In the field of search and synthesis of new bioactive molecules, the chemistry of heterocyclic compounds plays an important role. Compounds having five-membered nitrogen- and oxygen-containing heterocycles, such as triazole [1–4], indazole [5–9], and benzisoxazole [10–12], have a wide range of biological activity. A number of compounds containing a triazole [13], indazole [14], or benzisoxazole [15] structural fragment are used in many modern drugs, including antitumor, antiviral, anti-inflammatory, antibacterial, and other pharmaceuticals. Some drugs are at the stage of clinical trials, such as the antitumor drug SNX-5422, the pharmaceutical substance of which contains a derivative of tetrahydroindazolone [16]. The 1,2,3-triazole cycle is often used to create new hybrid molecules with an increased therapeutic potential [17, 18]. This heterocyclic system can serve not only as a linker for combining pharmacophore fragments, but also acts as a pharmacophore itself. Thus, the combination of indazolone and triazole or benzisoxazolone and triazole fragments into a single hybrid molecule can lead to compounds with high biological activity. Triazole-containing 1,5,6,7-tetrahydro-4H-indazol-4-ones and 6,7-dihydrobenzo[d]isoxazol-4(5H)-ones are not described in the literature.

The aim of this work is the synthesis of triazole-containing 1,5,6,7-tetrahydro-4H-indazol-4-ones and 6,7-dihydrobenzo[d]isoxazol-4(5H)-ones.

At present, a number of strategies have been developed for the synthesis of indazoles [19], benzisoxazoles [20], and their derivatives. Due to the presence of three electrophilic centers (one exo-cyclic and two endo-cyclic carbonyl groups) and high reactivity, cyclic triacylmethanes can be used to construct various heterocyclic structures [21]. It is known that 2-acylcyclohexane-1,3-diones interact with N,N- and N,O-dinucleophiles to give the corresponding indazolones and benzisoxazolones [22]. To synthesize new derivatives of tetrahydroindazolones and dihydrobenzisoxazolones containing a triazole fragment, we used 2-[(1H-1,2,3-triazol-1-yl)acetyl]cyclohexane-1,3-diones as block synthons (Scheme 1).

Scheme
scheme 1

1.

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By C-acylation of cyclohexane-1,3-diones 1a, 1b with triazolylacetic acids 2a, 2b according to the procedure proposed by us earlier for the preparation of 2-(tetrazolylacetyl)cyclohexane-1,3-diones [23], we obtained 2-acylcyclohexane-1,3-diones 3а–3d containing a triazole ring in the side acyl chain in 75–80% yield. Reaction of 2-[(1H-1,2,3-triazol-1-yl)acetyl]cyclohexane-1,3-diones 3а–3d with a small excess of an equimolar mixture of phenylhydrazine hydrochloride or 4-fluorophenylhydrazine and sodium hydroxide in ethanol for 48 h at room temperature led in high yield (71–87%) to the heterocyclization products of intermediate hydrazones, indazolones 4a–4h. Cyclocondensation of 2-[(1H-1,2,3-triazol-1-yl)acetyl]cyclohexane-1,3-diones 3a–3d with hydroxylamine was used to obtain 6,7-dihydrobenzisoxazolones 5а–5d. Treatment of triketones 3а–3d with an equimolar mixture of hydroxylamine hydrochloride and sodium hydroxide for 8 h at room temperature in ethanol gave the target benzisoxazolones 5а–5d in 61–81% yield.

The structure and composition of synthesized compounds 3a–3d, 4a–4h, 5а–5d were confirmed by 1Н, 13С, 19F NMR spectroscopy and elemental analysis data. In the 1H NMR spectra of triketones 3a–3d, along with the signals of the hydrogen atoms of CH2 and CH3 groups, there are a proton signal at the carbon atom of the triazole ring in the form of a singlet in the range of 7.29– 7.81 ppm and a signal of the enol proton in the form of a broadened singlet in the downfield region of order 16.41–16.45 ppm, which indicates the tricarbonyl system enolization and a strong hydrogen bond. In the 13С NMR spectra of compounds 3а–3d, in the region of 195.6– 197.5 ppm, there are signals of carbon atoms of carbonyl groups. The carbon signal of the carbonyl group of the cycle appears in the region of 195.6–195.8 ppm (С1), the signal of the carbon of the enolized carbonyl group, in the region of 195.6–196.7 ppm (С3), and the signal of the carbonyl group of the acyl chain С1′, in the region of 196.6–197.5 ppm (С1′). The results are consistent with the data obtained earlier for related triketone systems [23, 24]. To further confirm the structure of the synthesized triketones 3а–3d, two-dimensional 1H, 13C, and 15N NMR spectra were recorded for 2-[2-(4-phenyl-1H-1,2,3-triazol-1-yl)acetyl]cyclohexane-1,3-dione 3а (Scheme 2).

