2016 年 64 巻 5 号 p. 439-450
The present work describes convenient synthesis of the novel Schiff bases 5a and b by reacting phthalazinones 4a and b with 4-methoxybenzaldehyde Reaction of the Schiff bases with phenylisothiocyanate afforded diazetidine derivatives 7a and b. Also, compounds 4a and b reacted with 2-bromoglucoside tetraacetate giving peracetylated N-glycosides 6a and b, which were deacetylated to afford N-glycosylated phthalazinones 8a and b. On the other hand, when compound 3 was treated with POCl3/PCl5 and/or ethyl chloroacetate, chlorophthalazine and ethyl acetate derivatives 9 and 10 were obtained, respectively. Hydrazinolysis of compounds 9 and 10 produced the hydrazino and hydrazide derivatives 11 and 12, respectively. When compound 11 reacted with 2-furanaldehyde, acetic anhydride, and/or carbon disulphide, it gave compounds 13–15, respectively. Treatment of the hydrazide 12 with aromatic aldehydes, acetic anhydride, ethyl acetoacetate, acetyl acetone, ammonium thiocyanate, and/or phthalic anhydride furnished compounds 17–21. Meanwhile, reacting Schiff base 22 with the chlorophthalazine derivative 9 produced compound 23, which on treatment with furoyl chloride produced compound 24. The structures of the novel compounds were confirmed by IR, 1H-NMR, 13C-NMR, MS, and elemental analysis. The newly synthesized compounds were tested against Bacillus subtilis and Staphylococcus aureus as Gram-positive bacteria, Escherichia coli and Pseudomonas aurignosa as Gram-negative bacteria, and Candida albicans and Aspergillus niger as fungi strains. Compounds 5a and b, 23, and 24 showed greater antimicrobial activity than the stranded compounds, suggesting that they could be considered as promising antimicrobial agents.
Phthalazines as N-heterocycles have received considerable attention in the literature as a consequence of their role as pharmacophore.1,2) Recently, they are derived from a wide range of biologically active natural products, troponoid family.3) A novel series of N-substituted-4-phenyl/benzylphthalazin-1-ones, phthalzine-1,4-dione showed antitumor activity.4–7) It is well known that phthalazinone derivatives like other members of isomeric diazine series have considerable biological and pharmaceutical activities. Indeed, several phthalazinone derivatives have been reported to possess anti-rheumatic,8) antihyperglycemic,9) anticonvulsant,10) antihypertensive,11) antithrombotic,12) antitrypanosoma,13) antioxidant,14) anti-inflammatory15) and β-adrenergic blocking activities.16) Besides, they can be used as Potent Vasodilators,17) and α1-adrenoceptor antagonists.18) A number of established drug molecules like Hydralazine,19) Azelastine,20) Ponalrestat21) and Zopolrestat22) were prepared from the corresponding phthalazinones. Moreover, many substituted and fused phthalazine and phthalzinone derivatives exhibited antimicrobial activity.23–26)
On the basis of the above findings and in continuation of our research interest in the synthesis of novel biologically active heterocycles,27–31) and with the aim of preparing new derivatives of phthalazine with potential pharmacological activity, we report here the synthesis of novel Schiff bases containing phthalazine moiety, phthalazinone and fused phthalazine derivatives, followed by evaluation of their antimicrobial activity against different strains of bacteria and fungi, where most of synthesized compounds exhibited a moderate to a strong antimicrobial activities. Some of the tested compounds showed antimicrobial activity higher than the reference compounds.
The reaction of commercially available 2-(2-(4-methoxyphenyl)acetyl)benzoic acid (1) with hydroxyl amine and/or hydrazine hydrate, afforded 4-(4-methoxybenzyl)-1H-benzo[d][1,2]oxazin-1-one (2)32) and phthalazinone derivative 3,33,34) respectively. Treatment of 2 with binucleophiles e.g., 1,4-phenylenediamine and 4,4′-diaminobiphenyl afforded the N-substituted phthalazinone derivatives 4a and b, respectively (Chart 1).
Compounds 4a and b may be formed through the nucleophilic attack of the amino group (of the diamine) on the carbonyl group of benzoxazine causing ring opening followed by elimination of water molecule and ring closure. The structure of these compounds were elucidated depending on their IR spectra which displayed peaks in the region 3348–3283 attributable to NH2 groups, and 1H-NMR which showed signals at δ 6.39 (s, 2H, NH2, D2O exchangeable) for 4a and 6.23 (s, 2H, NH2, D2O exchangeable) for 4b, respectively.
When compounds 4a and b were refluxed with 4-methoxybenzaladehyde in absolute ethanol and/or 2-bromo-2-deoxy-1,3,4,6-tetra-O-acetyl-α-D-glucopyranose in dioxane,35) the Schiff bases 5a and b and the N-α-D-glucosetetraacetate phthalazinone derivatives 6a and b were obtained, respectively, in a good yield (Chart 2).
Reagents and conditions: (i) 4-Methoxybenzaldehyde/EtOH/reflux 3 h (74–80%), (ii) 2-bromo-2-deoxy-1,3,4,6-tetra-O-acetyl-α-D-glucopyranose/dioxane/reflux 4 h (56–58%), (iii) PhNCS/toluene/reflux/6 h (68–72%), (iv) Na2CO3 solution/MeOH (43–48%).
Formation of the Schiff bases 5a and b occurs through the nucleophilic attack of the amino on the carbonyl group of the aldehyde followed by elimination of water molecule. The IR spectra of 5a and b devoid any bands for the NH2 group and the mass spectra showed molecular ion peaks at m/z 475 and 551, respectively.
The structure of compounds 6a and b was confirmed from the IR spectra which showed three peaks in the region 1660–1685 attributable to three C=O groups of phthalazinone and peracetyl moieties, respectively. Also, their 1H-NMR spectra displayed signals at δ 2.08–2.29 (s, 12H, 4COCH3), and 2.05–2.24 (s, 12H, 4COCH3), respectively.
When the Schiff bases 5a and b were allowed to react with phenylisothiocyanate, diazetidine derivatives 7a and b were obtained. The proposed structure 7a and b were elucidated from the IR spectra which displayed peaks in the region 1319–1322 attributable to C=S group, 1H-NMR spectra which showed peaks at δ 6.56–6.61 corresponding to the benzylic protons of the diazetidine ring. Also by the mass spectra which showed molecular ion peaks at m/z 610 and 686, respectively.
Moreover, the hydrolysis of 6a and b, using sodium carbonate, afforded the deacetylated glucose phthalazinone derivatives 8a and b35) (Chart 2). The structures of 8a and b were assigned by their IR spectra which displayed peaks at ν (cm−1) 3384–3261 (OH bonded and non-bonded) and mass spectra that showed a molecular ion peaks at m/z 519 and 595, respectively.
On the other hand, the phthalazinone derivative 3 was subjected to react with a mixture of POCl3/PCl536) and/or ethyl chloroacetate, in presences of potassium carbonate,34) producing 1-chlorophthalazine and phthalazinone ethyl acetate derivatives 9 and 10, respectively.
The formation of 9 takes place via the reaction of POCl3/PCl5 with the hydroxyl group of the enol form of compound 3. The structure of 9 was indicated from its IR spectrum which devoid any bands for the C=O and NH groups. While the formation of product 10 is believed to proceed via SN2 mechanism through nucleophilic attack of the lone pair of nitrogen atom on the electronically deficient carbon attached to chlorine atom followed by elimination of HCl molecule. The structure of 10 was confirmed as a result of the presence of two absorption bands at 1745, 1684 (in the IR spectra) attributable to two C=O groups of the ethyl ester and phthalazinone moieties. Also, the 1H-NMR showed δ 1.34 (t, 3H, CH3, J=6.1 Hz) and 4.39 (q, 2H, CH2, J=8.2 Hz), indicating the presence of ethyl ester group.
When both compounds 9 and 10 were further reacted with hydrazine hydrate in boiling ethanol, the hydrazino phthalazine37) and phthalazinone acetohydrazide34) derivatives 11 and 12 were produced, respectively (Chart 3).
