiazole), 128.5* (4СНAr), 131.8 (2С1Ar), 132.2* (4СНAr), 155.2, 156.8 (2C2thiazole, 2С4thiazole). Found, %: С 47.75; H 1.94; N 10.18. C22H10Br2N4S2 (M 554.28). Calculated, %: С 47.67; H 1.82; N 10.11.

2,3-Bis[4-(4-nitrophenyl)-1,3-thiazol-2-yl]but-2-enedinitrile (4h). Yield 1.131 g (93%), dark yellow powder, mp > 300°С (decomp.). IR spectrum, ν, cm–1: 3118, 3093, 2224 (2C≡N), 1666, 1599, 1508, 1434, 1340, 1313, 1272, 1241, 1214, 1108, 1081, 1043, 1010, 912, 865, 844, 784, 744, 696, 667, 628, 528, 509, 466, 416. Found, %: С 54.39; H 2.10; N 17.25. C22H10N6O4S2 (M 486.49). Calculated, %: С 54.32; H 2.07; N 17.28.

2,3-Bis[4-(6-bromo-2-oxo-2H-chromen-3-yl)-1,3-thiazol-2-yl]but-2-enedinitrile (4i). Yield 1.363 g (79%), dark red powder, mp > 300°С (decomp.). IR spectrum, ν, cm–1: 3126, 2220 (2C≡N), 1724 (2C=O), 1668, 1600, 1562, 1477, 1456, 1402, 1365, 1288, 1245, 1211, 1184, 1137, 1097, 1066, 1018, 1008, 946, 904, 873, 819, 794, 746, 705, 653, 622, 586, 561, 513, 491, 453, 414. Found, %: С 48.89; H 1.53; N 8.15. C28H10Br2N4O4S2 (M 690.34). Calculated, %: С 48.71; H 1.46; N 8.12.

2,3-Bis[4-(3,4-dimethylphenyl)-1,3-thiazol-2-yl]but-2-enedinitrile (4j). Yield 0.95 g (84%, major : minor = 7 : 1), red powder, mp > 300°С (decomp.). IR spectrum, ν, cm–1: 3116, 2966, 2941, 2917, 2856, 2216 (2C≡N), 1610, 1571, 1531, 1475, 1398, 1382, 1299, 1270, 1166, 1128, 1103, 1078, 1049, 1024, 997, 943, 908, 883, 836, 821, 754, 705, 690, 607, 549, 528, 455, 436. 1Н NMR spectrum (DMSO-d6), δ, ppm: major isomer, 2.27 br. s (6Н, Ме), 2.29 br. s (6Н, Ме), 7.27 br. d (2Н, НAr, 3JHH = 7.8 Hz), 7.77 br. d (2Н, НAr, 3JHH = 7.8 Hz), 7.82 br. s (2Н. НAr), 8.64 br. s (2Н, Нthiazole); minor isomer, 2.27 br. s (6Н, Ме), 2.29 br. s (6Н, Ме), 7.27 br. d (2Н, НAr, 3JHH = 7.8 Hz), 7.72 br. d (2Н, НAr, 3JHH = 7.8 Hz), 7.84 br. s (2Н, НAr), 8.63 br. s (2Н, Нthiazole). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: 19.3* (2Me), 19.6* (2Me), 116.4, 117.7 (C=C, 2C≡N), 121.8* (2C5Hthiazole), 124.0* (2СНAr), 127.4* (2СНAr), 130.2* (2СНAr), 130.3 (2С1Ar), 137.0 (2CMe), 137.6 (2CMe), 156.4, 156.9 (2C2thiazole, 2С4thiazole). Found, %: С 69.10; H 4.53; N 12.42. C26H20N4S2 (M 452.59). Calculated, %: С 69.00; H 4.45; N 12.38.

2,3-Bis[4-(3,4-dimethylphenyl)-1,3-thiazol-2-yl]but-2-enedinitrile (4k). Yield 0.783 g (79%, major : minor = 2 : 1), orange powder, mp 238–240°С. IR spectrum, ν, cm–1: 3103, 2216 (2C≡N), 1580, 1510, 1479, 1432, 1324, 1292, 1274, 1241, 1207, 1180, 1159, 1101, 1083, 1041, 1052, 1000, 919, 908, 858, 777, 728, 688, 671, 635, 528, 516, 472, 415. 1Н NMR spectrum (DMSO-d6), δ, ppm: major isomer, 7.50–7.54 m (6Н, НAr), 8.06 br. d (4Н, НAr, 3JHH = 7.3 Hz), 8.73 br. s (2Н, Нthiazole); minor isomer, 7.42–7.46 m (6Н, НAr), 8.12 br. d (4Н, НAr, 3JHH = 7.3 Hz), 8.74 br. s (2Н, Нthiazole). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: major isomer, 116.8, 118.3 (C=C, 2C≡N), 123.3* (2C5Hthiazole), 126.9* (4СНAr), 129.6* (4СНAr), 129.7* (2СНAr), 133.1 (2С1Ar), 156.9, 157.1 (2C2thiazole, 2С4thiazole); minor isomer, 114.1, 116.4 (C=C, 2C≡N), 122.1* (2C5Hthiazole), 126.9* (4СНAr), 129.6* (4СНAr), 129.7* (2СНAr), 133.3 (2С1Ar), 157.3, 158.6 (2C2thiazole, 2С4thiazole). Found, %: С 66.56; H 3.02; N 14.11. C22H12N4S2 (M 396.49). Calculated, %: С 66.64; H 3.05; N 14.13.

