Introduction

Quinolines and their derivatives with specific substituents at appropriate positions have attracted much interest in synthetic and medicinal chemistry. They have a wide range of chemotherapeutic activity including antimicrobial [1, 2], antimalarial [3, 4], antitumor [5], anti-inflammatory [6, 7], and antiparasitic [8] activity. The 3-substituted quinolines are small molecules reported to be potent and selective inhibitors of platelet-derived growth factor receptor (PDGFr) tyrosine kinase and non-TZD selective peroxisome proliferator-activated receptor gamma (PPARγ) agonists for type 2 diabetes [9, 10]. Among quinolines, 2-chloro-3-formylquinolines are versatile precursors and have been used as building blocks for synthesis of annulated quinolines with potential biological activity [11–13]. Our recent work has involved synthesis of multifunctionalized heterocyclic compounds for evaluation as antimicrobial [14–21] and anticancer agents [22, 23]. As a part of this work, new 3-hetarylquinolines were required for antibacterial and anticancer evaluation. N′-((2-Chloroquinolin-3-yl)methylene)-2-cyanoacetohydrazide (3) seemed a good starting material to fulfill this objective.

Results and discussion

Chemistry

The synthetic strategy adopted to obtain the target compounds is depicted in Schemes 1, 2, 3, 4, and 5. The starting material N′-((2-chloroquinolin-3-yl)methylene)-2-cyanoacetohydrazide (3) was obtained in two steps by gentle heating of acetanilide (1) with POCl3/DMF at 80 °C in the Vilsmeier–Haack reaction to afford 2-chloro-3-formylquinoline (2) [24]; this underwent condensation with 2-cyanoacetohydrazide in boiling ethanol to afford 3 as depicted in Scheme 1.

Scheme 1
scheme 1

Synthesis of N′-((2-chloroquinolin-3-yl)methylene)-2-cyanoacetohydrazide (3)

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Scheme 2
scheme 2

Synthetic route to pyrazole derivatives 5a–c

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Scheme 3
scheme 3

Synthetic route to pyridone derivatives 9a–d

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Scheme 4
scheme 4

Synthetic route to coumarin derivatives 10a–c and 11a–c

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Scheme 5
scheme 5

Synthetic route to 1,2,4-triazine derivative 13

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To show the synthetic potential of compound 3, its reactivity with aromatic aldehydes was examined. Thus, Knoevenagel condensation of 3 with aromatic aldehydes (benzaldehyde, p-tolualdehyde and p-anisaldehyde) and heterocyclic aldehydes (furfural and 2-formylthiophene) in ethanol under reflux containing a catalytic amount of piperidine furnished the corresponding arylidene derivatives 4a–e. The structure of compounds 4a–e was confirmed on the basis of elemental analysis and spectral data. For example, the IR spectrum of 4c contained absorption bands at 3,250, 2,208, 1,685, and 1,617 cm−1 ascribed to NH, nitrile, amidic C=O, and C=N functionaility, respectively. Its 1H NMR spectrum contained five singlet signals at δ 3.89, 8.25, 8.61, 8.98, and 12.27 ppm, assignable to methoxy protons, olefinic CH=, quinoline-H4, CH=N, and NH protons, respectively, and a multiplet in the region δ 7.18–8.08 ppm ascribed to eight aromatic protons. The 13C NMR spectrum contained 21 signals; the most important, at δ 55.7, 115.2, and 162.9 ppm, were ascribed to OCH3, CN, and C=O carbon, respectively. The mass spectrum contained the molecular ion peak at m/z = 390 (M+) corresponding to the molecular formula C21H15ClN4O2.

Treatment of 4a–c with hydrazine hydrate in ethanol, under reflux, furnished the pyrazolylquinoline derivatives 5a–c. The IR spectrum of compound 5b, as representative example, contained absorption bands at 3,421, 3,329, 3,193, 3,141, and 1,636 cm−1 ascribed to NH2, NH, amide-NH, and carbonyl functionality, respectively. The 1H NMR spectrum of 5b contained six singlet signals at δ 2.30, 6.50, 8.66, 9.10, 10.93, and 13.24 ppm assignable to CH3, NH2, quinoline-H4, CH=N, and amide-NH, and pyrazole NH protons, respectively. Its mass spectrum contained a molecular ion peak at m/z = 404 (M+) which corresponded to its molecular formula (C21H17ClN6O). Formation of compounds 5a–c is assumed to proceed via Michael addition of hydrazine hydrate to α,β-unsaturated nitrile 4a–c and in-situ intramolecular 1,5-dipolar cyclization via addition of an amino group to a nitrile function to give dihydropyrazole, which underwent autooxidation to give the target pyrazoles.

2-Pyridones are important heterocycles with great applicability in medicinal chemistry; this core structure can be found in compounds with diverse biological and medicinal applications [25]. Literature survey revealed that reaction of N-hetaryl-2-cyanoacetamides with either β-diketones or arylidene malononitriles is an efficient method for synthesis of 2-pyridones [26]. In this context, we investigated reaction of the active methylene group of compound 3 with a variety of arylidene malononitriles. Thus, treatment of 3 with a series of arylidene malononitriles 6 in boiling ethanol containing a catalytic amount of piperidine afforded the 2-pyridone derivatives 9a–d (Scheme 3).

Elemental analysis and spectroscopic data confirmed the proposed structures of products 9a–d. The IR spectrum of compound 9a, as example, contained absorption bands at 3,350, 3,243, 2,212, 1,647, and 1,608 cm−1, ascribed to NH2, CN, C=O, and C=N functionality, respectively. Its 1H NMR spectrum contained four singlet signals at δ 3.84, 6.87, 8.76, and 9.00 ppm assignable to methoxy, NH2 proton, quinoline-H4, and CH=N protons, respectively, and a multiplet in the region δ 7.08–8.12 ppm ascribed to eight aromatic protons. The 13C NMR spectrum contained 24 signals, the most important of which at δ 117.3, 117.5, and 161.9 ppm were ascribed to two unsymmetrical CN and C=O carbon atoms, respectively. The mass spectrum of 9a contained the molecular ion peak at m/z = 454 (M+), corresponding to the molecular formula C24H15ClN6O2. The mass fragmentation pattern of pyridone 9a, shown in Fig. 1, confirmed its chemical structure.

Fig. 1
figure 1

Mass fragmentation pattern of compound 9a

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The mechanism of formation of pyridones 9a–d is depicted in Scheme 3. Presumably, the reaction path includes the Michael addition of CH acid 3 to the β-carbon of the arylidene malononitriles 6 with formation of intermediate 7 which undergoes chemoselective heterocyclization via nucleophilic addition of the amidic NH to a nitrile function affording intermediate 8 which subsequently undergoes tautomerism with elimination of a hydrogen molecule to give the substituted 2-pyridones 9a–d.

As an extension of this study, the behavior of 3 toward 2-hydroxybenzaldehydes as a convenient synthetic route to some new coumarins incorporating the quinoline structure was also investigated. Thus, condensation of 3 with salicylaldehyde, 5-bromosalicylaldehyde, and 5-nitrosalicylaldehyde in boiling ethanolic piperidine solution furnished the 2-iminocoumarin derivatives 10a–c. The structures of these products were confirmed by IR spectroscopy which revealed the absence of a nitrile function and the appearance of absorption bands in the regions 3,354–3,284, 1,662–1,654, and 1,615–1,610 cm−1 characteristic of NH, C=O, and C=N functionality, respectively. Their 1H NMR spectra revealed a coumarin-H4 proton as a singlet signal resonating at approximately δ 7.96 ppm, and the other signals expected (Scheme 4). The iminocoumarins 10a–c were converted to coumarins 11a–c upon warming in ethanol containing a catalytic amount of conc. HCl. Surprisingly, chemical testing of the isolated products revealed the absence of chlorine atoms, and the IR spectrum of 11b contained five strong absorption bands at 3,448, 3,258, 1,717, 1,670, and 1,655 cm−1 assignable to two amidic NH, C=O, and amidic carbonyl functionality, respectively. Its 1H NMR spectrum contained four singlets at δ 8.26, 8.34, 8.85, and 9.07 ppm assignable to coumarin-H5, coumarin-H4, quinoline-H4, and CH=N protons, respectively, and two singlets, exchangeable with D2O, at δ 10.18 and 12.10 ppm, assigned to two amidic NH protons, and the multiplet signal centered around δ 7.35–8.09 ppm which integrated to six aromatic protons. The 13C NMR spectrum of compound 11b contained 20 signals, the most important of which at δ 157.9, 165.4, and 177.2 ppm were characteristic of three carbonyl carbons. The mass spectra of coumarins 11a–c contained molecular ion peaks (M+) in agreement with their molecular formulas. This analysis proved the structures of 11a–c as the reaction products.

A plausible mechanism for formation of coumarins 10a–c and 11a–c may be initial Knoevenagel condensation of the active methylene nitrile of 3 with carbonyl groups of the salicylaldehyde derivatives followed by intramolecular 1,6-dipolar cyclization via addition of a phenolic OH group to the nitrile function to give the isolated iminocoumarins 10a–c; these underwent acid-catalyzed hydrolysis to afford the target coumarins 11a–c.