Scheme
scheme 2

2.

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Thus, in the HMBC spectra, the exo-cyclic carbonyl group has a cross peak with methylene protons located outside the ring, the C3 nucleus of the enolized carbonyl group interacts with the hydroxyl proton and protons at C4, and the C1 nucleus, in turn, gives a signal with protons at the atom C6. It can be concluded that enolization is observed for the carbonyl group located in the cyclic molecule part, i.e. triketone 3a is in the form B. The assignment of the signals of nitrogen nuclei of the triazole ring is based on the observation of the interaction of the N3′′ nucleus (351.0 ppm) with the ortho-protons of the aromatic ring, the N1′′ (239.6 ppm) and N2′′ (368.6 ppm) nuclei give cross peaks with the protons of the CH2 group and the proton at the C5′′ atom, it is interesting that the N3′′ nucleus does not show a cross peak with the proton at the C5′′ atom. The establishment of differences between the nuclei N1′′ and N2′′ is based on the magnitude of the chemical shift: the nitrogen nucleus at the double bond is located in a weaker field.

The proton signal of the triazole fragment of indazolones 4a–4h and benzisoxazolones 5а–5d in the 1H NMR spectra appears as a singlet in the region of 7.57–8.18 ppm, while the signal of the protons of the methylene group at the С1′ atom appears in the region of 5.75–5.89 ppm. In the 13C NMR spectra of indazolones 4а–4h, the signal of the carbon atom of the carbonyl group (С4) and the signals of the carbon atoms of the C–N (C7a) and C=N (C3) groups are observed in the ranges of 193.2–194.0, 149.7–150.7, and 147.8– 148.4 ppm respectively, while the 13C NMR spectra of benzisoxazolones 5а–5d show signals at 192.2– 193.0 (C4), 181.8–182.4 (C7a), and 155.0–155.3 ppm (C3). According to the obtained spectroscopic data, the cyclocondensation of 2-[(1H-1,2,3-triazol-1-yl)acetyl]cyclohexane-1,3-diones 3а–3d with phenylhydrazines or hydroxylamine proceeded at the most electrophilic exo-cyclic carbonyl group, as was established for other cyclic β-triketones [25–28].

The cytotoxic activity of triazole-containing tetrahydroindazolones 4c, 4d and 6,7-dihydrobenzisoxazolones 5b, 5c was assessed in vitro against human hepatocellular carcinoma HepG2, human mammary adenocarcinoma MCF-7, and human laryngeal carcinoma Hep2 using fluorescence microscopy on an IN Cell Analyzer 2200 device (GE Healthcare, UK).

The test compounds did not show pronounced cytotoxic activity against human tumor cells HepG2, MCF-7, and Hep2 in the concentration range of 1–100 µM (IC50 > 100 µM). Slight cell death (13% apoptotic cells and 7% dead cells) was observed at the effect of compound 4c on MCF-7 cells. Compounds 4c, 4d, 5b, 5c showed moderate cytostatic properties (a decrease in the rate of cell division and, as a result, a decrease in the total number of cells compared to the control) at concentrations of 25, 50, and 100 μM (Fig. 1).

Fig. 1.
figure 1

Cytotoxic effect of compounds 4c (a, b, c), 4d (d, e, f), 5b (g, h, i), 5c (j, k, l) in relation to cell lines HepG2, MCF-7, and Hep2 after 48 h of exposure (data from three independent experiments).

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Thus, previously unknown triazole-containing 1,5,6,7-tetrahydro-4Н-indazol-4-ones and 6,7-dihydrobenzo[d]isoxazol-4(5H)-ones were synthesized starting from 2-[(1Н-1,2,3-triazol-1-yl)acetyl]cyclohexane-1,3-diones. The structure and composition of the obtained compounds were confirmed by spectral methods. The results of bioassays showed the promise of further search for compounds with cytostatic activity in this heterocycles series.