Reagents and conditions: (i) POCl3/PCl5/reflux 4 h (84%), (ii) ClCH2CO2C2H5/K2CO3/dry acetone/reflux 24 h (80%), (iii) N2H4·H2O/EtOH/reflux 3 h (85, 90%).
Formation of compound 11 takes place through nucleophlic attack of hydrazine molecule on the carbon atom (attached to the chlorine atom) followed by elimination of HCl molecule. The IR spectrum of 11 showed peaks at 3379, 3285, 3147 (NH2, NH).
On the other hand, the hydrazide 12 is formed via tetrahedral mechanism through the attacking of nucleophilic hydrazine molecule on the sp2 carbon of the carbonyl functionality of the ester group in compound 10 with the elimination of an ethanol molecule. The structure of hydrazide 12 was supported by its spectroscopic data, where the IR spectrum displayed peaks at 3350, 3211, 3130 (NH2, NH) and the 1H-NMR indicated the absence of any peaks for the ethyl group.
The 1-hydrazinophthalazine derivative 11 was used as a key starting material to synthesize different interesting phthalazine and fused phthalazine derivatives. Thus, condensation of 11 with 2-furanaldehyde in boiling ethanol, produced the hydrazone derivative 13.38) While, 1,2,4-triazolo[3,4-a]-phthalazines 14, and 15 have been prepared upon the reaction of 11 with carbon electrophiles namely, acetic anhydride and carbon disulphide, respectively.
Compound 13 is formed through condensation reaction between the carbonyl group of the aldehyde and the amino group of the hydrazino-derivative. The IR spectrum of 13 devoid any peaks for the NH2 group, and the 1H-NMR showed a peak at δ 6.39 for the methine proton (–N=CH–).
A plausible explanation for the formation of product 14 consists in acetylation of the hydrazino group followed by 1,3-proton shift, attacking of lone pair of N-1 on the acetyl carbonyl group and finally elimination of a water molecule. The structure was elucidated by the spectroscopic data, where the IR showed the absence of any absorption bands for NH or NH2, and the 1H-NMR showed a peak at δ 2.44 (s, 3H), corresponding to the methyl group.
Compound 15 is possibly formed through the attacking of the nucleophilic amino group on the electronically deficient carbon of carbon disulfide, 1,3-proton shift then attacking of N-1 on C=S functionality with the elimination of H2S molecule. The IR spectrum of 15 showed a peak at 1271 (C=S) and devoid any bands for NH and NH2 groups. Also the 1H-NMR displayed a peak at δ 11.96 (s, 1H, D2O exchangeable) attributable to the SH group.
Compound 15 was confirmed chemically via its reaction with hydrazine hydrate to furnish the corresponding hydrazine derivative 16 (Chart 4).
Reagents and conditions: (i) 2-Furanaldehyde/EtOH/reflux 3 h (76%), (ii) Ac2O/heat 1 h (62%), (iii) CS2/KOH/abs. EtOH/reflux 6 h (60%), (iv) N2H4·H2O/EtOH/reflux 3 h (54%).
Compound 16 may take place by the nucleophilic attack of the hydrazine molecule on the carbon atom (bearing the SH group), followed by elimination of H2S molecule. The structure of 16 gets support from its spectroscopic data which showed absorption bands (ν cm−1) at 3364, 3260, 3174 attributable to both NH and NH2 and δ values (ppm) at 5.65 (s, 2H, NH2, D2O exchangeable) and 11.11 (s, 1H, NH, D2O exchangeable).
Meanwhile, the hydrazide 12 could be used as versatile synthon for preparing different hydrazones and building up many ring systems by reacting the hydrazide group with different reagents. Thus, reaction of 12 with different aldehydes such as furan-2-carboxaldehyde, piperonal and 2-methoxybenzaldehyde, in boiling ethanol, gave the hydrazones 17a–c,39) respectively. This reaction takes place through a condensation reaction between the NH2 group of hydrazide 12 and the carbonyl group of the aldehyde. The structures of hydrazones 17a–c were supported by the their IR spectra which devoid any peaks for the NH2 group, and the 1H-NMR spectra which displayed peaks at δ 6.16–6.31 (s, 1H) for the methine proton N=CH–.
Reaction of 12 with acetic anhydride and/or ethyl acetoacetate afforded the 1,3,4-oxadiazole derivatives 18a and b, respectively.
According to our speculation, product 18a is formed through actylation of the hydrazine group of compound 12, 1,3-proton shift followed by cyclization with the elimination of a water molecule. The IR spectrum of this compound devoid any peaks for NH and NH2 groups and its 1H-NMR spectrum showed a peak at δ 2.55 (s, 3H) attributable to the methyl group. While compound 18b is believed to be formed through nucleophilic attack of the amino group on the electronically deficient carbonyl carbon of the ester group with elimination of EtOH molecule, 1,3-proton shift and finally cyclization with elimination of water molecule. The structure of 18b was elucidated from its IR spectrum which displayed absorption bands at 1672, 1660 for two C=O groups, and the 1H-NMR spectrum which showed peaks at δ 2.01 (s, 3H), for –COCH3 and 3.92 (s, 2H) for –CH2–CO– of the acetonyl group.
On the other hand, treatment of 12 with acetyl acetone and/or ammonium thiocyanate in ethanol, produced pyrazole and 1,3,4-triazole derivatives 19 and 20, respectively. The 1,3-dioxoisoindoline derivative 21 was obtained upon fusion of the hydrazide 12 with phthalic anhydride in an oil bath at 170°C (Chart 5).
Reagents and conditions: (i) Ar′CHO/EtOH/reflux 3 h (74–85%), (ii) Ac2O and/or CH3COH2CO2Et/EtOH/reflux 4 h (69–77%), (iii) CH3COCH2COCH3/EtOH/reflux 3 h (71%), (iv) NH4SCN/EtOH/reflux 3 h (61%), (v) phthalic anhydride/fusion at 170°C/for 1 h (58%).
Product 19 may be formed as a result of a condensation process between the hydrazide moiety of compound 12 and a molecule of acetyl acetone followed by cyclization of the lactim form (of the condensation product) with elimination of water molecule. The presence of two bands for two C=O groups in the IR spectrum of compound 19 supported its proposed structure. Also, its 1H-NMR displayed peaks at δ 2.12 (s, 3H) for the COCH3 group, 2.79 (s, 3H) for the methyl group attached to the pyrazole ring and 3.89 (s, 1H, pyrazole).
It is well known that ammonium thiocyanate isomerizes to thiourea under the effect of heat.40) So, the mercaptotriazole 20 could be obtained from the attacking of thiourea on the carbonyl of the hydrazide moiety followed by cyclization as a result of elimination of ammonia molecule. The structure of compound 20 was confirmed by the IR spectrum which showed a band at 1265 (C=S) and the 1H-NMR spectrum which displayed two peaks at 10.76, 12.22, (2s, 2H, D2O exchangeable) corresponding to NH and SH, respectively.
On the other hand, compound 21 is formed as a result of nucleaophilic attack of the amino group on one of the carbonyl functionalities of phthalic anhydride accompanied by the cleavage of the five memberd ring then cyclization with the elimination of water molecule to form the 1,3-dioxoisoindoline ring. The structure of 21 was elucidated depending the IR spectrum which indicated the presence of four absorption bands at 1770, 1742, 1680, 1660 (CO). Also, the mass spectrum showed a molecular ion peak at m/z 468 (14.2%).
When Dapson (4,4′-sulfonyldianiline) was reacted with 4-methoxyacetophenone in equimolar amount, the mono imino-compound 22 was obtained in fair yield. It should be noted that there is a possibility for the formation of di-iminated compound, but we isolated only the mono-derivative, where the IR of the product showed bands at 3430 and 3321 (NH2). This may be attributed to the use of only one mole of 4-methoxyacetophenone.