The behavior of compound 3 toward diazotized aromatic amines as potential precursors for hydrazonyl nitriles was also investigated. Thus, coupling of compound 3 with a series of diazotized aromatic amines in pyridine at 0–5 °C furnished the arylhydrazones 12a–c in excellent yields (Scheme 5). Formation of arylhydrazones, rather than arylazo derivatives (CH–azo), was established from their IR spectra, which contained absorption bands in the regions 2,215–2,209 and 1,700–1,696 cm−1, ascribed to conjugated CN and C=O functionality, respectively. In addition, their 1H NMR spectra contained no singlet peak at δ 5.72 ppm, characteristic of the CH proton of the CH–azo compounds [27]. It is important to mention that arylhydrazones 12a–c can occur as two geometric structures, the E and Z configurations. Predominant formation of the Z configuration was apparent from their 1H NMR spectra which contained the hydrazone proton (C=N–NH) signal at δ = 11.90–11.94 ppm, which agrees with previous reports for similar hydrazones [28].

We next investigated the heterocyclization of hydrazonyl nitrile 12a with formalin. Thus, treatment of 12a with formalin in ethanol under reflux containing a catalytic amount of piperidine afforded, as sole product, in moderate yield, the 1,2,4-triazin-5-one derivative 13. The IR spectrum of 13 contained absorption bands at 2,212, 1,701, and 1,617 cm−1 ascribed to CN, C=O, and C=N functionality, respectively. The 1H NMR spectrum contained three sharp singlets at δ 4.50, 8.65, and 9.70 ppm, ascribed to CH2, quinoline-H4, and CH=N protons, and multiplet at δ 7.26–7.86 ppm region ascribed to nine aromatic protons. The 13C NMR spectrum contained signals from 18 types of carbon atom; the most important signals at δ 76.6 and 163.9 ppm were characteristic of methylene and cyclic amidic carbonyl carbon atoms, respectively. Moreover, the mass spectrum of 13 contained a molecular ion peak at m/z = 388 (M+) corresponding to the molecular formula C20H13ClN6O. The mass fragmentation pattern depicted in Fig. 2 confirms its chemical structure.

Fig. 2
figure 2

Mass fragmentation pattern of compound 13

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Pharmacology

Antibacterial evaluation

Antibacterial screening of the compounds studied, to determine minimum inhibitory concentrations, was performed at the Microanalytical Center, Faculty of Science, Cairo University, Egypt. The compounds were tested to determine their in-vitro antibacterial activity against the human pathogens Bacillus subtilis, Streptococcus faecalis, and Pseudomonas aeruginosa, as examples of Gram-positive bacteria, and Staphylococcus aureus, Escherichia coli, and Neisseria gonorrhoeae, as examples of Gram-negative bacteria. Preliminary screening for antibacterial activity was performed by the disk-diffusion method [29]. The results are recorded in Table 1 as the average diameter of zones of inhibition (IZ) of microbial growth around the disks (mm). The concentration tested was 5 mg/mL and ampicillin was used as reference drug.

Table 1 Mean diameter of inhibition zone (mm) as indicator of the antibacterial activity of the newly synthesized compounds
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The results listed in Table 1 reveal that nine of the 22 compounds tested had obvious inhibitory effect against the growth of Gram-positive and Gram-negative bacteria. All the compounds tested had moderate to high activity against the Gram-positive microorganisms (B. subtilis, S. faecalis, S. aureus; inhibition zones varied from 9 to 16 mm compared with 18–20 for ampicillin) and against the Gram-negative bacteria (P. aeruginosa, E. coli, N. gonorrhoeae; inhibition zones varied from 9 to 16 mm).

Compounds 9a–c had the most potent effects against the Gram-positive bacteria (B. subtilis, S. faecalis, S. aureus) and compounds 9b and c were very potent against the Gram-positive bacteria B. subtilis and S. faecalis with inhibition zones of 15 mm, compared with 20 mm for ampicillin. Compound 9b had an effect against S. aureus close to that of ampicillin. The other compounds had a wide range of activity against all the Gram-positive bacteria tested, with weak to moderate potency.

The antibacterial activity of the compounds against Gram-negative bacteria are also listed in Table 1. Compounds 9a–c resulted in the largest inhibition zones, 15, 16, and 15 mm, respectively, against P. aeruginosa, compared with 17 mm for ampicillin. Compounds 9b and c were, moreover, very potent against E. coli with inhibition zones of 16 and 14 mm, respectively, compared with 22 mm for ampicillin. Compounds 9b and c had relatively high growth inhibitory activity against N. gonorrhoeae (IZ 14 mm). The other compounds had moderate to weak activity against growth of the different Gram-negative bacteria, with inhibition zones varying from 9 to 12 mm.

Study of the structures of the active compounds revealed they were mainly pyridones (9a–d) or coumarins (11a and c). Among the pyridones (9a–d), the nature of the substituent at position 4 on the phenyl ring seems to affect antibacterial activity. In this regard, the presence of such electron-withdrawing groups as Cl or F in pyridones 9b or 9c enhanced their antibacterial activity whereas the presence of the electron-donating group OCH3 in pyridone 9a reduced its antimicrobial activity. With regard to the second series, coumarins 11a and c had moderate antibacterial activity against S. aureus. Substituting the hydrogen atom at position 6 of the coumarin ring with an electron-withdrawing NO2 group (11c), resulted in dramatic enhancement of activity against all the organisms tested.

Anticancer evaluation

The cytotoxic effects of the newly synthesized compounds against four human tumor cell lines, breast cancer (MCF-7), non-small cell lung (NCI-H460), central nervous system (SF-268), and lung fibroblasts WI-38, were evaluated at the National Institute of Cancer, Cairo, Egypt. Doxorubicin was used as reference drug.

The results revealed that the compounds in Table 2 had variable inhibitory activity against the cell lines. With regard to activity against MCF-7, NCI-H460, and SF-268, the highest cytotoxic activity was observed for compounds 4a, d, 9a, c, 10c, 11c, 12c, and 13. The other compounds had weak to moderate inhibitory activity. Interestingly, compound 4d was more active than doxorubicin against MCF-7 and NCI-H460, with IC50 of 0.01 and 0.02 μg/mL, respectively.

Table 2 Cytotoxicity (IC50) of the tested compounds against different cell lines
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Compounds 9a, c, and 13 had the highest IC50 of 0.04, 0.07, and 0.02 μg/mL, respectively, against NCI-H460 compared with 0.09 μg/mL for doxorubicin. Similarly, compounds 9a, 12c, and 13 had higher activity (0.021, 0.02, and 0.01 μg/mL) than doxorubicin (IC50 0.09 μg/mL) against SF-268. The other compounds had a wide range of activity against the three cell lines MCF-7, NCI-H460, and SF-268. Some of the compounds tested had high growth-inhibitory activity against WI-38. The best activity was that of 10b and 12c.

With regard to structure–activity relationships (SAR) for the compounds, the acrylamide 4d and the pyridones 9a and c were the most active against cell lines MCF-7 and NCI-H460. The 1,2,4-triazine 13 was most active against NCI-H460 and SF-268. Cyclization of arylhydrazononitrile 12 to the 1,2,4-triazine resulted in enhanced anticancer activity. Conversion of acrylamides 4 to aminopyrazoles 5 resulted in reduced anticancer activity. Among the coumarin series, coumarin 11c, with the powerful electron-withdrawing NO2 group, was most active against MCF-7. The sensitivity of the cell lines to 3-hetarylquinolines was in the descending order NCI-H460 > SF-268 > MCF-7 > WI-38.

Conclusion

The purpose of this study was to synthesize new 3-hetarylquinolines and to investigate their antibacterial and anticancer activity, in the hope of discovering new structures which might lead to the development of potent antibacterial and anticancer agents. We synthesized four different groups of compounds with hybrid structures containing, basically, the quinoline group linked to pyrazole, pyridone, coumarin, or 1,2,4-triazine groups. The results obtained clearly showed that compounds derived from coumarins and pyridones had better antibacterial activity and that compounds derived from pyridones and 1,2,4-triazine had excellent anticancer activity.

Experimental

The chemicals used for synthesis were obtained from Aldrich and Sigma, and were used without further purification. The solvents used were of analytical-grade. Melting points were determined by use of a Stuart SMP11 apparatus and are uncorrected. Elemental analysis was performed at the Central Laboratories, Faculty of Science, King Saud University; the results were in satisfactory agreement with calculated values. IR spectra were acquired (KBr) by use of a Thermo Scientific Smart Omni-Transmission spectrophotometer at the Faculty of Science, King Khalid University. 1H NMR and 13C NMR spectra were acquired by use of Bruker NMR 500 MHz Ultra Shield, in DMSO-d 6 and CF3COOD as solvents, at the Faculty of Science, King Khalid University, Saudi Arabia. Mass spectra were acquired with a Finnegan MAT 212 instrument, at the Microanalytical Unit, Faculty of Science, Cairo University. 2-Chloro-3-formylquinoline (2) and N′-((2-chloroquinolin-3-yl)methylene)-2-cyanoacetohydrazide (3) were prepared as reported elsewhere [7, 24].