EXPERIMENTAL

1Н, 19F, 13С, 15N NMR spectra were recorded on a Bruker-Biospin AVANCE 500 spectrometer with operating frequencies of 500.13, 470.59, 125.77, 50.70 MHz for 1Н, 19F, 13С, 15N nuclei, respectively, using a 5 mm sensor (BBO) with Z-gradient. The spectra were registered at a sample temperature of 293 K for solutions in CDCl3. The residual signal of the solvent was used as an internal standard for the 1Н and 13С NMR spectra, and the signal of nitromethane was used as an internal standard for the 15N NMR spectra. The signal of α,α,α-trifluorotoluene was used as an external standard for 19F NMR spectra. Correlation spectra (HSQC, COSY, HMBC, NOESY) were recorded and processed using standard Bruker Biospin software. Melting points were determined on a Boetius block. Elemental analysis was performed on a Eurovector EA3000 CHNS-O analyzer. The reactions progress and the products purity were monitored by TLC on Silufol UV-254 plates (ethyl acetate–petroleum ether). Column chromatography was performed on silica gel (70–230 mesh) eluting with ethyl acetate–petroleum ether.

Triazolylacetic acids 2a, 2b. To a solution of 17.1 mmol (1.97 g) of methyl-2-azidoacetate in a mixture of 50 mL of tert-butanol and 50 mL of water was added 18.9 mmol (1.92 g) of phenylacetylene [or 18.9 mmol (1.82 g) of hept-1-yne] and then 23.6 mmol (0.64 g) copper sulfate pentahydrate (0.64 g) and 23.6 mmol (1.5 g) copper powder. The reaction mixture was stirred for 20 h. The precipitate was filtered off; the filtrate was evaporated under reduced pressure to half the original volume and was extracted with ethyl acetate (3×50 mL). The combined organic layer was dried over anhydrous Na2SO4, the solvent was removed. Column chromatography of the residue gave methyl 2-(4-phenyl-1H-1,2,3-triazol-1-yl)acetate or methyl 2-(4-pentyl-1H-1,2,3-triazol-1-yl)acetate as an oil in 93% and 85% yield, respectively.

To a solution of 16.0 mmol of the resulting methyl 2-(4-phenyl-1H-1,2,3-triazol-1-yl)acetate or methyl 2-(4-pentyl-1H-1,2,3-triazolyl)acetate in a mixture of 50 mL of methanol and 50 mL of water was added 16 mmol (6.4 g) of sodium hydroxide. The reaction mixture was stirred for 24 h, methanol was removed, and the residue was acidified with 20% hydrochloric acid to pH 1. To isolate triazolylacetic acid 2а, the formed precipitate was filtered off, washed with water, and dried in air to give 2-(4-phenyl-1H-1,2,3-triazol-1-yl)acetic acid 2а in 93% yield as colorless crystals (mp 198–200°С). To isolate triazolylacetic acid 2b, the formed precipitate was filtered off, washed with water, and dried in air to give 1.99 g (63%) of acid 2b. The aqueous layer was extracted with ethyl acetate (3×30 mL), the combined organic layer was dried over anhydrous Na2SO4. After the solvent removing, 0.98 g (31%) of acid 2b was additionally obtained. The total yield of 2-(4-pentyl-1H-1,2,3-triazol-1-yl)acetic acid (2b) was 2.97 g (94%) as colorless crystals (mp 124–125°С). The physicochemical characteristics of triazolylacetic acids 2a, 2b coincide with the literature data [29, 30]. 2-[(1Н-1,2,3-Triazol-1-yl)acetyl]cyclohexane-1,3-diones 3а–3d were synthesized by analogy with the procedure described in [23].

2-[2-(4-Phenyl-1Н-1,2,3-triazol-1-yl)acetyl]cyclohexan-1,3-dione (3a) was obtained from cyclohexane-1,3-dione 1a and 2-(4-phenyl-1H-1,2,3-triazol-1-yl)acetic acid 2a. Yield 80%, colorless crystals, mp 139–142°С. 1Н NMR spectrum (СDCl3), δ, ppm (J, Hz): 2.07 quintet (2Н, СН2, J 6.5), 2.56 t (2Н, СН2, J 6.6), 2.75 t (2Н, СН2, J 6.4), 5.88 s (2Н, СН2), 7.31–7.36 m (1Н, НAr), 7.40–7.45 m (2Н, НAr), 7.80 s (1Н), 7.83–7.88 m (2Н, НAr), 16.42 br. s (1Н, ОН). 13С NMR spectrum (СDCl3), δC, ppm: 19.2, 31.9, 38.1, 58.0, 112.4, 121.8, 125.9, 128.3, 128.9, 130.7, 148.0, 195.8 (C1), 196.7 (C3), 197.0 (C1′). Found, %: C 64.72; H 5.13; N 14.18. C16H15N3O3. Calculated, %: C 64.64; H 5.09; N 14.13.