2,3-Bis[4-isobutylphenyl-1,3-thiazol-2-yl]but-2enedinitrile (4l). Yield 0.992 g (78%, major : minor = 3 : 1), orange powder, mp 270–272°С. IR spectrum, ν, cm–1: 312, 2950, 2923, 2896, 2863, 2220 (2C≡N), 1610, 1537, 1466, 1438, 1363, 1319, 1303, 1274, 1240, 1184, 1164, 1120, 1081, 1018, 941, 910, 856, 798, 773, 748, 719, 703, 673, 619, 532, 513, 424. 1Н NMR spectrum (DMSO-d6), δ, ppm: major isomer, 0.88 br. d (12Н, Ме, 3JHH = 6.6 Hz), 1.87 m (2Н, СН), 2.49–2.53 m (4Н, СН2, partial overlapping with DMSO signal), 7.31 d (4Н, НAr, 3JHH = 8.3 Hz), 8.02 d (4Н, НAr, 3JHH = 8.3 Hz), 8.67 s (2Н, Нthiazole); minor signal, 0.88 br. d (12Н, Ме, 3JHH = 6.6 Hz), 1.87 m (2Н, СН), 2.49–2.53 m (4Н, СН2, partial overlapping with DMSO signal), 7.30 d (4Н, НAr, 3JHH = 8.3 Hz), 8.96 d (4Н, НAr, 3JHH = 8.3 Hz), 8.66 s (2Н, Нthiazole). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: major isomer, 22.2* (4Ме), 29.6* (2СН), 44.3 (2СН2), 115.9, 117.7 (C=C, 2C≡N), 121.0* (2C5Hthiazole), 126.4* (4СНAr), 129.7* (4СНAr), 130.5 (2С1Ar), 142.5 (2С4Ar), 156.6, 156.8 (2C2thiazole, 2С4thiazole); minor isomer, 22.2* (4Ме), 29.6* (2СН), 44.3 (2СН2), 116.4, 117.7 (C=C, 2C≡N), 122.2* (2C5Hthiazole), 126.3* (4СНAr), 129.7* (4СНAr), 130.3 (2С1Ar), 142.3 (2С4Ar), 156.5, 156.7 (2C2thiazole, 2С4thiazole). Found, %: С 70.79; H 5.49; N 11.06. C30H28N4S2 (M 508.70). Calculated, %: С 70.83; H 5.55; N 11.01.

2,3-Bis[4-(3,4-dimethoxyphenyl)-1,3-thiazol-2-yl]but-2-enedinitrile (4m). Yield 1.137 g (88%, major : minor = 1 : 1), purple powder, mp > 300°С (decomp.). IR spectrum, ν, cm–1: 3106, 2993, 2962, 2945, 2833, 2212 (2C≡N), 1670, 1602, 1587, 1527, 1486, 1469, 1432, 1403, 1342, 1301, 1272, 1261, 1236, 1205, 1162, 1141, 1078, 1051, 1022, 962, 946, 881, 802, 750, 727, 707, 690, 605, 578, 514, 505, 420, 397. 1Н NMR spectrum (DMSO-d6), δ, ppm: major isomer, 3.77–3.86 m (12Н, МеО), 7.06–7.14 m (2Н, НAr), 7.23 br. s (2Н, НAr), 7.61–7.79 m (2Н, НAr), 8.66 br. s (2Н, Нthiazole); minor isomer, 3.77–3.86 m (12Н, МеО), 7.06–7.14 m (2Н, НAr), 7.22 br. s (2Н, НAr), 7.61–7.79 m (2Н, НAr), 8.61 br. s (2Н, Нthiazole). Found, %: С 60.48; H 3.97; N 10.88. C26H20N4О4S2 (M 516.59). Calculated, %: С 60.45; H 3.90; N 10.85.