General procedure for synthesis of acrylohydrazide derivatives 4a–e

A mixture of compound 3 (0.79 g, 0.002 mol) and an aromatic aldehyde (0.002 mol) in absolute ethanol (30 mL) containing piperidine (three drops) was heated under reflux for 4 h. The precipitate obtained was isolated by filtration, dried well, and recrystallized from 1:2 EtOH–DMF to give compounds 4a–e.

N′-((2-Chloroquinolin-3-yl)methylene)-2-cyano-3-phenylacrylohydrazide (4a)

Yellow powder; yield 63 %; mp = 229–230 °C; IR (KBr) υmax/cm−1 = 3,175 (NH), 2,220 (CN), 1,673 (C=O, amidic), 1,617 (C=N), 1,595 (C=C, conjugated), 750 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 7.62 (t, J = 7.5 Hz, 1H, Ar–H4), 7.63 (t, J = 7.5 Hz, 2H, Ar3,5), 7.71 (t, J = 7.5 Hz, 1H, quinoline-H6), 7.89 (t, J = 7.5 Hz, 1H, quinoline-H6), 8.00 (d, J = 7.5 Hz, 2H, Ar–H2,6), 8.03 (d, J = 6 Hz, 1H, quinoline-H8), 8.25 (d, J = 6 Hz, 1H, quinoline-H5), 8.36 (s, 1H, quinoline-H4), 8.95 (s, 1H, CH=, olefinic), 8.98 (s, 1H, CH=N), 12.37 (s, 1H, NH); 13C NMR (DMSO-d 6 ): δppm = 105.2 (C= CN), 115.9 (CN), 125.8 (quinoline-C3), 126.8 (quinoline-C4a), 127.6 (quinoline-C6), 127.9 (Ar–C4), 129.1 (quinoline-C8), 130.2 (Ar–C3,5), 131.8 (quinoline-C7), 131.9 (Ar–C2,6), 132.8 (Ar-C1), 136.0 (quinoline-C7), 144.6 (C=N), 147.3 (quinoline-C8a), 148.5 (C–Ar), 151.9 (quinoline-C2), 158.5 (C=O); MS m/z (%) = 360 (M+, 1.7), 283 (1.2), 232 (4.2), 204 (1.8), 205 (0.5),190 (3.0), 189(11.1), 172 (26.6), 171 (100), 162 (0.5), 156 (38.55),122 (0.1),120 (0.2); Anal. Calcd. for C20H13ClN4O (360.79): C, 66.58; H, 3.63; N, 15.53 %, Found: C, 66.55; H, 3.60; N, 15.50 %.

N′-((2-Chloroquinolin-3-yl)methylene)-2-cyano-3-p-tolylacrylohydrazide (4b)

Yellow powder; yield 58 %; mp = 209–210 °C; IR (KBr) υmax/cm−1 = 3,284 (NH), 2,212 (CN), 1,692 (C=O, amidic), 1,617 (C=N), 1,589 (C=C, conjugated), 757 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 2.42 (s, 3H, CH3),7.43 (d, J = 8 Hz, 2H, Ar–H3,5), 7.72 (t, J = 7.5 Hz, 1H, quinoline-H6), 7.89 (t, J = 7.5 Hz, 1H, quinoline-H7), 7.95 (t, J = 7.5 Hz, 2H, Ar–H2,6), 7.98 (d, J = 8.5 Hz, 1H, quinoline-H5), 8.27 (d, J = 8.5 Hz, 1H, quinoline-H8), 8.31 (s, 1H, quinoline-H4), 8.95 (s, 1H, CH=, olefinic), 8.98 (s, 1H, CH=N), 12.32 (s, 1H, NH); 13C NMR (DMSO-d 6 ): δppm = 21.3 (CH3), 104.9(C–CN),116.7(CN), 125.8 (quinoline-C3), 126.8 (quinoline-C4a), 127.7 (quinoline-C6), 127.9 (quinoline-C8), 129.1 (quinoline-C5), 129.9 (Ar–C2,6), 130.4 (Ar–C3,5), 131.9 (Ar–C1), 132.7 (quinoline-C7), 136.0 (Ar–C4), 139.9 (quinoline-C4), 147.3 (quinoline-C8a), 148.8 (C–Ar),151.8 (quinoline-C2), 168.9 (C=O); MS m/z (%) = 374 (M+, 1.2), 359 (8.1), 283 (0.9), 232 (10.1), 204 (1.6), 205 (0.4),190 (11.1), 189 (2.7), 186 (25.9), 185 (100),162 (1.1), 142 (19.2); Anal. Calcd. for C21H15ClN4O (374.82): C, 67.29; H, 4.03; N, 14.95 %, Found: C, 67.25; H, 4.00; N, 14.91 %.

N′-((2-Chloroquinolin-3-yl)methylene)-2-cyano-3-(4-methoxyphenyl) acrylohydrazide (4c)

Yellow powder; yield 42 %; mp = 191–192 °C; IR (KBr) υmax/cm−1 = 3,250 (NH), 2,208 (CN), 1,685 (C=O, amidic), 1,617 (C=N), 1,585 (C=C, conjugated), 757 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 3.89 (s, 3H, OCH3), 7.18 (d, J = 8.5 Hz, 2H, Ar–H3,5), 7.71 (t, J = 7 Hz, 1H, quinoline-H6), 7.89 (t, J = 7 Hz, 1H, quinoline-H7), 7.96 (d, J = 9.5 Hz, 1H, quinoline-H8), 8.00 (d, J = 8.5 Hz, 2H, Ar–H2,6), 8.08 (d, J = 9.5 Hz, 1H, quinoline-H5), 8.25 (s, 1H, quinoline-H4), 8.61 (s, 1H, CH=, olefinic), 8.98 (s, 1H, CH=N), 12.27 (s, 1H, NH); 13C NMR (DMSO-d 6 ): δppm = 55.7 (OCH3), 104.5 (C–CN), 114.9 (Ar–C3,5), 115.2 (CN), 123.6 (quinoline-C3), 124.5 (Ar–C1), 126.8 (quinoline-C4a), 127.6 (quinoline-C6), 127.9 (quinoline-C8), 129.1 (quinoline-C5), 131.9 (Ar–C2,6), 132.9 (quinoline-C7), 135.9 (quinoline-C4), 143.7(CH=N), 147.2 (quinoline-C8a),149.5 (C–Ar), 152.7 (quinoline-C2), 161.7(Ar–C4), 162.9(C=O); MS m/z (%) = 390 (M+, 1.2), 283 (6.9), 257 (7.9), 204 (8.6), 205 (7.3), 201 (92.5), 189 (10.2), 186 (100), 177 (17.4), 158 (51.8), 107 (8.9), 77 (46.7); Anal. Calcd. for C21H15ClN4O2 (390.82): C, 64.54; H, 3.87; N, 14.34 %, Found: C, 64.51; H, 3.84; N, 14.30 %.

N′-((2-Chloroquinolin-3-yl)methylene)-2-cyano-3-(furan-2-yl)acrylohydrazide (4d)

Green crystals; yield 78 %; mp > 300 °C; IR (KBr) υmax/cm−1 = 3,251 (NH), 2,201 (CN), 1,654 (C=O, amidic), 1,617 (C=N), 1,577 (C=C, conjugated),777 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 6.95 (t, J = 4.5 Hz, 1H, furan-H4), 7.66 (t, J = 7.5 Hz, 1H, quinoline-H6), 7.68 (d, J = 6 Hz, 1H, furan-H3), 7.74 (t, J = 7.5 Hz, 1H, quinoline-H7), 7.90 (d, J = 8 Hz, 1H, quinoline-H5), 8.08 (d, J = 8 Hz, 1H, quinoline-H8), 8.22 (s, 1H, quinoline-H4), 8.26 (d, J = 6 Hz, 1H, furan-H5), 8.76 (s, 1H, CH=, olefinic), 9.02 (s, 1H, CH = N), 12.15 (s, 1H, NH); 13C NMR (DMSO-d 6 ): δppm=110.9 (furan-C3), 112.2 (furan-C4), 113.8 (C–CN), 115.1 (CN), 124.2 (quinoline-C3), 126.5 (quinoline-C4a), 127.0 (quinoline-C6), 127.9 (quinoline-C8), 128.4 (quinoline-C5), 131.8 (quinoline-C7), 136.3 (quinoline-C4), 144.2 (CH=N), 145.7 (furan-C4), 149.1 (quinoline-C8a), 150.0 (furan-C2), 152.7 (quinoline-C2), 154.7 (=C-Furan), 166.9 (C = O); MS m/z (%) = 350 (M+, 61.8), 283 (79.8), 204 (11.2), 175 (58.4), 171 (100), 147 (67.4), 118 (51.7), 67 (6.7); Anal. Calcd. for C18H11ClN4O2 (350.76): C, 61.64; H, 3.16; N, 15.97 %, Found: C, 61.60; H, 3.12; N, 15.94 %.