5,5-Dimethyl-2-[2-(4-phenyl-1Н-1,2,3-triazol-1-yl)acetyl]cyclohexane-1,3-dione (3b) was obtained from 5,5-dimethylcyclohexane-1,3-dione 1b and 2-(4-phenyl-1H-1,2,3-triazol-1-yl)acetic acid 2a. Yield 77%, colorless crystals, mp 136–138°С. 1Н NMR spectrum (СDCl3), δ, ppm: 1.13 s (6Н, 2СН3), 2.42 s (2Н, СН2), 2.61 s (2Н, СН2), 5.89 s (2Н, СН2), 7.31–7.36 m (1Н, НAr), 7.40– 7.45 m (2Н, НAr), 7.81 s (1Н), 7.83–7.88 m (2Н, НAr), 16.41 br. s (1Н, ОН). 13С NMR spectrum (СDCl3), δC, ppm: 28.3, 31.3, 45.4, 51.9, 57.9, 111.4, 121.8, 126.0, 128.3, 129.0, 130.7, 148.1, 195.6 (C1, C3), 196.6 (C1′). Found %: C 66.53; H 5.94; N 12.96. C18H19N3O3. Calculated, %: C 66.45; H 5.89; N 12.91.

2-[2-(4-Pentyl-1Н-1,2,3-triazol-1-yl]acetyl)cyclohexan-1,3-dione (3c) was obtained from cyclohexane-1,3-dione 1a and 2-(4-pentyl-1H-1,2,3-triazol-1-yl)acetic acid 2b. Yield 75%, colorless crystals, mp 68–71°С. 1Н NMR spectrum (СDCl3), δ, ppm (J, Hz): 0.85–0.91 m (3Н, СН3), 1.28–1.39 m (4Н, СН2), 1.63–1.74 m (2Н, СН2), 2.04 quintet (2Н, СН2, J 6.5), 2.53 t (2Н, СН2, J 6.6), 2.73 t (4Н, СН2, J 7.7), 5.78 s (2Н, СН2), 7.29 s (1Н), 16.45 br. s (1Н, ОН). 13С NMR spectrum (СDCl3), δC, ppm: 14.1, 19.2, 22.5, 25.8, 29.2, 31.6, 31.9, 38.1, 57.8, 112.4, 122.7, 148.7, 195.7 (C1), 196.6 (C3), 197.5 (C1′). Found, %: C 61.92; H 7.31; N 14.52. C15H21N3O3. Calculated, %: C 61.84; H 7.27; N 14.47.

5,5-Dimethyl-2-[2-(4-pentyl-1Н-1,2,3-triazol-1-yl)acetyl]cyclohexane-1,3-dione (3d) was obtained from 5,5-dimethylcyclohexane-1,3-dione 1b and 2-(4-pentyl-1H-1,2,3-triazol-1-yl)acetic acid 2b. Yield 75%, colorless crystals, mp 115–116°С. 1Н NMR spectrum (СDCl3), δ, ppm (J, Hz): 0.85–0.93 m (3Н, СН3), 1.11 s (6Н, СН3), 1.28–1.40 m (4Н, СН2), 1.68 quintet (2Н, СН2, J 7.5), 2.40 s (2Н, СН2), 2.58 s (2Н, СН2), 2.74 t (2Н, СН2, J 7.7), 5.79 s (2Н, СН2), 7.30 s (1Н), 16.43 br. s (1Н, ОН). 13С NMR spectrum (СDCl3), δC, ppm: 14.1, 22.5, 25.8, 28.3, 29.2, 31.3, 31.6, 45.4, 51.9, 57.7, 111.3, 122.7, 148.7, 195.6 (C1, C3), 197.0 (C1′). Found, %: C 63.85; H 7.86; N 13.10. C17H25N3O3. Calculated, %: C 63.93; H 7.89; N 13.16.

Triazole-containing 1,5,6,7-tetrahydro-4Н-indazol-4-ones 4a–4h. To solution of 37 mmol of 2-(triazolylacetyl)cyclohexane-1,3-dione 3a–3d in 15 mL of ethanol, 37 mmol (0.05 g) of phenylhydrazine hydrochloride [or 37 mmol of (0.06 g) of 4-fluorophenylhydrazine hydrochloride] and 37 mmol (0.02 g) of sodium hydroxide were added. The reaction mixture was stirred for 24 h at room temperature, and then 12.3 mmol (0.017 g) of phenylhydrazine hydrochloride and 12.3 mmol (0.01 g) of sodium hydrochloride [or 18.5 mmol (0.03 g) of 4-fluorophenylhydrazine hydrochloride and 18.5 mmol (0.01 g) of sodium hydroxide] were added and the reaction mixture was stirred for 24 h. Ethanol was removed, the residue was dissolved in 60 mL of chloroform, washed with diluted 1 : 10 hydrochloric acid (3×15 mL), water (2×15 mL), dried over anhydrous sodium sulfate. Chloroform was removed, and indazolones 4а–4h were isolated by column chromatography of the residue (71–87% yield).