Compound 22 was allowed to react with 1-chlorophthalazine derivative 9 in the presence of pyridine, producing the phthalazine derivative 23 through the nucleophilic attack of the amino group on the carbon atom (bearing chlorine atom) followed by elimination of HCl molecule. The IR of 23 showed only on absorption band at 3230 attributable to the NH group.
Reaction of 23 with 2-furoyl chloride, in dry pyridine, afforded the phthalazine derivative 24 (Chart 6), whose structure was inferred by the IR spectrum which exhibited a strong peak at 1674 attributable to the C=O group attached to the furoyl moiety and the mass spectrum which showed a molecular ion peak at m/z 722 (25.7%).
Reagents and conditions: (i) 4-Methoxyacetophenone/EtOH/reflux 4 h (63%), (ii) compound 9/ethanol/drops of pyridine/relux 6 h (58%), iii) 2-furoyl chloride/dry pyridine/reflux 3 h (78%).
Compound 24 was formed via tetrahedral mechanism through the attacking of the lone pair of the NH group of 23 on the sp2 carbon of the carbonyl functionality of furoyl chloride, followed by elimination of HCl molecule.
Antimicrobial ActivityThe antimicrobial screening of the synthesized compounds has been evaluated by using agar diffusion method according to Cheesbrough.41) The synthesized compounds have been tested for their antibacterial activity against Bacillus subtilis (ATCC-6633), Staphylococcus aureus (ATCC-25923), Escherichia coli (ATCC-25922) and Pseudomonas aeruginosa (ATCC-9027), and antifungal activity against Candida albicans (ATCC-24433), Aspergillus niger (ATCC-16404), at a concentration of 100 µg/mL in dimethyl sulfoxide (DMSO). Nutrient agar and potato dextrose agars were used to culture the bacteria and fungi, respectively. The plates were inculcated by the bacteria or fungi and incubated for 24 h at 37°C for bacteria and for 72 h at 28°C for fungi and then the inhibition zones of microbial growth surrounding the filter paper disc (5 mm) were measured in millimeters. Ampicillin and Nystatin, at a concentration 100 µg/mL, were used as standard against bacteria and fungi, respectively. The obtained results are compiled in Table 1.
| Cmpd No. | Antibacterial activity (mm) | Antifungal activity (mm) | ||||
| Gram-positive bacteria | Gram-negative bacteria | Candida albicans | Aspergillus niger | |||
| Bacillus subtilis | Staphylococcus aureus | Escherichia coli | Pseudomonas aeruginosa | |||
| 3 | 17 | 14 | 13 | 14 | 16 | 13 |
| 4a | 14 | 13 | 11 | 10 | 12 | 10 |
| 4b | 13 | 10 | 12 | 12 | 14 | 11 |
| 5a | 27 | 26 | 22 | 22 | 24 | 20 |
| 5b | 28 | 26 | 21 | 20 | 23 | 18 |
| 6a | 20 | 17 | 14 | 15 | 17 | 13 |
| 6b | 17 | 16 | 13 | 14 | 14 | 11 |
| 7a | 16 | 18 | 17 | 17 | 14 | 12 |
| 7b | 18 | 17 | 16 | 18 | 19 | 15 |
| 8a | 22 | 19 | 18 | 16 | 16 | 11 |
| 8b | 19 | 18 | 15 | 13 | 14 | 12 |
| 9 | 14 | 12 | 10 | 10 | 15 | 13 |
| 10 | 17 | 15 | 12 | 11 | 15 | 10 |
| 11 | 11 | 14 | 10 | 12 | 11 | 12 |
| 12 | 23 | 21 | 18 | 18 | 20 | 17 |
| 13 | 19 | 16 | 16 | 13 | 18 | 15 |
| 14 | 15 | 14 | 12 | 12 | 10 | 11 |
| 15 | 19 | 17 | 14 | 15 | 11 | 11 |
| 16 | 16 | 18 | 17 | 19 | 15 | 14 |
| 17a | 23 | 20 | 18 | 15 | 17 | 13 |
| 17b | 22 | 20 | 19 | 18 | 18 | 15 |
| 17c | 18 | 19 | 16 | 13 | 10 | 11 |
| 18a | 17 | 18 | 18 | 15 | 16 | 14 |
| 18b | 18 | 16 | 14 | 17 | 15 | 11 |
| 19 | 21 | 18 | 15 | 14 | 12 | 16 |
| 20 | 22 | 20 | 17 | 18 | 19 | 15 |
| 21 | 16 | 19 | 17 | 17 | 15 | 12 |
| 23 | 28 | 25 | 22 | 21 | 23 | 21 |
| 24 | 26 | 24 | 22 | 20 | 24 | 19 |
| Ampicillin | 25 | 22 | 20 | 19 | — | — |
| Nystatin | — | — | — | — | 22 | 18 |
Cmpd No: compound number; mm: millimeter.
From the above table, it is clear that most of the compounds have moderate to strong antimicrobial activity. Compounds 5a, b, 23 and 24 showed antimicrobial activity higher than the standard compounds, which means that they could be considered as promising antimicrobial agents.
The minimum inhibition concentration for the most potent compounds are recorded in Table 2 using the two fold dilution method.
| Cmpd No. | Gram-positive bacteria | Gram-negative bacteria | Fungi | |||
| Bacillus subtilis | Staphylococcus aureus | Escherichia coli | Pseudomonas aeruginosa | Candida albicans | Aspergillus niger | |
| 5a | 12.5 | 12.5 | 50 | 50 | 25 | 50 |
| 5b | 12.5 | 12.5 | 50 | 50 | 25 | 50 |
| 23 | 12.5 | 25 | 50 | 50 | 25 | 50 |
| 24 | 12.5 | 25 | 50 | 50 | 25 | 50 |
The inhibitory capability of the most active compounds (5a, b, 23 and 24) was demonstrated in Figs. 1A and B. These potent compounds showed higher activity against Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) compared with Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). On the other hand less activity was showed against both fungal strains Candida albicans and Aspergillus niger.
B. s.: Bacillus subtilis; S. a.: Staphylococcus aureus; E. c.: Escherichia coli; P. s.: Pseudomonas aeruginosa; C. a.: Candida albicans and A. n.: Aspergillus niger. Nys: nystatin; Amp: ampicillin.
All melting points are uncorrected and were determined on a Gallen Kamp electric melting point apparatus. The microanalyses were within ±0.4% of theoretical values and were carried out at the Microanalytical Centre, National Research Centre, Cairo, Egypt. IR spectra (in KBr) were recorded on Shimadzu FT-IR 8101 PC using the OMNIC program and are reported as frequency of absorption in cm−1. 1H-NMR spectra were recorded on a Bruker spectrophotometer at 400 MHz using tetramethylsilane (TMS) as internal standard. 13C-NMR spectra were recorded on the same spectrometer at 100 MHz. Electron Ionization (EI)-MS were measured on a Shimadzu-GC-MS-QP-1000 EX mass spectrometer instrument operating at 70 eV. The purity of the new synthesized compounds was checked by 0.2 mm layer thickness Fluka aluminum-backed TLC plates with detection by UV quenching at 254 nm. Biological evaluation was carried out at Microbiology Department, Ain Shams University, Faculty of Science, Ain Shams University, Cairo, Egypt. Reagents and solvents were used as obtained from the supplier without further purification.
4-(4-Methoxybenzyl)phthalazin-1(2H)-one (3)This compound was previously prepared by Olmo et al.,33) but no spectroscopic data or chemical analysis was recorded in their paper for this compound. Herein, this compound was prepared according to different previously reported methodology.34)
Yield 93%. mp 254–256°C. IR (KBr), ν cm−1: 3199 (NH), 1661(CO), 1610 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 3.69 (s, 3H, OCH3), 4.22 (s, 2H, CH2Ar), 7.33–8.34 (m, 4H, ArH), 12.74 (s, 1H, NH, D2O exchangeable). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 35.13, 55.79, 113.39, 122.51, 126.15, 127.36, 128.56, 130.23, 132.19, 133.62, 153.44, 154.33, 156.09, 163.14. MS: m/z 266 [M+·] (100%). Anal. Calcd for C16H14N2O2 (266): C, 72.18; H, 5.26; N, 10.52. Found: C, 72.49; H, 5.09; N, 10.90.