N′-((2-Chloroquinolin-3-yl)methylene)-2-cyano-3-(thiophen-2yl)acrylohydrazide (4e)

Yellow powder; yield 62 %; mp = 216–217 °C; IR (KBr) υmax/cm−1 = 3,190 (NH), 2,208 (CN), 1,661 (C=O, amidic), 1,618 (C=N), 1,577 (C=C, conjugated), 787 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 7.37 (t, J = 4.5 Hz, 1H, thiophene-H4), 7.71 (t, J = 7 Hz, 1H, quinoline-H6), 7.88 (t, J = 7.0 Hz, 1H, quinoline-H7), 8.00 (d, J = 8.5 Hz, 1H, quinoline-H5), 8.01(d, J = 5 Hz, 1H, thiophene-H3), 8.18 (d, J = 5 Hz, 1H, thiophene-H5), 8.25 (d, J = 8.5 Hz, 1H, quinoline-H8), 8.60 (s, 1H, quinoline-H4), 8.97 (s, 1H, CH=,olefinic), 8.98 (s, 1H, CH=N), 12.27 (s, 1H, NH); 13C NMR (DMSO-d 6 ): δppm = 98.8 (C–CN), 114.5 (CN), 126.8 (quinoline-C3), 127.7 (quinoline-C4a), 127.9 (quinoline-C6), 128.7 (quinoline-C8), 129.1 (quinoline-C5), 131.9 (thiophene-C4), 135.8 (thiophene-C3), 135.9 (thiophene-C5), 139.5 (quinoline-C7), 142.2 (quinoline-C4), 143.6 (thiophene-C2), 147.2 (CH=N), 148.4 (quinoline-C8a), 149.3 (quinoline-C2), 151.2 (=C-Thiophene), 168.1 (C=O); MS m/z (%) = 366 (M+, 0.8), 283 (0.2), 257 (10.02), 232 (0.2), 205 (0.5), 204 (2.3), 190 (1.0), 189 (2.1), 178 (30.6), 177 (100), 162 (79.2), 134 (61.3), 82 (2.4); Anal. Calcd. for C18H11ClN4OS (366.82): C, 58.94; H, 3.02; N, 15.27 %, Found: C, 58.90; H, 3.00; N, 15.23 %.

General procedure for the synthesis of pyrazolylquinoline derivatives 5a–c

A mixture of compound 4a, b, or c (0.001 mol) and hydrazine hydrate (1 mL, 0.002 mol) in ethanol (30 mL) was heated under reflux for 4 h. The reaction mixture was left to cool to room temperature then poured on to ice-cold water (25 mL). The solid product obtained was collected by filtration, washed with water, dried, and recrystallized from 1:4 DMF–EtOH to give compounds 5a–c.

3-Amino-N′-((2-chloroquinolin-3-yl)methylene)-5-phenyl-1H-pyrazole-4-carbohydrazide (5a)

Yellow crystals; yield 55 %; mp > 300 °C; IR(KBr) υmax/cm−1 = 3,421, 3,329 (NH2), 3,193 (NH), 3,141(NH, amidic), 1,636 (C=O, amidic), 1,616 (C=N), 1,596 (C=C, conjugated), 751 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 6.45 (s, 1H, NH2), 7.37 (t, J = 6 Hz, 1H, Ar–H4), 7.43 (t, J = 7.5 Hz, 2H, Ar–H3,5), 7.55 (t, J = 7 Hz, 1H, quinoline-H6), 7.62 (t, J = 7 Hz, 1H, quinoline-H7), 7.77 (d, J = 7.5 Hz, 2H, Ar–H2,6), 7.80 (d, J = 6.5 Hz, 1H, quinoline-H8), 7.98 (d, J = 6.5 Hz, 1H, quinoline-H5), 8.20 (s, 1H, quinoline-H4), 9.00 (s, 1H, CH=N), 10.90 (s, 1H, NH), 13.00 (s, 1H, NH); 13C NMR (DMSO-d 6 ): δppm = 93.4 (pyrazole-C4), 123.9 (quinoline-C3), 124.6 (pyrazole-C5), 126.0 (quinoline-C4a), 127.1 (quinoline-C6), 127.7 (Ar-C2,6), 127.9 (quinoline-C8), 128.0 (quinoline-C5), 128.6 (Ar–C4), 129.4 (Ar–C3,5), 131.5 (quinoline-C7), 132.8 (Ar–C1), 138.1 (quinoline-C4), 143.6 (CH=N), 149.0 (quinoline-C8a), 151.9 (quinoline-C2), 153.0 (pyrazole-C3), 162.7 (C=O); MS m/z (%) = 390 (M+, 61.7), 355 (65.9), 280 (30.9), 264 (89.4), 229 (2.1), 223 (55.3), 219 (100), 159 (3.2),158 (25.5),152 (20.2); Anal. Calcd. for C20H15ClN6O (390.83): C, 61.46; H, 3.87; N, 21.50 %, Found: C, 61.43; H, 3.83; N, 21.54 %.

3-Amino-N′-((2-chloroquinolin-3-yl)methylene)-5-p-tolyl-1H-pyrazole-4-carbohydrazide (5b)

Yellow powder; yield 70 %; mp = 126–127 °C; IR (KBr) υmax/cm−1: 3,421,3,329 (NH2), 3,193 (NH), 3,141(NH, amidic), 1,636 (C=O, amidic), 1,594 (C=C, conjugated), 751 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 2.30 (s, 3H, CH3), 6.50 (s, 1H, NH2), 7.23 (d, J = 6 Hz, 2H, Ar–H3,5), 7.62 (t, J = 7 Hz, 1H, quinoline-H6), 7.67 (d, J = 6 Hz, 2H, Ar–H2,6), 7.70 (t, J = 7 Hz, 1H, quinoline-H7), 7.88 (d, J = 6.5 Hz, 1H, quinoline-H8), 8.00 (d, J = 6.5 Hz, 1H, quinoline-H5), 8.66 (s, 1H, quinoline-H4), 9.10 (s, 1H, CH=N), 10.93 (s, 1H, NH), 13.24 (s, 1H, NH, Pyrazole); 13C NMR (DMSO-d 6 ): δppm = 22.1 (CH3), 90.9 (pyrazole-C4), 124.0 (quinoline-C3), 125.3 (pyrazole-C5), 126.5 (quinoline-C4a), 127.0 (quinoline-C6), 127.5 (quinoline-C8), 128.0 (quinoline-C5), 128.7 (Ar–C2,6), 129.1 (Ar–C3,5), 130.3 (Ar–C1), 131.2 (quinoline-C7), 132.0 (Ar–C4), 137.7 (quinoline-C4), 143.4 (CH=N), 148.9 (quinoline-C8a), 152.0 (quinoline-C2), 154.5 (pyrazole-C3), 163.3 (C=O); MS m/z (%) = 404 (M+, 10.2), 389 (0.2), 347 (0.9), 314 (4.9), 313 (0.7), 309 (4.7), 307 (100), 216 (5.6), 190 (1.9), 189 (3.6), 162 (7.4); Anal. Calcd. for C21H17ClN6O (404.85): C, 62.30; H, 4.23; N, 20.76 %, Found: C, 62.34; H, 4.20; N, 20.72 %.

3-Amino-N′-((2-chloroquinolin-3-yl)methylene)-5-(4-methoxyphenyl)-1H-pyrazole-4-carbohydrazide (5c)

Yellow powder; yield 55 %; mp = 151–152 °C; IR (KBr) υmax/cm−1 = 3,420, 3,329 (NH2), 3,193 (NH), 3,141(NH, amidic) 1,636 (C=O, amidic),1,604 (C=N), 1,583 (C=C, conjugated), 750 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 3.80 (s, 3H, CH3), 6.51 (s, 1H, NH2), 7.13 (d, J = 6 Hz, 2H, Ar–H3,5), 7.60 (t, J = 7.5 Hz, 1H, quinoline-H6), 7.64 (d, J = 6 Hz, 2H, Ar–H2,6), 7.71 (t, J = 7.5 Hz, 1H, quinoline-H7), 7.85 (d, J = 7 Hz, 1H, quinoline-H8), 8.06 (d, J = 7 Hz, 1H, quinoline-H5), 8.71 (s, 1H, quinoline-H4), 9.22 (s, 1H, CH=N), 10.88 (s, 1H, NH), 13.17 (s, 1H, NH, Pyrazole); 13C NMR (DMSO-d 6 ): δppm = 53.7 (OCH3), 91.0 (pyrazole-C4), 115.1 (Ar–C3,5), 124.2 (quinoline-C3), 125.6 (pyrazole-C5), 126.0 (Ar–C1), 126.4 (quinoline-C4a), 127.3 (quinoline-C7), 127.8 (quinoline-C8), 128.1 (quinoline-C5), 128.4 (Ar–C2,6), 131.0 (quinoline-C7), 137.5 (quinoline-C4), 143.4 (CH=N), 149.1 (quinoline-C8a), 152.0 (quinoline-C2), 154.5 (pyrazole-C3), 160.0 (Ar–C4), 163.1 (C=O); MS m/z (%) = 420 (M+, 39.5), 405 (33.7), 385 (33.1), 355 (42.4), 341 (41.3), 144 (33.1), 143 (33.7), 78 (10.5), 77 (100), 68 (36.6); Anal. Calcd. for C21H17ClN6O2 (420.85): C, 59.93; H, 4.07; N, 19.97 %, Found: C, 59.90; H, 4.03; N, 19.94 %.