1-Phenyl-3-[(4-phenyl-1Н-1,2,3-triazol-1-yl)methyl]-1,5,6,7-tetrahydro-4Н-indazol-4-one (4a). Yield 79%, colorless crystals, mp 146–147°С. 1Н NMR spectrum (СDCl3), δ, ppm (J, Hz): 2.13–2.21 m (2Н, СН2), 2.54–2.59 m (2Н, СН2), 2.96 t (2Н, СН2, J 6.1), 5.89 s (2Н, СН2), 7.27–7.32 m (1Н, НAr), 7.35–7.45 m (3Н, НAr), 7.46–7.52 m (4Н, НAr), 7.80–7.86 m (2Н, НAr), 8.18 s (1Н). 13С NMR spectrum (СDCl3), δC, ppm: 23.5, 23.7, 38.2, 46.5, 117.6, 121.0, 123.9, 125.9, 128.0, 128.7, 128.8, 129.6, 131.0, 138.3, 146.2, 147.8, 150.7, 194.0. Found, %: C 71.45; H 5.13; N 18.90. C22H19N5O. Calculated, %: C 71.53; H 5.18; N 18.96.

1-(4-Fluorophenyl)-3-[(4-phenyl-1Н-1,2,3-triazol-1-yl)methyl]-1,5,6,7-tetrahydro-4Н-indazol-4-one (4b). Yield 71%, colorless crystals, mp 161–162°С. 1Н NMR spectrum (СDCl3), δ, ppm (J, Hz): 2.13–2.23 m (2Н, СН2), 2.52–2.60 m (2Н, СН2), 2.92 t (2Н, СН2, J 6.2), 5.87 s (2Н, СН2), 7.15–7.22 m (2Н, НAr), 7.27–7.33 m (1Н, НAr), 7.35–7.42 m (2Н, НAr), 7.43–7.50 m (2Н, НAr), 7.80–7.85 m (2Н, НAr), 8.17 s (1Н). 13С NMR spectrum (СDCl3), δC, ppm (J, Hz): 23.4, 23.7, 38.2, 46.5, 116.6 d (2JCF 23.0), 117.6, 121.0, 125.8 d (3JCF 8.8), 125.9, 128.1, 128.9, 131.0, 134.5 d (4JCF 2.5), 146.3, 147.8, 150.7, 162.4 d (1JCF 249.4), 193.9. 19F NMR spectrum (СDCl3), δF, ppm: –111.87 to –111.96 m (1F). Found, %: C 68.30; H 4.72; N 18.14. C22H18FN5O. Calculated, %: C 68.21; H 4.68; N 18.08.

6,6-Dimethyl-1-phenyl-3-[(4-phenyl-1Н-1,2,3-triazol-1-yl)methyl]-1,5,6,7-tetrahydro-4Н-indazol-4-one (4c). Yield 82%, colorless crystals, mp 71–74°С. 1Н NMR spectrum (СDCl3), δ, ppm: 1.10 s (6Н, СН3), 2.44 s (2Н, СН2), 2.81 s (2Н, СН2), 5.89 s (2Н, СН2), 7.27– 7.31 m (1Н, НAr), 7.35–7.40 m (2Н, НAr), 7.40–7.45 m (1Н, НAr), 7.45–7.52 m (4Н, НAr), 7.80–7.85 m (2Н, НAr), 8.16 s (1Н). 13С NMR spectrum (СDCl3), δC, ppm: 28.5, 36.2, 37.2, 46.5, 52.3, 116.6, 120.9, 124.0, 125.9, 128.0, 128.7, 128.8, 129.6, 131.0, 138.3, 146.0, 147.8, 149.9, 193.4. Found, %: C 72.62; H 5.88; N 17.70. C24H23N5O. Calculated, %: C 72.52; H 5.83; N 17.62.