General Procedure for the Synthesis of the Phthalazinones 4a and bA mixture of 4-(4-methoxybenzyl)-1H-benzo[d][1,2]oxazin-1-one (2) (2.67 g, 0.01 mol) and 1,4-phenylene diamine, and/or 4,4′-benzidine (0.01 mol) was heated under reflux in absolute ethanol (20 mL) for 6 h. The resulting mixture was cooled and then poured onto an ice/water mixture. The separated solid was filtered, washed with water, air-dried and crystallized from ethanol.
2-(4-Aminophenyl)-4-(4-methoxybenzyl)phthalazin-1(2H)-one (4a)Yield 76%. mp 168–170°C. IR (KBr), ν (cm−1): 3348, 3287 (NH2), 1665 (C=O), 1619 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 3.70 (s, 3H, OCH3), 4.23 (s, 2H, CH2Bz), 6.39 (s, 2H, NH2, D2O exchangeable), 7.18–8.26 (m, 12 H, ArH). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 35.01, 56.22, 114.51, 120.81, 122.51, 126.68, 127.31, 128.72, 129.62, 130.18, 131.18, 133.41, 146.92, 147.58, 154.01, 156.02, 158.12, 162.90. MS: m/z 357 [M+·] (27.9). Anal. Calcd for C22H19N3O2 (357): C, 73.95; H, 5.32; N, 11.76. Found: C, 74.31; H, 5.54; N, 12.05.
2-(4′-Amino-[1,1′-biphenyl]-4-yl)-4-(4-methoxybenzyl)phthalazin-1(2H)-one (4b)Yield 68%. mp 182–184°C. IR (KBr), ν (cm−1): 3339, 3283 (NH2), 1669 (C=O), 1622 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 3.74 (s, 3H, OCH3), 4.25 (s, 2H, CH2Bz), 6.23 (s, 2H, NH2), 7.08–8.19 (m, 16H, ArH). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 35.42, 54.91, 114.41, 120.82, 122.01, 122.99, 125.11, 126.72, 127.32, 128.69, 130.21, 131.01, 132.12, 133.39, 134.78, 137.21, 140.11, 146.89, 150.01, 154.09, 156.58, 162.81. MS: m/z 433 [M+] (35.7). Anal. Calcd for C28H23N3O2 (433): C, 77.60; H, 5.31; N, 9.70. Found: C, 77.44; H, 5.04; N, 10.02.
General Procedure for the Synthesis of the Schiff Bases 5a and bA mixture of compounds 4a and b (0.01 mol) and 4-methoxybenzaldehyde (1.36 g, 0.01 mol) was heated under reflux in absolute ethanol (20 mL) for 3 h. The resulting mixture was cooled and then poured onto an ice/water mixture. The separated solid was filtered, washed with water, dried and then crystallized from ethanol.
4-(4-Methoxybenzyl)-2-(4-((4-methoxybenzylidene)amino)phenyl)phthalazin-1(2H)-one (5a)Yield 80%. mp 200–202°C: IR (KBr), ν (cm−1): 1668 (C=O), 1615 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 3.65, 3.78 (2s, 6H, 2OCH3), 4.22 (s, 2 H, CH2Bz), 6.68 (s, 1H, =CH–), 7.18–8.19 (m, 16 H, ArH). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 35.23, 54.89, 55.12, 116.49, 120.81, 122.51, 126.59, 127.31, 129.22, 130.44, 132.04, 133.19, 134.39, 136.55, 140.81, 142.51, 146.59, 148.68, 149.31, 151.72, 153.59, 155.62, 158.18, 164.92. MS: m/z 475 [M+] (40%). Anal. Calcd for C30H25N3O3 (475): C, 75.79; H, 5.26; N, 8.84. Found: C, 76.16; H, 5.00; N, 8.55.
4-(4-Methoxybenzyl)-2-(4′-((3-methoxybenzylidene)amino)-[1,1′-biphenyl]-4-yl)phthalazin-1(2H)-one (5b)Yield 74%. mp 212–214°C. IR (KBr), ν (cm−1): 1667 (C=O), 1617 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 3.62, 3.79 (2s, 6H, 2OCH3), 4.19 (s, 2H, CH2Bz), 6.75 (s, 1H,=CH–); 7.24–8.22 (m, 20H, ArH). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 35.77, 54.96, 55.80, 116.41, 119.19, 120.62, 122.69, 123.87, 125.11, 126.19, 126.72, 127.32, 128.69, 130.21, 131.01, 132.12, 133.39, 134.42, 135.78, 136.44, 137.21, 138.88, 140.11, 146.89, 150.01, 154.00, 158.54, 165.58. MS: m/z 551 [M+] (35.7%). Anal. Calcd for C36H29N3O3 (551): C, 78.40; H, 5.26; N, 7.62. Found: C, 78.07; H, 5.00; N, 7.29.
Synthesis of 1,3-Diazetidine Derivatives 7a and bEquimolar amounts of 5a and b (0.01 mol) and phenyl isothiocyanate (1.35 g, 0.01 mol) in 25 mL toluene was refluxed for 6 h. The solvent was distilled off and the residue was washed with ethanol followed by water, and the product was crystallized from ethanol.
4-(4-Methoxybenzyl)-2-(4-(2-(4-methoxyphenyl)-3-phenyl-4-thioxo-1,3-diazetidin-1-yl)phenyl)-phthalazin-1(2H)-one (7a)Yield 68%. mp 278–280°C. IR (KBr), ν (cm−1): 1664 (C=O), 1614 (C=N), 1319 (C=S). 1H-NMR (400 MHz, DMSO-d6) δ: 3.61, 3.76 (2s, 6H, 2 OCH3), 4.21 (s, 2H; CH2Bz), 6.56 (s, 1H, benzylic H), 7.15–8.20 (m, 21H, ArH). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 35.33, 55.44, 56.05, 95.46, 115.91, 116.19, 120.62, 122.69, 126.67, 128.23, 128.89, 129.73, 130.32, 130.91, 131.91, 132.21, 133.66, 134.40, 135.66, 136.41, 137.03, 137.79, 141.14, 144.87, 153.23, 154.55, 158.89, 166.67, 174.21. MS: m/z 610 [M+] (59.1%): Anal. Calcd for C37H30N4O3S (610): C, 72.79; H, 4.92; N, 9.18; S, 5.25. Found: C, 73.15; H, 5.21; N, 9.55; S, 5.63.
4-(4-Methoxybenzyl)-2-(4′-(2-(4-methoxyphenyl)-3-phenyl-4-thioxo-1,3-diazetidin-1-yl)-[1,1′-biphenyl]-4-yl)phthalazin-1(2H)-one (7b)Yield 72%. mp 284–286°C. IR (KBr), ν (cm−1): 1671 (C=O), 1522 (C=N), 1322 (C=S). 1H-NMR (400 MHz, DMSO-d6) δ: 3.64, 3.73 (2s, 6H, 2 OCH3), 4.24 (s, 2H; CH2Bz), 6.61 (s, 1H, benzylic H), 7.13–8.25 (m, 25H, ArH). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 35.45, 55.23, 55.89, 96.12, 115.78, 117.02, 121.82, 122.56, 126.88, 127.49, 128.12, 128.78, 129.33, 129.81, 130.24, 130.98, 131.66, 132.29, 133.69, 134.51, 135.72, 136.32, 137.22, 138.12, 138.82, 139.39, 140.51, 141.32, 142.67, 152.88, 154.34, 159.61, 165.58, 174.99. MS: m/z 686 [M+] (66.3%). Anal. Calcd for C43H34N4O3S (686): C, 75.22; H, 4.96; N, 8.16; S, 4.67. Found: C, 74.90; H, 5.23; N, 7.88; S, 5.00.