General procedure for the synthesis of 2-pyridone derivatives 9a–d

Arylidene malononitriles 6 (0.004 mol) were added to a solution of compound 3 (1 g, 0.004 mol) in absolute ethanol (30 mL) containing three drops of piperidine. The reaction mixture was heated under reflux for 6 h, then left to cool to room temperature. The solid product formed upon pouring on to ice–water (20 mL) was collected by filtration, dried, and recrystallized from 4:1 EtOH–DMF to give compounds 9a–d.

6-Amino-1-((2-chloroquinolin-3-yl)methylene-amino)-4-(4-methoxyphenyl)-2-oxo-1,2-dihydropyridine-3,5-dicarbonitrile (9a)

Yellow powder; yield 78 %; mp = 246–247 °C; IR (KBr) υmax/cm−1 = 3,350, 3,243 (NH2), 2,212 (CN), 1,647 (C=O, amidic), 1,608 (C=N), 1,559 (C=C, conjugated), 1,387 (CH3), 757 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 3.84 (s, 3H, OCH3), 6.87 (s, 2H, NH2), 7.08 (d, J = 9 Hz, 2H, Ar–H3,5), 7.10 (d, J = 9 Hz, 2H, Ar–H2,6), 7.48 (t, J = 7.5 Hz, 1H, quinoline-H6), 7.51 (t, J = 7.5 Hz, 1H, quinoline-H7), 8.10 (d, J = 6.5 Hz, 1H, quinoline-H8), 8.12 (d, J = 6.5 Hz, 1H, quinoline-H5), 8.76 (s, 1H, quinoline-H4), 9.00 (s, 1H, CH=N); 13C NMR (DMSO-d 6 ): δppm = 55.2 (CH3), 78.1 (pyridine-C5), 114.2 (Ar–C3,5), 116.9 (pyridine-C3), 117.3 (2CN), 123.2 (quinoline-C3), 125.7 (Ar–C1), 126.3 (quinoline-C4a), 127.8 (quinoline-C6), 128.1 (quinoline-C8), 128.4 (quinoline-C5), 129.2 (Ar–C2,6), 130.2 (quinoline-C7), 138.3 (quinoline-C4), 142.9 (CH=N), 147.6 (quinoline-C8a), 154.1 (quinoline-C2), 156.7 (pyridine-C6), 160.6 (Ar-C4), 161.9 (C=O, pyridine-C2), 162.3 (pyridine-C4); MS m/z (%) = 455 (M++1, 14.1), 454 (M+, 19.2), 429 (16.2), 419 (15.7), 414 (6.8),398 (15.4), 190 (5.1),189 (15.7), 187 (0.27), 80 (100); Anal. Calcd. for C24H15ClN6O2 (454.87): C, 63.37; H, 3.32; N, 18.48 %, Found: C, 63.34; H, 3.29; N, 18.44 %.

6-Amino-4-(4-chlorophenyl)-1-((2-chloroquinolin-3-yl)methyleneamino)-2-oxo-1,2-dihydropyridine-3,5-dicarbonitrile (9b)

Yellow powder; yield 89 %; mp = 141–142 °C; IR (KBr) υmax/cm−1 = 3,356, 3,240 (NH2), 2,214 (CN), 1,654 (C=O, amidic), 1,559 (C=C, conjugated), 756 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 6.73 (s, 2H, NH2), 7.54 (d, J = 8.5 Hz, 2H, Ar–H2,6), 7.60 (d, J = 8.5 Hz, 2H, Ar–H3,5), 7.62 (t, J = 6.5 Hz, 1H, quinoline-H6), 7.63 (t, J = 6.5 Hz, 1H, quinoline-H7), 7.95 (d, J = 8 Hz, 1H, quinoline-H8), 8.15 (d, J = 8 Hz, 1H, quinoline-H5), 8.75 (s, 1H, CH=N), 9.00 (s, 1H, quinoline-H4); 13C NMR (DMSO-d 6): δppm = 77.4 (pyridine-C5), 116.1 (pyridine-C3), 117.3, 117.6 (2CN), 125.4 (quinoline-C3), 127.5 (quinoline-C4a), 127.8 (quinoline-C6), 128.1 (quinoline-C8), 128.3 (quinoline-C5), 128.6 (Ar–C3,5), 129.4 (Ar–C2,6), 130.5 (Ar–C1), 131.2 (quinoline-C7), 134.3 (Ar–C4), 134.7 (quinoline-C4), 144.8 (CH=N), 148.3 (quinoline-C8a), 153.5 (quinoline-C2), 156.1 (pyridine-C6), 163.8 (C=O, pyridine-C2), 165.9 (pyridine-C4); MS m/z (%) = 458 (M+, 23.9), 394 (16.3), 204 (18.7), 191 (17.5), 190 (3.9), 155 (1.5),111(2.42), 80 (100), 66 (4.2);Anal. Calcd. for C23H12Cl2N6O (459.29): C, 60.15; H, 2.63; N, 18.30 %, Found: C, 60.11; H, 2.60; N, 18.34 %.

6-Amino-1-((2-chloroquinolin-3-yl)methyleneamino)-4-(2,4-difluorophenyl)-2-oxo-1,2-dihydropyridine-3,5-dicarbonitrile (9c)

Red powder; yield 82 %; mp = 115–116 °C; IR (KBr) υmax/cm−1: 3,353, 3,247 (NH2), 2,216 (CN), 1,654 (C=O, amidic), 1,618 (C=N), 1,560 (C=C, conjugated), 756 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 6.75 (s, 2H, NH2), 6.70 (s, 1H, Ar–H3), 6.87 (d, J = 7 Hz, 1H, Ar–H5), 7.20 (d, J = 7 Hz, 1H, Ar–H6), 7.35 (t, J = 7.5 Hz, 1H, quinoline-H7), 7.53 (t, J = 7.5 Hz, 1H, quinoline-H6), 7.70 (d, J = 7 Hz, 1H, quinoline-H8), 7.81 (d, J = 7 Hz, 1H, quinoline-H5), 8.12 (s, 1H, CH=N), 9.00 (s, 1H, quinoline-H4); 13C NMR (DMSO-d 6 ): δppm = 75.4 (pyridine-C5), 109.9 (Ar–C5), 113.7 (Ar–C3), 115.5 (pyridine-C3), 116.3, 116.9 (2CN), 118.1 (Ar–C1), 126.3 (quinoline-C3), 127.5 (quinoline-C4a), 127.7 (quinoline-C6), 128.1 (quinoline-C8), 128.6 (quinoline-C5), 129.4 (Ar–C6), 131.8 (quinoline-C7), 132.4 (quinoline-C4), 141.2 (CH=N), 147.1 (quinoline-C8a), 155.9 (quinoline-C2), 158.5 (Ar–C2), 159.3 (pyridine-C6), 162.3 (Ar–C4), 163.6 (C=O, pyridine-C2), 165.3 (pyridine-C4); MS m/z (%) = 460 (M+, 27.9), 347 (24.3), 190 (0.4), 189 (16.9), 162 (8.8), 161 (3.7), 160 (1.8),159 (22.1), 127 (100), 113 (4.0), 94 (27.94), 80 (87.5); Anal. Calcd. for C23H11ClF2N6O (460.82): C, 59.95; H, 2.41;N, 18.24 %, Found: C, 59.92; H, 2.46;N, 18.20 %.

6-Amino-1-((2-chloroquinolin-3-yl)methyleneamino)-2-oxo-4-(thiophen-2-yl)-1,2-dihydropyridine-3,5-dicarbonitrile (9d)

Orange powder; yield 80 %; mp > 300 °C; IR (KBr) υmax/cm−1 = 3,350, 3,244(NH2), 2,210 (CN), 1,654 (C=O, amidic), 1,610 (C=N), 1,559 (C=C, conjugated), 757(C–Cl); 1H NMR (DMSO-d 6): δppm = 6.96 (s, 2H, NH2), 7.64-8.70 (m, 8H, Ar–H), 8.84 (s, 1H, CH=N); 13C NMR (DMSO-d 6): δppm = 63.6 (pyridine-C5), 117.1, 117.4 (2CN), 120.1 (pyridine-C3), 123.5 (quinoline-C3), 124.3 (quinoline-C4a), 126.1 (thiophen-C3), 127.6 (quinoline-C6), 128.1 (quinoline-C8), 129.2 (quinoline-C5), 129.8 (thiophen-C4), 130.4 (thiophen-C5), 132.2 (quinoline-C7), 134.3 (thiophen-C2), 136.2 (quinoline-C4), 142.0 (CH=N), 145.6 (quinoline-C8a), 151.2 (quinoline-C2), 157.5 (pyridine-C6), 163.8 (C=O, pyridine-C2), 168.3 (pyridine-C4); MS m/z (%) = 430 (M+, 4.4), 348 (9.9), 289 (21.0), 269 (20.3), 268 (10.5), 213 (13.4), 211 (10.2), 162 (17.6), 105 (10.5), 80 (100); Anal. Calcd. for C21H11ClN6OS (430.87): C, 58.54; H, 2.57; N, 19.50 %, Found: C, 58.50; H, 2.53; N, 19.55 %.