6,6-Dimethyl-1-(4-fluorophenyl)-3-[(4-phenyl-1Н-1,2,3-triazol-1-yl)methyl]-1,5,6,7-tetrahydro-4Н-indazol-4-one (4d). Yield 87%, colorless crystals, mp 84–87°С. 1Н NMR spectrum (СDCl3), δ, ppm: 1.10 s (6Н, СН3), 2.42 s (2Н, СН2), 2.76 s (2Н, СН2), 5.86 s (2Н, СН2), 7.14–7.21 m (2Н, НAr), 7.24–7.31 m (1Н, НAr), 7.34–7.41 m (2Н, НAr), 7.41–7.48 m (2Н, НAr), 7.78–7.84 m (2Н, НAr), 8.14 s (1Н). 13С NMR spectrum (СDCl3), δC, ppm (J, Hz): 28.5, 36.1, 37.0, 46.4, 52.2, 116.5, 116.5 d (2JCF 22.9), 120.9, 125.8 d (3JCF 8.8), 125.9, 128.1, 128.8, 130.9, 134.4 d (4JCF 2.5), 146.0, 147.8, 149.9, 162.3 d (1JCF 249.6), 193.3. 19F NMR spectrum (СDCl3), δF, ppm: –111.84÷–111.94 m (1F). Found, %: C 69.30; H 5.31; N 16.81. C24H22FN5O. Calculated, %: C 69.38; H 5.34; N 16.86.

3-[(4-Pentyl-1Н-1,2,3-triazol-1-yl)methyl]-1-phenyl-1,5,6,7-tetrahydro-4Н-indazol-4-one (4e). Yield 75%, colorless crystals, mp 44–46°С. 1Н NMR spectrum (СDCl3), δ, ppm (J, Hz): 0.82–0.89 m (3Н, СН3), 1.25–1.35 m (4Н, СН2), 1.63 quintet (2Н, СН2, J 7.6), 2.16 quintet (2Н, СН2, J 6.3), 2.50–2.57 m (2Н, СН2), 2.66 t (2Н, СН2, J 7.7), 2.95 t (2Н, СН2, J 6.1), 5.78 s (2Н, СН2), 7.37–7.43 m (1Н, НAr), 7.43–7.50 m (4Н, НAr), 7.64 s (1Н). 13С NMR spectrum (СDCl3), δC, ppm: 14.1, 22.5, 23.5, 23.7, 25.7, 29.2, 31.5, 38.2, 46.3, 117.5, 121.9, 123.8, 128.6, 129.5, 138.3, 146.4, 148.3, 150.6, 193.9. Found, %: C 69.49; H 6.97; N 19.35. C21H25N5O. Calculated, %: C 69.40; H 6.93; N 19.27.

3-[(4-Pentyl-1Н-1,2,3-triazol-1-yl)methyl]1-(4-fluorophenyl)-1,5,6,7-tetrahydro-4Н-indazol-4-one (4f). Yield 68%, colorless crystals, mp 42–45°С. 1Н NMR spectrum (СDCl3), δ, ppm (J, Hz): 0.82–0.90 m (3Н, СН3), 1.25–1.35 m (4Н, СН2), 1.63 quintet (2Н, СН2, J 7.3), 2.16 quintet (2Н, СН2, J 6.2), 2.53 t (2Н, СН2, J 6.4), 2.66 t (2Н, СН2, J 7.8), 2.91 t (2Н, СН2, J 6.2), 5.77 s (2Н, СН2), 7.11–7.20 m (2Н, НAr), 7.40–7.48 m (2Н, НAr), 7.64 s (1Н). 13С NMR spectrum (СDCl3), δC, ppm (J, Hz): 14.1, 22.5, 23.3, 23.6. 25.8, 29.2, 31.5, 38.1, 46.2, 116.5 d (2JCF 23.2), 117.5, 121.9, 125.8 d (3JCF 8.8), 134.5 d (4JCF 2.5), 146.5, 148.4, 150.6, 162.3 d (1JCF 249.4), 193.8. 19F NMR spectrum (СDCl3), δF, ppm: –112.00÷–112.10 m (1F). Found, %: C 66.21; H 6.39; N 18.44. C21H24FN5O. Calculated, %: C 66.12; H 6.34; N 18.36.