Synthesis of Acetylated Derivatives 6a and b and Deacetylated Derivatives 8a and bA mixture of phthalazinones 2a and b (0.01 mol) and 2-bromo-2-deoxy-1,3,4,6-tetra-O-acetyl-α-D-glucopyranose (4.1 g, 0.01 mol) in 100 mL 1,4-dioxane was heated with frequent stirring under reflux for 4 h. The mixture was cooled to room temperature and the solvent was removed under reduced pressure. The residue was dissolved in ethyl acetate, washed sequentially with saturated NaHCO3 (3×20 mL), then with water and dried over MgSO4. The purification and separation was achieved by column chromatography (EtOAc–hexane, 3 : 1) giving the acetylated products 6a and b as a white solid which was later on recrystallized using diethyl ether–hexane as a solvent. A solution of 6a and b in MeOH (50 mL) was treated with sodium carbonate solution (2.12 g, 0.05 mol in 20 mL water). After stirring for 30 min, a white solid syrupy began to settle. The residue was then purified by column chromatography (EtOAc–hexane, 3 : 1) giving the deacetylated derivatives each as a white solid, which was crystallized by dichloromethane–diethyl ether as a solvent, affording 8a and b, respectively.
6-(Acetoxymethyl)-3-((4-(4-(4-methoxybenzyl)-1-oxophthalazin-2(1H)-yl)phenyl)amino)-tetrahydro-2H-pyran-2,4,5-triyl Triacetate (6a)Yield 58%. mp 124–126°C. IR (KBr), ν (cm−1): 3334 (NH); 1685, 1671, 1660 (C=O), 1H-NMR (400 MHz, DMSO-d6) δ: 2.08–2.29 (s, 12H, 4 COCH3), 3.65 (s, 3H, OCH3), 4.18 (s, 2H, CH2Bz), 4.32–5.87 (m, 7H, CH2OAc and pyran-H), 7.18–8.28 (m, 12H, ArH), 11.03 (s, 1H, NH, D2O exchangeable). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 22.02, 22.81, 36.11, 55.37, 61.39, 70.89, 71.91, 72.38, 73.10, 92.89, 115.44, 118.89, 121.11, 122.42, 126.59, 127.32, 128.42, 130.38, 131.11, 132.42, 136.59, 136.71, 143.19, 146.90, 154.01, 160.58, 171.20, 174.21, MS: m/z [M+] 687 (1.4%). Anal. Calcd for C36H37N3O11 (687): C, 62.88; H, 5.39; N, 6.11. Found: C, 63.24; H, 5.08; N, 5.78.
6-(Acetoxymethyl)-3-((4′-(4-(4-methoxybenzyl)-1-oxophthalazin-2(1H)-yl)-[1,1′-biphenyl]-4-yl)amino)tetrahydro-2H-pyran-2,4,5-triyl Triacetate (6b)Yield 56%. mp 164–166°C. IR (KBr), ν (cm−1): 3311 (NH); 1683, 1673, 1662 (C=O), 1H-NMR (400 MHz, DMSO-d6) δ: 2.05–2.24 (s, 12H, 4 COCH3), 3.68 (s, 3H, OCH3), 4.24 (s, 2H, CH2Bz), 4.34–5.84 (m, 7H, CH2OAc and pyran-H), 7.22–8.24 (m, 16H, ArH), 10.89 (s, 1H, NH, D2O exchangeable). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 21.82, 23.01, 35.89, 55.90, 61.01, 70.22, 71.39, 72.54, 74.45, 88.21, 114.89, 115.55, 120.78, 122.01, 125.11, 126.59, 127.72, 128.29, 130.22, 131.43, 132.62, 133.41, 134.38, 137.20, 140.78, 142.01, 145.11, 146.72, 154.00, 160.59, 172.20, 173.92. MS: m/z 763 [M+] (10.9%). Anal. Calcd for C42H41N3O11 (763): C, 66.06; H, 5.37; N, 5.50. Found: C, 66.43; H, 5.70; N, 5.16.
4-(4-Methoxybenzyl)-2-(4-((2,4,5-trihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-3-yl)amino)-phenyl)phthalazin-1(2H)-one (8a)Yield 48%. mp 158–160°C. IR (KBr), ν (cm−1): 3384, 3278 (OH bonded and non-bonded), 3185 (NH), 1664 (C=O). 1H-NMR (400 MHz, DMSO-d6) δ: 3.20–3.61 (m, 6H, glucose-H), 3.78 (s, 3H, OCH3), 4.15 (s, 2H, CH2Bz), 4.28, 4.44, 4.59, 4.74 (s, 4H, 4OH of glucose, D2O exchangeable), 5.21 (d, 1H, Hanom, J=7.9 Hz), 7.13–8.31 (m, 12H, Ar-H), 9.37 (s, 1H, NH, D2O exchangeable). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 35.01, 55.99, 61.87, 63.89, 70.21, 73.38, 74.11, 94.62, 115.34, 116.88, 121.11, 124.44, 128.61, 129.70, 130.89, 131.52, 131.78, 132.05, 132.57, 135.39, 144.18, 153.90, 156.03, 160.59. MS: m/z 519 [M+] (25.2%). Anal. Calcd for C28H29N3O7 (519): C, 64.74; H, 5.59; N, 8.09. Found: C, 65.09; H, 5.81; N, 8.43.
4-(4-Methoxybenzyl)-2-(4′-((2,4,5-trihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-3-yl)amino)-[1,1′-biphenyl]-4-yl)phthalazin-1(2H)-one (8b)Yield 43%. mp 188–190°C. IR (KBr), ν (cm−1): 3379, 3261, (OH bonded and non-bonded), 3191 (NH), 1669 (C=O). 1H-NMR (400 MHz, DMSO-d6) δ: 3.23–3.66 (m, 6H, glucose-H), 3.82 (s, 3H, OCH3), 4.10 (s, 2H, CH2Bz), 4.33, 4.51, 4.66, 4.79 (s, 4H, 4OH of glucose, D2O exchangeable), 5.32 (d, 1H, Hanom, J=8.3 Hz), 7.09–8.41 (m, 16H, Ar-H), 9.88 (s, 1H, NH, D2O exchangeable). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 35.47, 56.23, 60.99, 64.12, 71.87, 74.81, 75.43, 95.59, 114.91, 116.64, 121.52, 122.79, 124.78, 126.23, 127.83, 128.57, 129.54, 130.58, 131.33, 131.97, 132.21, 132.88, 134.41, 137.39, 138.68, 154.48, 156.87, 161.24. MS: m/z 595 [M+] (34.2%). Anal. Calcd for C34H33N3O7 (595): C, 68.57; H, 5.55; N, 7.06. Found: C, 68.89; H, 5.84; N, 6.73.
Synthesis of 1-Chloro-4-(4-methoxybenzyl)phthalazine (9)Compound 3 (2.66 g, 0.01 mol) was added to a mixture of 5 mL POCl3 and 2g PCl5. The reaction mixture was refluxed for 4 h, then poured drop wise of ice/water mixture with vigorous stirring. The precipitate so formed was filtered of, washed with water several times, dried then recrystallized from ethanol.
Yield 84%. mp 155–157°C. IR (KBr), ν (cm−1): 3059–2993 (CH), 1610 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 3.66 (s, 3H, OCH3), 4.27 (s, 2H, CH2Bz), 7.12–8.09 (m, 8H, ArH). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 35.59, 56.33, 115.53, 124.19, 125.34, 126.86, 127.76, 128.89, 130.11, 132.34, 133.73, 154.32, 156.31, 159.03. MS: m/z 284 [M]+ (28.9%), 286 [M+2] (10.1%). Anal. Calcd for C16H13N2OCl (284): C, 67.61; H, 4.58; N, 9.86; Cl, 12.50. Found: C, 67.93; H, 4.31; N, 10.23, Cl, 12.12.