General procedure for the synthesis of iminocoumarin derivatives 10a–c

The substituted salicylaldehdye (0.002 mol) was added to a solution of compound 10 (0.79 g, 0.002 mol) in absolute ethanol (30 mL) containing three drops of piperidine. The reaction mixture was heated under reflux for 1 h, then left to cool to room temperature. The precipitate obtained was isolated by filtration, washed with ethanol, dried, and recrystallized from EtOH to afford compounds 10a–c.

N′-((2-Chloroquinolin-3-yl)methylene)-2-imino-2H-chromene-3-carbohydrazide (10a)

Yellow powder; yield 60 %; mp = 225–227 °C; IR (KBr) νmax/cm−1 = 3,354 (NH), 3,228 (NH), 1,662 (C=O, amidic), 1,611 (C=N), 1,583 (C=C, conjugated), 756 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 7.04 (t, J = 8 Hz, 1H, (iminocoumarin-H6), 7.29 (t, J = 8 Hz, 1H, (iminocoumarin-H7), 7.49 (t, J = 8 Hz, 1H, quinoline-H6), 7.56 (d, J = 8.5 Hz, 1H, (iminocoumarin-H8), 7.72 (d, J = 8.5 Hz, 1H, (iminocoumarin-H5), 7.96 (s, 1H, (iminocoumarin-H4), 8.01 (d, J = 7.5 Hz, 1H, quinoline-H8), 8.27 (d, J = 7.5 Hz, 1H, quinoline-H5), 8.58 (s, 1H, quinoline-H4), 8.91 (s, 1H, CH=N), 12.14 (s, 1H, NH), 13.87 (s, 1H, NH, Iminocoumarin); 13C NMR (DMSO-d 6 ): δppm = 109.7 (iminocoumarin-C4a), 115.5 (iminocoumarin-C8), 120.1 (iminocoumarin-C3), 123.5 (iminocoumarin-C6), 125.6 (quinoline-C3), 126.9 (quinoline-C4a), 127.6 (quinoline-C6), 127.9 (quinoline-C8), 129.1 (quinoline-C5), 130.2 (iminocoumarin-C4), 131.9 (iminocoumarin-C5), 133,5 (iminocoumarin-C7), 134.9 (quinoline-C7), 136.2 (quinoline-C4), 144.2 (CH=N), 147.3 (quinoline-C8a), 152.5 (quinoline-C2), 154.7 (iminocoumarin-C8a), 158.5 (iminocoumarin-C2), 162.3 (C=O); MS m/z (%) = 376 (M+, 0.9), 324 (0.8), 307 (100), 257 (1.1), 232 (0.7), 205 (1.7), 204 (3.4), 189 (65.4), 162 (7.4), 145 (62.2), 144 (5.3); Anal. Calcd. for C20H13ClN4O2 (376.79): C, 63.75; H, 3.48; N, 14.87 %, Found: C, 63.71; H, 3.44; N, 14.85 %.

7-Bromo-N′-((2-chloroquinolin-3-yl)methylene)-2-imino-2H-chromene-3-carbohydrazide (10b)

Orange powder; yield 69 %; mp = 198–199 °C; IR (KBr) νmax/cm−1 = 3,354 (NH), 3,284 (NH) 1,654 (C=O, amidic), 1,614 (C=N), 1,599 (C=C, conjugated),750 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 7.72 (t, J = 7 Hz, 1H, quinoline-H6),7.88 (t, J = 7 Hz, 1H, quinoline-H7), 7.96 (s, 1H, (iminocoumarin-H5), 7.98 (d, J = 7.5 Hz, 1H, (iminocoumarin-H4), 8.02 (d, J = 7.5 Hz, 1H, (iminocoumarin-H8), 8.10 (d, J = 8.5 Hz, 1H, quinoline-H8), 8.23 (d, J = 8.5 Hz, 1H, quinoline-H5), 8.45(s, 1H, (iminocoumarin-H8), 8.92 (s, 1H, quinoline-H4), 9.01 (s, 1H, CH=N), 9.36 (s, 1H, NH, Iminocoumarin) 12.13 (s, 1H, NH); 13C NMR (DMSO-d 6 ): δppm = 113.5 (iminocoumarin-C8), 115.9 (iminocoumarin-C4a), 120.9 (iminocoumarin-C3), 125.7 (quinoline-C3), 126.8 (quinoline-C4a), 127.7 (quinoline-C6), 127.9 (quinoline-C8), 128.6 (iminocoumarin-C5), 129.7 (quinoline-C5), 131.6 (iminocoumarin-C4), 131.8 (quinoline-C7), 135.9 (iminocoumarin-C6), 139.4(iminocoumarin-C7), 147.1 (quinoline-C4), 148.2 (CH=N), 152.3 (quinoline-C8a), 155.7 (iminocoumarin-C8a), 162.3 (quinoline-C2), 165.3 (iminocoumarin-C2, C=NH), 168.5 (C=O); MS m/z (%) = 455 (M+, 9.7), 375 (2.2), 265 (2.6), 232 (0.8), 221 (6.4), 205 (4.5), 204 (4.5), 197 (8.9), 196 (3.5), 189 (14.6),169 (100), 162 (4.9); Anal. Calcd. for C20H12BrClN4O2 (455.69): C, 52.71; H, 2.65;N, 12.29 %, Found: C, 52.67; H, 2.61; N, 12.26 %.

N′-((2-Chloroquinolin-3-yl)methylene)-2-imino-7-nitro-2H-chromene-3-carbohydrazide (10c)

Yellow powder; yield 80 %; mp > 300 °C; IR (KBr) νmax/cm−1 = 3,350 (NH), 3,285 (NH), 1,661 (C=O, amidic), 1,613 (C=N), 1,593 (C=C, conjugated), 762 (C–Cl), 1,348–1,529 (NO2); 1H NMR (DMSO-d 6 ): δppm = 7.39 (d, J = 7.5 Hz, 1H, (iminocoumarin-H8), 7.52 (s, 1H, (iminocoumarin-H4), 7.64 (t, J = 7 Hz, 1H, quinoline-H6), 7.70 (s, 1H, (iminocoumarin-H5), 7.85 (t, J = 7 Hz, 1H, quinoline-H7), 8.52 (d, J = 7.5 Hz, 1H, (iminocoumarin-H7), 8.54 (d, J = 8 Hz, 1H, quinoline-H8), 8.65 (d, J = 8 Hz, 1H, quinoline-H5), 8.83 (s, 1H, CH=N), 9.19 (s, 1H, quinoline-H4), 10.24 (s, 1H, NH, Iminocoumarin), 12.23 (s, 1H, NH); 13C NMR (DMSO-d 6 ): δppm = 110.9 (iminocoumarin-C8), 112.7 (Iminocoumarin -C4a), 112.9 (iminocoumarin-C3), 113.1 (quinoline-C3), 113.4 (iminocoumarin-C5), 113.5 (iminocoumarin-C7), 115.0 (quinoline-C4a), 115.4 (quinoline-C6), 115.6 (quinoline-C8), 115.8 (quinoline-C5), 124.7 (iminocoumarin-C4), 125.9 (quinoline-C7), 136.4 (quinoline-C4), 141.1 (iminocoumarin-C6), 143.6 (CH=N), 145.4 (quinoline-C8a), 151.8 (quinoline-C2), 158.1 (Iminocoumarin -C8a), 162.3 (iminocoumarin-C2), 168.5 (C=O); MS m/z (%) = 421(M+, 7.3), 307 (100), 218 (6.1), 204 (3.9), 189 (0.2), 163 (5.9), 162(0.8), 144 (0.2), 128 (16.9); Anal. Calcd. for C20H12ClN5O4 (421.79): C, 56.95; H, 2.87; N, 16.60 %, Found: C, 56.91; H, 2.83; N, 16.57 %.

General procedure for synthesis of coumarin derivatives 11a–c

A solution of compound 10a–c (0.001 mol) in absolute ethanol (15 mL) containing conc. HCl (4 M, 5 mL) was heated under reflux for 1 h. The mixture was left to cool, and the precipitate was isolated by filtration, washed with water, dried, and recrystallized from acetic acid to afford compounds 11a–c.