6,6-Dimethyl-3-[(4-pentyl-1Н-1,2,3-triazol-1-yl)methyl]-1-phenyl-1,5,6,7-tetrahydro-4Н-indazol-4-one (4g). Yield 72%, colorless oil. 1Н NMR spectrum (СDCl3), δ, ppm (J, Hz): 0.82–0.90 m (3Н, СН3), 1.09 s (6Н, СН3), 1.25–1.35 m (4Н, СН2), 1.63 quintet (2Н, СН2, J 7.3), 2.42 s (2Н, СН2), 2.67 t (2Н, СН2, J 7.7), 2.80 s (2Н, СН2), 5.79 s (2Н, СН2), 7.38–7.44 m (1Н, НAr), 7.44–7.52 m (4Н, НAr), 7.63 s (1Н). 13С NMR spectrum (СDCl3), δC, ppm: 14.1, 22.5, 25.8, 28.5, 29.2, 31.5, 36.1, 37.2, 46.3, 52.3, 116.5, 121.8, 123.9, 128.6, 129.5, 138.3, 146.2, 148.4, 149.7, 193.3. Found, %: C 70.47; H 7.42; N 17.80. C23H29N5O. Calculated, %: C 70.56; H 7.47; N 17.89.

6,6-Dimethyl-3-[(4-pentyl-1Н-1,2,3-triazol-1-yl)methyl]-1-(4-fluorophenyl)-1,5,6,7-tetrahydro-4Н-indazol-4-one (4h). Yield 84%, colorless crystals, mp 87–88°С. 1Н NMR spectrum (СDCl3), δ, ppm (J, Hz): 0.80–0.90 m (3Н, СН3), 1.09 s (6Н, СН3), 1.24–1.35 m (4Н, СН2), 1.62 quintet (2Н, СН2, J 7.3), 2.41 s (2Н, СН2), 2.66 t (2Н, СН2, J 7.7), 2.75 s (2Н, СН2), 5.77 s (2Н, СН2), 7.12–7.20 m (2Н, НAr), 7.39–7.47 m (2Н, НAr), 7.62 s (1Н). 13С NMR spectrum (СDCl3), δC, ppm (J, Hz): 14.1, 22.5, 25.7, 28.4, 29.2, 31.5, 36.1, 37.1, 46.2, 52.2, 116.5, 116.5 d (2JCF 23.2), 121.8, 125.8 d (3JCF 8.8), 134.4 d (4JCF 2.5), 146.3, 148.4, 149.8, 162.3 d (1JCF 249.4), 193.2. 19F NMR spectrum: from –111.91 to –112.10 m (1F). Found, %: C 67.38; H 6.82; N 17.03. C23H28FN5O. Calculated, %: C 67.46; H 6.89; N 17.10.

Triazole-containing 6,7-dihydrobenzo[d]isoxazol-4(5H)-ones 5a, 5c. To a solution of 54 mmol (0.16 g) of 2-(triazolylacetyl)cyclohexane-1,3-dione 3а, 3c in 15 mL of ethanol was added 54 mmol (0.04 g) of hydroxylamine hydrochloride and 54 mmol (0.02 g) of sodium hydroxide. The reaction mixture was refluxed for 8 h, ethanol was removed. Column chromatography of the residue gave 6,7-dihydrobenzo[d]isoxazol-4(5Н)-ones 5a, 5c in 81 and 61% yields, respectively.

3-[(4-Phenyl-1Н-1,2,3-triazol-1-yl)methyl]-6,7-dihydrobenzo[d]isoxazol-4(5Н)-one (5a). Yield 81%, colorless crystals, mp 107–109°С. 1Н NMR spectrum (СDCl3), δ, ppm (J, Hz): 2.24 quintet (2H, СН2, J 6.3), 2.49–2.57 m (2H, CH2), 3.02 t (2H, CH2, J 6.3), 5.84 s (2H, CH2), 7.29–7.34 m (1Н, НAr), 7.37–7.43 m (2Н, НAr), 7.79–7.85 m (2Н, НAr), 8.11 s (1Н). 13С NMR spectrum (СDCl3), δC, ppm: 22.3, 23.1. 37.8, 44.3, 114.4, 121.1, 125.9, 128.3, 128.9, 130.6, 148.1, 155.1, 182.4, 193.0. Found, %: C 65.21; H 4.73; N 18.97. C16H14N4O2. Calculated, %: C 65.30; H 4.79; N 19.04.

3-[(4-Pentyl-1Н-1,2,3-triazol-1-yl)methyl]-6,7-dihydrobenzo[d]isoxazol-4(5Н)-one (5c). Yield 61%, colorless crystals, mp 69–70°С. 1Н NMR spectrum (СDCl3), δ, ppm (J, Hz): 0.80–0.92 m (3Н, СН3), 1.25–1.37 m (4Н, СН2), 1.59–1.69 m (2H, CH2), 2.24 quintet (2H, СН2, J 6.4), 2.50–2.55 m (2H, CH2), 2.64–2.71 m (2H, CH2), 3.01 t (2H, CH2, J 6.3), 5.75 s (2H, CH2), 7.58 s (1Н). 13С NMR spectrum (СDCl3), δC, ppm: 22.4, 22.5, 23.1, 25.7, 29.1, 31.5, 37.8, 44.1, 114.4, 122.0, 148.8, 155.3, 182.3, 192.8. Found, %: C 62.40; H 6.93; N 19.38. C15H20N4O2. Calculated, %: C 62.48; H 6.99; N 19.43.