Synthesis of Ethyl-2-(4-(4-methoxybenzyl)-1-oxo-phthalazin-2-yl)acetate (10)A mixture of phthalazinone derivative 3 (2.66 g, 0.01 mol), ethylchloroacetate (2.44 g, 0.02 mol) and anhydrous potassium carbonate (5.52 g, 0.04 mol) in dry acetone (50 mL) was refluxed for 24 h. The excess solvent was then removed by distillation and the residue was diluted with water. The obtained solid was filtered off and crystallized from benzene.
Yield 80%. mp 102–104°C. IR (KBr), ν (cm−1): 3042–2885 (CH), 1745, 1684 (CO), 1614 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 1.34 (t, 3H, CH3, J=6.1 Hz), 3.71 (s, 3H, OCH3), 4.21 (s, 2H, CH2Ar), 4.39 (q, 2H, CH2, J=8.2 Hz), 5.1 (s, 2H, NCH2CO), 7.17–7.99 (m, 8H, ArH). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 15.19, 36.11, 51.21, 56.09, 63.22, 115.67, 123.89, 125.56, 126.77, 127.59, 129.09, 130.32, 131.92, 133.45, 153.99, 156.82, 159.79, 171.01. MS: m/z 352 [M+·] (100%). Anal. Calcd for C20H20N2O4 (352): C 68.18, H 5.68, N 7.95. Found: C 67.85, H 5.40, N 8.32.
Synthesis of 1-Hydrazinyl-4-(4-methoxybenzyl)phthalazine (11)A solution of 9 (2.84 g, 0.01 mol) and hydrazine hydrate (0.5 mL; 0.01 mol) in ethanol (30 mL) was heated under reflux for 3 h. The solid that separated after cooling was filtered off and recrystallized from ethanol.
Yield 90%. mp 194–196°C. IR (KBr) ν (cm−1): 3379, 3285, 3147 (NH2, NH), 3048–2864 (CH), 1618 (C=N), 1H-NMR (400 MHz, DMSO-d6) δ: 3.73 (s, 3H, OCH3), 4.28 (s, 2H, CH2Ar), 6.34 (s, 2H, NH2, D2O exchangeable), 7.16–7.91 (m, 8H, ArH), 9.19 (s, 1H, NH, D2O exchangeable). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 36.96, 54.55, 115.97, 118.34, 121.12, 124.41, 127.44, 129.66, 130.54, 131.71, 133.11, 150.03, 156.82, 160.56. MS: m/z 280 [M+·] (43.6%). Anal. Calcd for C16H16N4O (280): C, 68.57; H, 5.71; N 20.00. Found, C, 68.94; H, 6.05; N, 19.68.
Synthesis of 2-(4-(4-Methoxybenzyl)-1-oxophthalazin-2-yl)acetohydrazide (12)A solution of ester 10 (3.52g, 0.01 mol) and hydrazine hydrate (1.0 mL, 0.02 mol) in ethanol (30 mL) was refluxed for 3 h. The reaction mixture was concentrated and the obtained solid was filtered off and recrystallized from ethanol.
Yield 85%. mp 252–254°C. IR (KBr) ν (cm−1): 3350, 3211, 3130 (NH2, NH), 3050–2879 (CH), 1666, 1651 (CO), 1614 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 3.63 (s, 3H, OCH3), 4.14 (s, 2H, CH2Ar), 4.68 (s, 2H, CH2CO), 5.55 (br s, 2H, NH2, D2O exchangeable), 7.21–7.98 (m, 8H, ArH), 10.13 (1H, NH, D2O exchangeable). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 36.43, 56.33, 58.61, 116.27, 124.02, 125.88, 127.12, 128.34, 129.45, 130.72, 131.77, 133.32, 134.21, 152.87, 155.15, 159.02, 172.25. MS: m/z 338 [M+·] (29.6%). Anal. Calcd for C18H18N4O3 (338): C, 63.91; H 5.32; N, 16.57. Found: C, 64.22; H, 5.03; N, 16.20.
Synthesis of 1-(2-(Furan-2-ylmethylene)hydrazinyl)-4-(4-methoxybenzyl)phthalazine (13)A solution of 11 (2.8 g, 0.01 mol) and furfural (0.96 g, 0.01 mol) in ethanol (20 mL) was heated under reflux for 3 h. The solid that separated after cooling was filtered off and recrystallized from ethanol. Yield 76%. mp 140–142°C. IR (KBr) ν (cm−1): 3190 (NH), 3055–2878 (CH), 1614 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 3.63 (s, 3H, OCH3), 4.18 (s, 2H, CH2Ar), 6.39 (s, 1H, –N=CH–), 6.51 (m, 2H, H3, H4-furan) 7.13–8.10 (m, 9H, H5-fur +ArH), 10.77 (s, 1H, NH, D2O exchangeable). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 37.05, 54.09, 111.71, 113.21, 115.22, 117.39, 121.89, 123.79, 128.11, 129.41, 130.30, 131.96, 133.11, 134.67, 142.55, 150.03, 151.62, 156.21, 162.99. MS: m/z 358 [M+·] (22.8%). Anal. Calcd for C21H18N4O2 (358): C, 70.39; H, 5.03; N, 15.64. Found: C, 70.69; H, 5.28; N, 13.00.
Synthesis of 6-(4-Methoxybenzyl)-3-methyl-[1,2,4]triazolo[3,4-a]phthalazine (14)A mixture of 11 (2.8 g, 0.01 mol) and acetic anhydride (10 mL) was heated for one hour on a water bath. Excess acetic anhydride was distilled of and solid was washed with water several times, then recrystallized from ethanol.
Yield 62%. mp 162–164°C. IR (KBr) ν (cm−1): 3052–2891 (CH), 1614 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 2.44 (s, 3H, CH3), 3.65 (s, 3H, OCH3), 4.23 (s, 2H, CH2Ar), 7.12–8.18 (m, 8H, ArH). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 14.44, 36.18, 55.01, 113.21, 123.43, 124.93, 127.34, 128.89, 129.76, 130.44, 131.71, 133.53, 134.67, 148.21, 156.21, 158.86. MS: m/z 304 [M+·] (19.9%). Anal. Calcd for C18H16N4O (304): C, 71.05; H, 5.26; N, 18.42. Found: C, 70.76; H, 5.02; N, 18.70.
Synthesis of 6-(4-Methoxybenzyl)-[1,2,4]triazolo[3,4-a]phthalazine-3-thiol (15)A mixture of 11 (2.8 g, 0.01 mol), carbon disulfide (3.8 g, 0.05 mol) and anhydrous potassium hydroxide (0.5 g) in absolute ethanol (20 mL) was refluxed on a water bath for 6 h. The reaction mixture after cooling and concentration was poured into crushed ice. The solid that separated out was filtered off and recrystallized from dioxane.
Yield 60%. mp 144–146°C. IR (KBr) ν (cm−1): 3039–2874 (CH), 1614 (C=N), 1271 (C=S). 1H-NMR (400 MHz, DMSO-d6) δ: 3.62 (s, 3H, OCH3), 4.26 (s, 2H, CH2Ar), 7.13–8.09 (m, 8H, ArH), 11.96 (s, 1H, SH, D2O exchangeable). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 35.98, 54.89, 115.00, 123.73, 124.69, 127.03, 128.71, 129.18, 130.19, 132.09, 133.48, 149.31, 155.89, 158.18, 160.86. MS: m/z 322 [M+·] (19.9%). Anal. Calcd for C17H14N4OS (322): C, 63.35; H, 4.35; N, 17.39; S, 9.94. Found: C, 63.70; H, 4.08; N, 17.75; S, 10.30.
Synthesis of 3-Hydrazinyl-6-(4-methoxybenzyl)-[1,2,4]triazolo[3,4-a]phthalazine (16)Hydrazine hydrate (1 mL, 0.02 mol) was added to a solution of 15 (3.22 g, 0.01 mol) in 25 mL ethanol. The reaction mixture was heated under reflux for 3 h. The solid that separated after cooling and concentration was filtered off and recrystallized from ethanol.