2,3-Bis[4-(3-methoxyphenyl)-1,3-thiazol-2-yl]but-2-enedinitrile (4n). Yield 0.845 g (74%, major : minor = 5 : 2), dark red powder, mp 240–242°С. IR spectrum, ν, cm–1: 3110, 3089, 3000, 2939, 2833, 2216 (2C≡N), 1598, 1581, 1508, 1483, 1461, 1432, 1419, 1309, 1274, 1240, 1170, 1160, 1108, 1079, 1039, 995, 939, 877, 867, 792, 754, 709, 692, 682, 609, 563, 522, 511, 486, 451, 416. 1Н NMR spectrum (DMSO-d6), δ, ppm: major isomer, 3.80–3.85 m (6Н, МеО), 7.96–7.02 m (2Н, НAr), 7.40–7.44 m (2Н, НAr), 7.60–7.67 m (4Н, НAr), 8.77 br. s (2Н, Нthiazole); minor isomer, 3.80–3.85 m (6Н, МеО), 7.96–7.02 m (2Н, НAr), 7.40–7.44 m (2Н, НAr), 7.60–7.67 m (4Н, НAr), 8.75 br. s (2Н, Нthiazole). Found, %: С 63.21; H 3.62; N 12.33. C24H16N4О2S2 (M 456.54). Calculated, %: С 63.14; H 3.53; N 12.27.

2,3-Bis[4-(2,4-dimethylphenyl)-1,3-thiazol-2-yl]but-2-enedinitrile (4о). Yield 1.007 g (89%, major : minor = 2 : 1), orange powder, mp 279–281°С. IR spectrum, ν, cm–1: 3155, 2976, 2916, 2862, 2214 (2C≡N), 1674, 1610, 1479, 1438, 1394, 1377, 1301, 1263, 1245, 1199, 1168, 1078, 1033, 1008, 939, 904, 871, 848, 829, 752, 717, 711, 692, 673, 599, 570, 543, 518, 566, 446, 422, 393. 1Н NMR spectrum (DMSO-d6), δ, ppm: major isomer, 2.32 br. s (6Н, Ме), 2.40 br. s (6Н, Ме), 7.13 br. d (2Н, НAr, 3JHH = 7.9 Hz), 7.17 br. s (2Н, НAr), 7.56 br. s (2Н, НAr, 3JHH = 7.9 Hz), 8.33 br. s (2Н, Нthiazole); minor isomer, 2.32 br. s (6Н, Ме), 2.40 br. s (6Н, Ме), 7.13 br. d (2Н, НAr, 3JHH = 7.9 Hz), 7.21 br. s (2Н, НAr), 7.63 br. s (2Н, НAr, 3JHH = 7.9 Hz), 8.38 br. s (2Н, Нthiazole). Found, %: С 68.89; H 4.41; N 12.30. C26H20N4S2 (M 452.60). Calculated, %: С 69.00; H 4.45; N 12.38.

2,3-Bis[4-(2,4-dichlorophenyl)-1,3-thiazol-2-yl]but-2-enedinitrile (4p). Yield 0.975 g (73%). Crude sample is brown, after boiling in acetone the sample is yellow powder, mp > 300°С (decomp.). IR spectrum, ν, cm–1: 3153, 3095, 2218 (2C≡N), 1661, 1589, 1552, 1493, 1471, 1427, 1371, 1295, 1253, 1191, 1114, 1106, 1085, 1060, 1037, 1025, 1008, 914, 865, 829, 794, 767, 715, 686, 667, 551, 541, 499, 459, 447, 403. Found, %: С 49.51; H 1.54; N 10.52. C22H8Cl4N4S2 (M 534.27). Calculated, %: С 49.46; H 1.51; N 10.49.

2,3-Bis[4-(2,4-dichlorophenyl)thiazol-2-yl]succinonitrile (8). A mixture of (2R,2R/2S,2S)- and (2R,3S/2S,3R)-diastereomers. The sample was obtained by boiling the crude product 4p in acetone and then evaporating the filtrate. Brown powder, mp 230–232°С. IR spectrum, ν, cm–1: 3154, 3139, 3083, 2921, 1588, 1553, 1507, 1487, 1453, 1431, 1372, 1295, 1242, 1194, 1142, 1105, 1086, 1080, 1036, 916, 868, 859, 830, 779, 764, 720, 698, 689, 673, 656, 642, 556, 531, 517. 1Н NMR spectrum (DMSO-d6), δ, ppm: 6.12 s (1Н, СНC≡N), 6.18 s (1Н, СН≡CN), 7.54–7.60 m (2Н, НAr), 7.77–7.93 m (4H, НAr), 8.27 s (1Н, C5Hthiazole), 8.31 s (1Н, C5Hthiazole). 13С DEPTQ NMR spectrum (DMSO-d6), δС, ppm: 37.6*, 37.9* (2 CHC≡N), 116.2, 116.3 (2C≡N), 122.59*, 122.64* (2CHAr), 127.7*, 127.8* (2CHAr), 129.91*, 129.93* (2CHAr), 131.00, 131.02 (2C–Cl), 131.9 (2C–Cl), 132.56*, 132.63* (2 C5Hthiazole), 133.67, 133.69 (2C1Ar), 149.7, 149.8 (2C4thiazole), 158.0, 158.3 (2C2thiazole).