N′-((2-Oxo-1,2-dihydroquinolin-3-yl)methylene)-2-oxo-2H-chromene-3-carbohydrazide (11a)

Yellow powder; yield 69 %; mp > 300 °C; IR (KBr) νmax/cm−1 = 3,443 (NH), 3,256 (NH), 1,716 (C=O), 1,664, 1,655 (2C=O, amidic), 1,610 (C=N), 1,560 (C=C, conjugated); 1H NMR (CF3COOD): δppm = 7.16 (d, J = 7.5 Hz, 1H, coumarin-H8), 7.18 (t, J = 7 Hz, 1H, coumarin-H6), 7.31 (t, J = 6.5 Hz, 1H, quinoline-H6), 7.39 (d, J = 7.5 Hz, 1H, coumarin-H5), 7.48 (d, J = 8.5 Hz, 1H, quinoline-H8), 7.51 (t, J = 7 Hz, 1H, coumarin-H7), 7.64 (t, J = 6.5 Hz, 1H, quinoline-H7), 7.69 (d, J = 8.5 Hz, 1H, quinoline-H5), 8.59 (s, 1H, CH=N), 8.77 (s, 1H, coumarin-H4), 8.87 (s, 1H, quinoline-H4), 9.8 (s, 1H, NH), 12.66 (s, 1H, NH); 13C NMR (CF3COOD): δppm = 115.4 (coumarin-C3), 115.8 (quinoline-C3), 116.3 (coumarin-C8), 117.3 (coumarin-C4a), 118.6 (coumarin-C4), 122.9 (quinoline-C4a), 123.1 (quinoline-C6), 126.1 (coumarin-C6), 126.8 (coumarin-C8), 127.5 (coumarin-C5), 127.8 (quinoline-C5), 128.6 (coumarin-C7), 130.8 (quinoline-C7), 136.3 (quinoline-C4), 144.2 (CH=N), 149.1 (quinoline-C8a), 153.8 (coumarin-C8a), 160.8 (C=O, coumarin-C2), 167.2 (C=O), 178.5 (quinoline-C2, C=O); MS m/z (%) = 359 (M+, 14.5), 307 (29.0), 214 (3.9), 190 (100), 172 (15.6), 156 (8.4),128 (24.0); Anal. Calcd. for C20H13N3O4 (359.33): C, 66.85; H, 3.65; N, 11.69 %, Found: C, 66.81; H, 3.62; N, 11.66 %.

6-Bromo-N′-((2-oxo-1,2-dihydroquinolin-3-yl)methylene)-2-oxo-2H-chromene-3-carbohydrazide (11b)

Orange powder; yield 71 %; mp > 300 °C; IR (KBr) νmax/cm−1 = 3,448 (NH), 3,258 (NH), 1,717(C=O), 1,670, 1,655 (2C=O, amidic), 1,611 (C=N), 1,559 (C=C, conjugated); 1H NMR (CF3COOD): δppm = 7.35 (d, J = 6.5 Hz, 1H, coumarin-H8), 7.41 (t, J = 7.5 Hz, 1H, quinoline-H6), 7.59 (d, J = 6.5 Hz, 1H, coumarin-H7), 7.63 (t, J = 6.5 Hz, 1H, quinoline-H7), 7.84 (d, J = 8.5 Hz, 1H, quinoline-H8), 8.09 (d, J = 8.5 Hz, 1H, quinoline-H5), 8.26 (s, 1H, coumarin-H5), 8.34 (s, 1H, coumarin-H4), 8.85 (s, 1H, quinoline-H4), 9.07 (s, 1H, CH=N), 10.18 (s, 1H, NH), 12.10 (s, 1H, NH); 13C NMR (CF3COOD): δppm = 113.2 (coumarin-C3), 114.5 (quinoline-C3), 119.4 (coumarin-C8), 119.9 (coumarin-C4), 120.6 (coumarin-C6), 123.9 (quinoline-C4a), 124.2 (coumarin-C4a), 125.0 (quinoline-C6), 127.8 (quinoline-C8), 128.5 (quinoline-C5), 129.9 (coumarin-C5), 130.5 (quinoline-C7), 137.7 (quinoline-C4), 143.8 (CH=N), 149.5 (quinoline-C8a), 152.1 (coumarin-C8a), 157.9 (C=O, coumarin-C2), 165.4 (C=O), 177.2 (quinoline-C2, C=O); MS m/z (%) = 437 (M+, 0.3), 420 (0.2), 251 (100), 223 (6.6), 222 (0.1), 188 (0.2), 171 (0.9), 144 (0.3); Anal. Calcd. for C20H12BrN3O4 (438.23): C, 54.81; H, 2.76; N, 9.59 %, Found: C, 54.78; H, 2.73; N, 9.55 %.

N′-((2-Oxo-1,2-dihydroquinolin-3-yl)methylene)-6-nitro-2-oxo-2H-chromene-3-carbohydrazide (11c)

Yellow powder; yield 97 %; mp > 300 °C; IR (KBr) νmax/cm−1 = 3,422 (NH), 3,256 (NH), 1,724 (C=O), 1,670, 1,654 (2C=O, amidic), 1,618 (C=N), 1,559 (C=C, conjugated), 1,517, 1,346 (NO2); 1H NMR (CF3COOD): δppm = 7.69 (t, J = 7 Hz, 1H, quinoline-H6), 7.98 (t, J = 7 Hz, 1H, quinoline-H7), 8.45 (d, J = 7.5 Hz, 1H, coumarin-H8), 8.47 (d, J = 7.5 Hz, 1H, quinoline-H8), 8.63 (d, J = 7.5 Hz, 1H, quinoline-H5), 8.86 (d, J = 7.5 Hz, 1H, coumarin-H7), 8.90 (s, 1H, coumarin-H4), 9.50 (s, 1H, coumarin-H5), 9.28 (s, 1H, quinoline-H4), 9.32 (s, 1H, CH=N), 10.01 (s, 1H, NH), 10.37 (s, 1H, NH); 13C NMR (CF3COOD): δppm = 115.7 (coumarin-C3), 117.4 (quinoline-C3), 118.6 (coumarin-C8), 119.5 (coumarin-C4), 122.9 (coumarin-C4a), 125.8 (quinoline-C4a), 125.9 (coumarin-C5), 126.2 (coumarin-C7), 127.7 (quinoline-C6), 127.9 (quinoline-C8), 129.6 (quinoline-C5), 132.7 (quinoline-C7), 137.9 (quinoline-C4), 144.3 (CH=N), 146.1 (coumarin-C6), 148.3 (quinoline-C8a), 158.8 (coumarin-C8a), 159.4 (C=O, coumarin-C2), 168.2 (C=O), 180.0 (quinoline-C2, C=O); MS m/z (%) = 404 (M+, 55.2), 218 (55.2), 187 (54.5), 186 (41.0), 172 (54.5), 171 (41.0), 144 (44.8), 121 (52.2), 78 (100), 77 (0.8); Anal. Calcd. for C20H12N4O6 (404.33): C, 59.41; H, 2.99; N, 13.86 %, Found: C, 59.44; H, 2.96; N, 13.82 %.

General procedure for synthesis of arylhydrazone derivatives 12a–c

A cold solution of aryl diazonium salt solution (prepared by addition of a solution of sodium nitrite (0.2 g, 0.025 mol) in water (5 mL) to aromatic amines (0.002 mol) in concentrated HCl (0.5 ml)) was added, in small portions, with stirring, over 30 min, to an ice-cold solution of compound 3 (0.79 g, 0.002 mol) in pyridine (10 mL). The solution was stirred for a further 2 h at 0 °C then diluted with cold water (10 mL). The precipitate formed was isolated by filtration, washed with water, dried well, and recrystallized from 3:1 EtOH–DMF to give compounds 12a–c.

2-(2-((2-Chloroquinolin-3-yl)methylene)-hydrazinyl)-2-oxo-N′-phenylacetohydrazonoyl cyanide (12a)

Orange crystals; yield 99 %; mp = 216–217 °C; IR (KBr) νmax/cm−1 = 3,205, 3,197 (2NH), 2,215 (CN), 1,667 (C=O, amidic), 1,616 (C=N), 1,559 (C=C, conjugated), 751 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 7.27 (t, J = 6.5 Hz, 1H, Ar–H4), 7.30 (d, J = 8 Hz, 2H, Ar–H3,5), 7.40 (d, J = 8 Hz, 2H, Ar–H2,6), 7.48 (t, J = 8 Hz, 1H, quinoline-H6), 7.64 (t, J = 8 Hz, 1H, quinoline-H7), 7.82 (d, J = 7.5 Hz, 1H, quinoline-H8), 7.86 (d, J = 7.5 Hz, 1H, quinoline-H5), 8.60 (s, 1H, quinoline-H4), 9.29 (s, 1H, CH=N), 11.92 (s, 1H, NH-Ar), 12.23 (s, 1H, NH); 13C NMR (DMSO-d 6 ): δppm = 110.9 (C–CN), 113.0 (CN), 113.6 (Ar–C2,6), 124.0 (Ar–C4), 124.8 (quinoline-C3), 125.8 (quinoline-C4a), 125.9 (quinoline-C6), 127.4 (quinoline-C8), 127.6 (quinoline-C5), 128.9 (Ar–C3,5), 129.0 (quinoline-C7), 129.9 (Ar-C1), 142.5 (CH=N), 148.9 (quinoline-C8a), 150.1 (quinoline-C2), 163.9 (C=O); MS m/z (%) = 376 (M+, 19.0), 351 (3.7), 307 (100), 299 (2.8), 274 (14.2), 162 (14.6); Anal. Calcd. for C19H13ClN6O (376.08): C, 60.56; H, 3.48; N, 22.30 %, Found: C, 60.53; H, 3.44; N, 22.27 %.