Yield 54%. mp 168–170°C. IR (KBr) ν (cm−1): 3364, 3260, 3174 (NH2, NH), 3057–2891 (CH), 1614 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 3.66 (s, 3H, OCH3), 4.24 (s, 2H, CH2Ar), 5.65 (s, 2H, NH2, D2O exchangeable), 7.05–8.06 (m, 8H, ArH), 11.11 (s, 1H, NH, D2O exchangeable). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 35.21, 55.44, 115.55, 123.61, 124.18, 127.44, 128.65, 129.39, 130.21, 132.00, 133.66, 148.21, 156.56, 158.45, 159.98. MS: m/z 320 [M+·] (30.2%). Anal. Calcd for C17H16N6O (320): C, 63.75; H, 5.00; N, 26.25. Found: C, 64.02; H, 5.29; N, 25.90.
Synthesis of the Hydrazones 17a–cA solution of acetohydrazide 12 (3.38 g, 0.01 mol) and aromatic aldehydes namely, furan-2-carboxaldehyde, piperonal and 2-methoxybenzaldehyde (0.01 mol) in ethanol (30 mL) was refluxed for 3 h. The reaction mixture allowed to cool and the obtained solid was filtered off and recrystallized from suitable solvent.
N′-(Furan-2-ylmethylene)-2-(4-(4-methoxybenzyl)-1-oxophthalazin-2(1H)-yl)acetohydrazide (17a)Yield 74%. mp 180–182°C. Solvent (benzene). IR (KBr) ν (cm−1): 3170 (NH), 3041–2896 (CH), 1680, 1662 (CO), 1614 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 3.72 (s, 3H, OCH3), 4.27 (s, 2H, CH2Ar), 5.02 (s, 2H, CH2C=O), 6.16 (s, 1H, N=CH), 6.48–6.77 (m, 2H, furH), 7.07–8.13 (m, 9H, ArH and C5-furan-H), 9.99 (s, 1H, NH, D2O exchangeable). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 35.66, 54.44, 58.89, 109.25, 113.33, 117.28, 122.84, 127.09, 128.11, 129.66, 130.57, 131.98, 133.23, 134.71, 138.43, 146.09, 148.23, 152.56, 156.21, 159.88, 168.99. MS: m/z 416 [M+·] (13.5%). Anal. Calcd for C23H20N4O4 (416): C, 66.35; H, 4.81; N, 13.46. Found: C, 66.01; H, 5.06; N, 13.74.
N′-(Benzo[d]1,3-dioxo-5-ylmethylene-2-(4-(4-methoxybenzyl)-1-oxophthalazin-2(1H)-yl)acetohydrazide (17b)Yield 85%. mp 186–188°C. Solvent (ethanol). IR (KBr) ν (cm−1): 3186 (NH), 3052–2890 (CH), 1676, 1665 (CO), 1611 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 3.79 (s, 3H, OCH3), 4.22 (s, 2H, CH2Ar), 5.11 (s, 2H, CH2C=O), 5.63(s, 2H, O–CH2–O), 6.25 (s, 1H, N=CH), 7.14–8.18 (m, 11H, ArH), 10.11 (s, 1H, NH, D2O exchangeable). MS: m/z 470 [M+·] (41.6%). Anal. Calcd for C26H22N4O5 (470): C, 66.38; H, 4.68; N, 11.91. Found: C, 66.07; H, 4.97; N, 12.25.
2-(4-(4-Methoxybenzyl)-1-oxophthalazin-2(1H)-yl)-N′-(2-methoxybenzylidene)acetohydrazide (17c)Yield 82%. mp 192–194°C. Solvent (toluene). IR (KBr) ν (cm−1): 3191 (NH), 3058–2895 (CH), 1679, 1660 (CO), 1618 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 3.62, 3.79 (s, 6H, 2OCH3), 4.14 (s, 2H, CH2Ar), 5.06 (s, 2H, CH2C=O), 6.31 (s, 1H, N=CH), 7.10–8.08 (m, 12H, ArH), 10.32 (s, 1H, NH, D2O exchangeable). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 35.66, 54.44, 56.36, 59.04, 113.45, 115.22, 117.39, 122.76, 124.52, 127.23, 128.65, 129.81, 130.42, 131.78, 132.56, 133.19, 133.89, 134.37, 147.27, 153.42, 154.56, 156.18, 159.23, 169.58. MS: m/z 456 [M+·] (32.8%). Anal. Calcd for C26H24N4O4 (456): C, 68.42; H, 5.26; N, 12.28. Found: C, 68.09; H, 5.00; N, 12.60.
Synthesis of Compounds 18a and bA solution of 12 (3.38 g, 0.01 mol) and acetic anhydride or ethyl acetoacetate (0.01 mol) in ethanol (30 mL) was refluxed for 4 h. The reaction mixture allowed to cool and the obtained solid was filtered off and crystallized from suitable solvent.
4-(4-Methoxybenzyl)-2-((5-methy-1,3,5-oxadiazol-2-yl)methyl)phthalazin-1(2H)-one (18a)Yield 77%. mp 172–174°C. Solvent (benzene). IR (KBr) ν (cm−1): 3044–2876 (CH), 1672 (CO), 1619 (C=N). 1H-NMR spectrum (400 MHz, DMSO-d6) δ: 2.55 (s, 3H, CH3), 3.73 (s, 3H, OCH3), 4.14 (s, 2H, CH2Ar), 4.64 (s, 2H, CH2), 7.07–8.23 (m, 8H, ArH). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 22.06, 35.32, 50.44, 56.11, 113.31, 122.22, 125.66, 128.32, 129.14, 130.59, 131.85, 132.77, 134.37, 154.39, 156.55, 159.23, 161.19, 165.87. MS: m/z 362 [M+·] (29.9%). Anal. Calcd for C20H18N4O3 (362): C, 66.30; H, 4.97; N, 15.47. Found: C, 66.00; H, 5.21; N, 15.16.
Synthesis of 4-(4-Methoxybenzyl)-2-((5-(2-oxopropyl)-1,3,5-oxadiazol-2-yl)methyl)phthalazin-1(2H)-one (18b)Yield 69%. mp 188–190°C. Solvent (dioxane). IR (KBr) ν (cm−1): 3050–2885 (CH), 1672, 1660 (CO), 1614 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 2.01 (s, 3H, COCH3), 3.74 (s, 3H, OCH3), 3.92 (s, 2H, CH2C=O), 4.11 (s, 2H, CH2Ar), 4.69 (s, 2H, CH2), 7.07–8.23 (m, 8H, ArH). MS: m/z 404 [M+·] (18.7%). Anal. Calcd for C22H20N4O4 (404): C, 65.35; H, 4.95; N, 13.86. Found: C, 65.71; H, 5.17; N, 14.14.
Synthesis of 2-((4-Acetyl-5-methyl-4H-pyrazol-3-yl)methyl)-4-(4-methoxybenzyl)-phthalazin-1(2H)-one (19)A solution of 12 (3.38 g, 0.01 mol) and acetyl acetone (1.5 g, 0.015 mol) in ethanol (30 mL) was heated under reflux for 3 h. The reaction mixture allowed to cool and the obtained solid was filtered off and crystallized from ethanol.
Yield 71%. mp 178–180°C. IR (KBr) ν (cm−1): 3051–2893 (CH), 1675, 1663 (CO), 1620 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 2.12 (s, 3H, COCH3), 2.79 (s, 3H, CH3), 3.66 (s, 3H, OCH3), 3.89 (s, 1H, pyrazole), 4.17 (s, 2H, CH2Ar), 4.71 (s, 2H, CH2), 7.10–8.26 (m, 8H, ArH). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 15.06, 27.32, 35.86, 50.21, 53.34, 56.76, 115.01, 122.88, 125.76, 128.44, 129.21, 130.34, 131.96, 132.89, 134.76, 144.99, 154.23, 156.12, 159.14, 161.19, 198.01. MS: m/z 402 [M+·] (16.9%). Anal. Calcd for C23H22N4O3 (402): C, 68.66; H, 5.47; N, 13.93. Found: C, 68.93; H, 5.70; N 14.29.