Single crystal X-ray diffraction analysis was performed on an Agilent Super Nova, Dual, Cu at zero, Atlas S2 automatic four-circle diffractometer at 100.01(11) K. The structure was solved by the direct method in the Olex2 [35] and ShelXD [36] software package and refined using the SHELXL package [37]. The structure was refined by the full-matrix least squares method in the anisotropic approximation for non-hydrogen atoms by F2.

The main characteristics of the experiment and the unit cell parameters of 2-[4-(6-bromo-2-oxo-2H-chromen-3-yl)thiazol-2-yl]acetonitrile 1i (C14H7BrN2O2S): crystal size 0.438 × 0.188 × 0.14 mm, monoclinic crystal system, space group P21/c, M = 347.19, a = 14.65521(13) Å, b = 4.62521(4) Å, c = 18.97709(16) Å, α = 90°, β = 98.9748(8)°, γ = 90°, V = 1270.582(19) Å3, Z = 4, dcalc = 1.815 g/cm3; μ(CuKα λ = 1.54184) = 5.977 mm–1, F(000) = 688.0, 2θ = 9.436–152.646°; reflection index intervals: –18 ≤ h ≤ 18, –4 ≤ k ≤ 5, –23 ≤ l ≤ 23; number of measured reflections is 19077, number of independent reflections is 2661 (Rint = 0.0256, Rsigma = 0.0117), number of reflections with I > 2σ(I) is 2661, number of refined parameters is 182; R-factor [I > 2σ(I)]: R1 = 0.0236 (wR2 = 0.0637); R-factor for all reflections: R1 = 0.0238 (wR2 = 0.0639), GOOF by F2 is 1.078; Δρmax/Δρmin = 0.88/–0.50 е/Å3. The X-ray diffraction results were deposited in the Cambridge Structural Data Bank (CCDC 2358395).

The main characteristics of the experiment and the unit cell parameters of (E)-2,3-bis[4-(4-chlorophenyl)-1,3-thiazol-2-yl]but-2-enedicarbonitrile 4a (C22H10Cl2N4S2): crystal size 0.288 × 0.089 × 0.058 mm, triclinic crystal system, space group P-1, M = 465.36, a = 4.9649(2) Å, b = 8.5460(3) Å, c = 11.9953(4) Å, α = 104.826(3)°, β = 94.452(4)°, γ = 90.409(4)°, V = 490.34(3) Å3, Z = 1, dcalc = 1.576 g/cm3; μ(CuKα λ = 1.54184) = 5.118 mm–1, F(000) = 236.0, 2θ = 7.65–153.06°; reflection index intervals: –5 ≤ h ≤ 6, –10 ≤ k ≤ 10, –15 ≤ l ≤ 15; number of measured reflections is 14147, number of independent reflections is 2051 (Rint = 0.0400, Rsigma = 0.0195), number of reflections with I > 2σ(I) is 2051, number of refined parameters is 136; R-factor [I > 2σ(I)]: R1 = 0.0289 (wR2 = 0.0777), R-factor for all reflections: R1 = 0.0301 (wR2 = 0.0789), GOOF by F2 is 1.068; Δρmax/Δρmin = 0.38/–0.34 е/Å3. The X-ray diffraction results were deposited in the Cambridge Structural Data Bank (CCDC 2358400).

Quantum chemical calculations of the molecular geometry and vibrational spectra of various isomers of succinonitrile 8 were performed in the ORCA 5.0.4 software package [38, 39] using the B3LYP hybrid DFT functional [40, 41] with the D3BJ dispersion correction [42] in the 6-311+G(2d,p) valence-split basis set. Comparison of the calculated vibrational frequencies with the experimental ones was performed taking into account the correction coefficient {0.9679 for high-frequency (>1000 cm−1) and 1.0100 for low-frequency vibrations (<1000 cm−1) [34]}. To calculate the energy of various isomers in the DMF medium, the conductive continuum model (CPCM) was used [43]. The calculation of vibrational frequencies was carried out after a preliminary search for the most stable conformations with subsequent optimization of the molecular geometry. Gabedit 2.5 [44] was used to generate Input files. ChemCraft 1.8 [45] was used to visualize the molecular geometry and vibrational frequencies.