2-(2-((2-Chloroquinolin-3-yl)methylene)-hydrazinyl)-2-oxo-N′-p-tolylacetohydrazonoyl cyanide (12b)

Orange powder; yield 87 %; mp = 209–210 °C; IR (KBr) νmax/cm−1 = 3,198, 3,101 (2NH), 2,209 (CN), 1,660 (C=O, amidic), 1,615 (C=N), 1,559 (C=C, conjugated),760 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 2.32 (s, 3H, CH3),7.24 (d, J = 8 Hz, 2H, Ar–H2,6), 7.62 (d, J = 8 Hz, 2H, Ar–H3,5), 7.71 (t, J = 7 Hz, 1H, quinoline-H6), 7.88 (t, J = 7 Hz, 1H, quinoline-H7), 8.12 (d, J = 8 Hz, 1H, quinoline-H8), 8.24 (d, J = 8 Hz, 1H, quinoline-H5), 8.45 (s, 1H, quinoline-H4), 9.00 (s, 1H, CH=N), 11.94 (s, 1H, NH-Ar), 12.16 (s, 1H, NH); 13C NMR (DMSO-d 6 ) δppm = 20.5 (CH3), 106.2 (C–CN), 111.3 (CN), 116.4 (Ar–C2,6), 125.7 (quinoline-C8), 126.8 (quinoline-C4a), 127.6 (quinoline-C6), 127.8 (quinoline-C6), 128.6 (quinoline-C5),129.6 (Ar–C3,5),131.8 (quinoline-C7), 131.9(Ar–C4), 135.7(quinoline-C4), 139.6(Ar–C1), 142.9 (CH=N), 148.5 (quinoline-C8a), 159.1 (quinoline-C2), 162.3 (C=O); MS m/z (%) = 390 (M+, 85.4), 324 (60.0), 285 (76.4), 229 (59.1), 228 (52.8), 188 (54.55), 162 (57.3),154 (100); Anal. Calcd. for C20H15ClN6O (390.09): C, 61.46; H, 3.87; N, 21.50 %, Found: C, 61.42; H, 3.84; N, 21.54 %.

2-(2-((2-Chloroquinolin-3-yl)methylene)-hydrazinyl)-N′-(4-methoxyphenyl)-2-oxoacetohydrazonoyl cyanide (12c)

Orange powder; yield 88 %; mp = 181–182 °C; IR (KBr) νmax/cm−1 = 3,208, 3,143 (2NH), 2,213 (CN), 1,664 (C=O, amidic), 1,616 (C=N), 1,559 (C=C, conjugated), 761 (C–Cl); 1H NMR (DMSO-d 6 ): δppm = 3.78 (s, 3H, CH3), 7.01(d, J = 9 Hz, 2H, Ar–H3,5), 7.69 (d, J = 9 Hz, 2H, Ar–H2,6), 7.72 (t, J = 5.5 Hz, 1H, quinoline-H6), 7.86 (t, J = 6 Hz, 1H, quinoline-H7), 8.09 (d, J = 8 Hz, 1H, quinoline-H8), 8.22 (d, J = 8 Hz, 1H, quinoline-H5), 8.61 (s, 1H, quinoline-H4), 8.93(s, 1H, CH=N), 11.90 (s, 1H, N–NH–Ar), 12.22 (s, 1H, NH–C=O); 13C NMR (DMSO-d 6 ) δppm = 55.3 (CH3), 105.3(C–CN), 114.4(CN), 115.9(Ar–C3,5), 117.9 (Ar-C3,5), 125.7 (quinoline-C3), 126.8 (quinoline-C4a), 127.6 (quinoline-C6), 127.8 (quinoline-C8), 127.9 (quinoline-C5), 131.8 (quinoline-C7), 135.6 (Ar-C1), 135.9 (quinoline-C4), 143.0 (CH=N), 148.5 (quinoline-C8a), 156.6 (quinoline-C2), 158.9 (Ar–C4), 162.3 (C=O); MS m/z (%) = 406 (M+, 10.7), 376 (2.62), 375 (0.6), 299 (2.6), 232 (2.6), 205 (4.5), 204 (5.9), 189 (13.3), 162 (8.3), 122 (100); Anal. Calcd. for C20H15ClN6O2(406.09): C, 59.05; H, 3.72; N, 20.66 %, Found: C, 59.01; H, 3.69; N, 20.63 %.

Synthesis of 4-((2-chloroquinolin-3-yl)methyleneamino)-5-oxo-2-phenyl-2,3,4,5-tetrahydro-1,2,4-triazine-6-carbonitrile (13)

To a mixture of compound 12a (0.8 g, 0.002 mol) and formalin (0.06 mL, 0.002 mol) in absolute ethanol (25 mL), piperidine (0.2 mL) was added. The reaction mixture was heated under reflux for 6 h, and then allowed to cool down. The formed precipitate was filtered off, dried and recrystallized from ethanol to give compound 13.

Brown powder; yield 62 %; mp > 300 °C; IR (KBr) νmax/cm−1 = 2,989 (C–H, SP3), 2,212 (CN), 1,701 (C=O), 1,617 (C=N), 1,560 (C=C, conjugated), 760 (C–Cl); 1H NMR (CF3COOD): δppm = 4.50 (s, 2H, CH2), 7.26–7.86 (m, 9H, Aromatic-H), 8.65 (s, 1H, quinoline-H4), 9.70 (s, 1H, CH=N); 13C NMR (CF3COOD): δppm = 76.6 (CH2), 110.7 (CN), 117.5 (Ar–C2,6), 121.7 (Ar–C4), 125.8 (quinoline-C3), 126.7 (quinoline-C6), 127.0 (quinoline-C8), 127.8 (quinoline-C5), 129.5 (Ar–C3,5), 130.3 (quinoline-C7), 136.8 (quinoline-C4), 144.1 (CH=N), 146.4 (Ar–C1), 149.7 (quinoline-C8a), 154.3 (quinoline-C8a), 156.9 (triazine-C6), 163.9 (C=O, triazine-C6); MS m/z (%) = 388 (M+, 45.8), 353 (5.1), 328 (6.8), 311 (44.1), 286 (5.1), 257 (2.5), 251 (100), 233 (69.5), 204 (48.3), 205 (52.5), 190 (16.1); Anal. Calcd. for C20H13ClN6O (388.08): C, 61.78; H, 3.37; N, 21.61 %, Found: C, 61.75; H, 3.33; N, 21.64 %.

Antibacterial screening

Whatman filter paper disks of standard size (6.0 mm diameter) were prepared and placed in 1.0-oz screw-capped wide-mouthed containers for sterilization in a hot air oven at 150 °C. The disks, impregnated with a solution of the test compound in DMSO (100 ml, 5 mg/mL), were then placed on nutrient agar plates seeded with the appropriate test organism. Experiments were performed in triplicate. A standard concentration of 106 CFU/mL (colony-forming units/mL) was used for antibacterial assay.

Pyrex glass Petri dishes (9 cm in diameter) were used, and each plate contained two impregnated filter paper disks. B. subtilis, S. faecalis, and P. aeruginosa were used as examples of Gram-positive bacteria and S. aureus, E. coli, and N. gonorrhoeae as Gram-negative bacteria. Ampicillin was used as standard antibacterial agent. DMSO alone was used as control and resulted in no visible change in bacterial growth. The plates were incubated at 37 °C for 24 h. The mean zone of inhibition was measured in mm.

Anticancer screening

Fetal bovine serum (FBS) and l-glutamine, were from Gibco Invitrogen (Scotland, UK). RPMI-1640 medium was from Cambrex (New Jersey, USA). DMSO was used as solvent and doxorubicin was used as reference anticancer agent. Penicillin, streptomycin, and sulforhodamine B (SRB) were purchased from Sigma Chemical (Saint Louis, USA).

Four human tumor cell lines, breast cancer (MCF-7), non-small cell lung (NCI-H460), central nervous system (SF-268), and lung fibroblasts (WI-38), were obtained from the European Collection of Cell Cultures (ECACC, Salisbury, UK) and National Cancer institute (NCI, Cairo, Egypt).

They were grown as monolayers and routinely maintained in RPMI-1640 medium supplemented with 5 % heat-inactivated FBS, 2 mM glutamine and antibiotics (penicillin 100 U/mL, streptomycin 100 μg/mL), at 37 °C, in a humidified atmosphere containing 5 % CO2.

Exponentially growing cells were obtained by plating 1.5 × 105 cells/mL for MCF-7 and SF-268 and 0.75 × 104 cells/mL for NCI-H460, then incubated for 24 h. The effect of the solvent (DMSO) on the growth of these cell lines was evaluated in all experiments by exposing untreated control cells to the maximum concentration (0.5 %) of DMSO used in each assay.

The effect of the compounds on the in-vitro growth of the cell lines was evaluated in accordance with the procedure adopted by the National Cancer Institute (NCI, USA) and as reported in the publication “In vitro Anticancer Drug Discovery Screen” that uses the protein-binding dye sulforhodamine B to assess cell growth [30, 31]. Briefly, exponentially growing cells in 96-well plates were exposed for 48 h to five serial concentrations of each compound; the maximum concentrations was 150 μM. After this exposure period, adherent cells were fixed, washed, and stained. The bound stain was solubilized and the absorbance was measured at 492 nm by use of a plate reader (PowerWave XS; Bio-Tek Instruments, Winooski, USA). For each test compound and cell line, a dose–response curve was obtained and the concentration which inhibited cell growth by 50 % (IC50) was calculated as described elsewhere. Doxorubicin was used as positive control and was tested in the same manner.