Synthesis of 2-((5-Mercapto-4H-1,2,4-triazol-3-yl)methyl)-4-(4-methoxybenzyl)phthalazin-1(2H)-one (20)A solution of 12 (3.38 g, 0.01 mol) and ammonium thiocyanate (2.28 g, 0.03 mol) in ethanol (30 mL) was heated under reflux for 3 h. The solid that separated out after cooling was filtered off and crystallized from benzene.
Yield 61%. mp 218–220°C. IR (KBr) ν (cm−1): 3179 (NH), 3061–2892 (CH), 1678 (CO), 1614 (C=N), 1265 (C=S). 1H-NMR (400 MHz, DMSO-d6) δ: 3.75 (s, 3H, OCH3), 4.14 (s, 2H, CH2Ar), 4.57 (s, 2H, CH2), 7.04–8.22 (m, 8H, ArH), 10.76, 12.22, (2s, 2H, NH and, SH D2O exchangeable). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 36.21, 50.29, 56.76, 115.76, 122.69, 125.91, 128.66, 129.01, 130.43, 131.78, 132.89, 134.59, 153.55, 154.45, 156.66, 158.34, 159.14. MS: m/z 379 [M+·] (10.4%). Anal. Calcd for C19H17N5O2S (379): C, 60.16; H, 4.49; N, 18.47; S, 8.44. Found: C, 60.50; H, 4.21; N, 18.09; S, 8.10.
Synthesis of N-(1,3-Dioxoisoindolin-2-yl)-2-(4-(4-methoxybenzyl)-1-oxophthalazin-2(1H)-yl)-acetamide (21)A mixture of hydrazide 12 (3.38 g, 0.01 mol) and phthalic anhydride (1.5 g, 0.01 mol) was heated in an oil bath at 170°C for 1 h. The reaction mixture was allowed to cool and the solid obtained was crystallized from ethanol.
Yield 58%. mp 262–264°C. IR (KBr) ν (cm−1): 3182 (NH), 3051–2880 (CH), 1770, 1742, 1680, 1660 (CO), 1614 (C=N). 1H-NMR (400 MHz, DMSO-d6) δ: 3.62 (s, 3H, OCH3), 4.11 (s, 2H, CH2Ar), 4.59 (s, 2H, CH2), 7.07–8.27 (m, 12H, ArH), 12.23 (s, 1H, NH, D2O exchangeable). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 35.74, 54.34, 58.71, 115.54, 122.99, 124.02, 125.69, 127.11, 128.71, 129.12, 130.66, 131.65, 132.77, 133.44, 134.34, 152.79, 154.32, 156.43, 158.88, 168.11. MS: m/z 468 [M+·] (14.2%). Anal. Calcd for C26H20N4O5 (468): C, 66.67; H, 4.27; N, 11.97. Found: C, 66.34; H, 4.02; N, 12.31.
Synthesis of 4-((4-((1-(4-Methoxyphenyl)ethylidene)amino)phenyl)sulfonyl)aniline (22)A mixture of dapsone (4,4′-sulfonyldianiline) (2.48 g, 0.01 mol) and 4-methoxyacetophenone (1.50 g, 0.01 mol) in 25 mL absolute ethanol was heated under reflux for 4 h. The solid that separated out on cooling was filtered and crystallized from ethanol.
Yield 63%. mp 176–178°C: IR (KBr) ν (cm−1): 3430, 3321 (NH2), 1610 (C=N), 1160 (S=O). 1H-NMR (400 MHz, DMSO-d6) δ: 2.11 (s, 3H, CH3), 3.74 (s, 3H, OCH3), 6.45 (s, 2H, NH2, D2O exchangeable), 7.10–8.11 (m, 12H, 3 ArH). MS: m/z 380 [M+] (33.3%). Anal. Calcd for C21H20N2O3S (380): C, 66.32; H, 5.26; N, 7.37; S, 8.42. Found: C, 66.66; H, 5.55; N, 7.06; S, 8.07.
Synthesis of 4-(4-Methoxybenzyl)-N-(4-((4-((1-(4-methoxyphenyl)ethylidene)amino)phenyl)-sulfonyl)phenyl)phthalazin-1-amine (23)Chlorophthalazine derivative 9 (2.84g, 0.01 mol) and the Schiff base 22 (3.80 g, 0.01 mol) were dissolved in 30 mL absolute ethanol and 0.5 mL pyridine was added. The reaction mixture was heated under reflux for 6 h. The resulting mixture was cooled and poured onto ice/water. The solid that separated out was filtered, washed with water, air-dried and crystallized from ethanol .
Yield 58%. mp 270–272°C: IR (KBr) ν (cm−1): 3230 (NH), 1619 (C=N), 1155 (S=O). 1H-NMR (400 MHz, DMSO-d6) δ: 2.17 (s, 3H, CH3), 3.67, 3.84 (2s, 6H, 2OCH3), 4.21 (s, 2H, CH2Ar), 7.09–8.08 (m, 20H, Ar-H), 9.94 (s, 1H, NH, D2O exchangeable). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 22.79, 36.46, 55.11, 57.52, 113.89, 114.12, 115.33, 117.52, 120.87, 123.31, 124.19, 127.49, 128.99, 129.62, 130.51, 131.68, 132.23, 132.75, 133.43, 135.32, 136.32, 138.7, 144.83, 147.64, 153.91, 155.29, 163.88, 165.22, 167.31. MS: m/z 628 [M+] (13.2%). Anal. Calcd for C37H32N4O4S (628): C, 70.70; H, 5.10; N, 8.91; S, 5.10. Found: C, 71.01; H, 5.37; N, 9.32; S, 5.43.
Synthesis of N-(4-(4-Methoxybenzyl)phthalazin-1-yl)-N-(4-((4-((1-(4-methoxyphenyl)-ethylidene)amino)phenyl)sulfonyl)phenyl)furan-2-carboxamide (24)A mixture of compound 23 (3.14 g, 0.005 mol) and 2-furoyl chloride (0.65 g, 0.005 mol) was refluxed in 30 mL of dry pyridine for 3h. The excess solvent was distilled off and the reaction solution was cooled, then poured into crushed ice with frequent stirring leaving a crude product which was filtered off, washed with water, dried and crystallized from ethanol.
Yield 78%. mp 284–286°C. IR (KBr) ν (cm−1): 1674 (C=O), 1602 (C=N), 1157 (S=O). 1H-NMR (400 MHz, DMSO-d6) δ: 2.14 (s, 3H, CH3), 3.70, 3.85 (2s, 6H, 2OCH3), 4.16 (s, 2H, CH2Ar), 6.82-8.23 (m, 23H, ArH and furan-H). 13C-NMR (100 MHz, DMSO-d6) δ ppm: 22.48, 36.05, 55.82, 58.49, 112.62, 113.45, 114.78, 116.56, 117.72, 120.61, 122.24, 123.60, 124.29, 125.91, 127.48, 128.58, 129.87, 130.25, 131.54, 132.33, 132.89, 134.67, 136.34, 140.78, 142.78, 146.31, 147.42, 149.24, 153.89, 156.32, 158.68, 161.78, 163.31, 166.39. MS: m/z 722 [M+] (25.7%). Anal. Calcd for C42H34N4O6S (722): C, 69.81; H, 4.71; N, 7.76; S 4.43. Found: C, 70.14; H, 5.00; N, 8.08; S, 4.09.
In this paper, several new heterocyclic compounds that contain a phthalazine and phthalazinone moieties were synthesized using simple methods. The structures of the newly synthesized compounds were elucidated by different spectral methods and they were tested for their antimicrobial activities. Most of these compounds showed promising activities against different bacteria and fungi strains.
The authors would like to express their deep appreciation for Prof. Dr. Abd-El-Galil Amr, Pharmaceutical Chemistry Department, College of Pharmacy, King Saud University, Saudi Arabia for his efforts in doing 13C-NMR.
The authors declare no conflict of interest.