Triazole-containing 6,7-dihydrobenzo[d]isoxazol-4(5H)-ones 5b, 5d. To a solution of 37 mmol (0.12 g) of 5,5-dimethyl-2-(triazolylacetyl)cyclohexane-1,3-dione 3b, 3d in 15 mL of ethanol was added 37 mmol (0.03 g) of hydroxylamine hydrochloride and 37 mmol (0.02 g) of hydroxide sodium. The reaction mixture was refluxed for 8 h, kept at room temperature for 16 h, an additional 37 mmol (0.03 g) of hydroxylamine hydrochloride and 37 mmol (0.02 g) of sodium hydroxide were added, and the resulting reaction mixture was refluxed for 8 h. After removing the solvent, the target 6,7-dihydrobenzo[d]isoxazol-4(5H)-ones 5b, 5d were isolated by column chromatography in 71 and 67% yields, respectively.

6,6-Dimethyl-3-[(4-phenyl-1Н-1,2,3-triazol-1-yl)methyl]-6,7-dihydrobenzo[d]isoxazol-4(5Н)-one (5b). Yield 71%, colorless crystals, mp 156–157°С. 1Н NMR spectrum (СDCl3), δ, ppm: 1.15 s (6H, CH3), 2.42 s (2H, CH2), 2.87 s (2H, CH2), 5.85 s (2H, CH2), 7.28–7.34 m (1Н, НAr), 7.36–7.43 m (2Н, НAr), 7.78–7.84 m (2Н, НAr), 8.10 s (1Н). 13С NMR spectrum (СDCl3), δC, ppm: 28.5, 36.0. 36.8, 44.4, 52.2, 113.4, 121.0, 126.0, 128.3, 128.9, 130.6, 148.1, 155.0, 181.9, 192.3. Found, %: C 67.15; H 5.68; N 17.44. C18H18N4O2. Calculated, %: C 67.07; H 5.63; N 17.38.

5,5-Dimethyl-3-[(4-pentyl-1Н-1,2,3-triazol-1-yl)methyl]-6,7-dihydrobenzo[d]isoxazol-4(5Н)-one (5d). Yield 67%, colorless crystals, mp 37–40°С. 1Н NMR spectrum (СDCl3), δ, ppm: 0.84–0.90 m (3Н, СН3), 1.15 s (6H, CH3), 1.26–1.36 m (4Н, СН2), 1.58–1.69 m (2H, CH2), 2.41 s (2H, CH2), 2.65–2.71 m (2H, CH2), 2.86 s (2H, CH2), 5.76 s (2H, CH2), 7.57 s (1Н). 13С NMR spectrum (СDCl3), δC, ppm: 14.1, 22.5, 25.7, 28.5, 29.2, 31.5, 36.0, 36.8, 44.2, 52.3, 113.3, 121.9, 148.8, 155.2, 181.8, 192.2. Found, %: C 64.42; H 7.60; N 17.64. C17H24N4O2. Calculated, %: C 64.53; H 7.65; N 17.71.

Studies of cytotoxic activity were carried out on three cell lines: HepG2 (human hepatocellular carcinoma), MCF-7 (human mammary adenocarcinoma), and Hep2 (human laryngeal carcinoma), which were purchased from the State Research Center of Virology and Biotechnology “VECTOR.” Cell viability was assessed by double staining with Hoechst 33342 fluorescent dyes and propidium iodide (PI) according to the standard method. Cells were seeded on 96 well plates and cultured in IMDM medium in a CO2 incubator at 37°C. After 24 h, the compounds dissolved in DMSO were added in the concentration range of 1–100 μM and incubated for 48 h. Cells were stained with fluorescent dyes—Hoechst 33342 (Sigma-Aldrich) and propidium iodide (Invitrogen)—for 30 min at 37°C. Recording was performed on an IN Cell Analyzer 2200 (GE Healthcare, UK) in automatic mode, at least 4 fields per well. The obtained images were analyzed using the In Cell Investigator program to determine live, dead and apoptotic cells in the entire population. The result is presented as the percentage of cells from three independent experiments ± standard deviation.