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Synthesis of Novel Series of Phthalazine Derivatives As Potential Antitumor Agents

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Synthesis of Novel Series of Phthalazine Derivatives As Potential Antitumor Agents View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by International Institute for Science, Technology and Education (IISTE): E-Journals Chemical and Process Engineering Research www.iiste.org ISSN 2224-7467 (Paper) ISSN 2225-0913 (Online) Vol.10, 2013 Synthesis of Novel Series of Phthalazine Derivatives as Potential Antitumor Agents Ashraf Farouk Wasfy *, Aly Abdelmaboud Aly, Mohamed Sayed Behalo, Nora Sobhi Mohamed Chemistry department, Faculty of science, Benha University Benha, Egypt. P.O. Box 13518 Tel.: +2.010.1599607Fax: +2.013.3222578 E-mail address: [email protected] (Nora Sobhi) e-mail: [email protected] Abstract: A novel series of phthalazine derivatives bearing isoindol-1,3-dione moiety were synthesized by treating 2-[4-(4- chlorophthalazine-1-yl)phenyl]-1H-isoindole-1,3-(2 H)-dione 3 with various chemical reagents.The newly synthesi- zed compounds were characterized on the basis of their spectral ( 1H NMR, 13 C NMR, Ms, IR) analyses. In vitro , most of the synthesized derivatives were screened for their antitumor activity against HepG2 cells using MTT assay. Compounds 11, 18 and 19c showed the most potent cytotoxic effect concluded from their IC 50 values 217.4, 240.3 and 234.5 µg/ml respectively. Key Words: Phthalazin-1-(2 H)-One; chlorophthalazine; isoindol-1,3-dione; antitumor activity. 1. Introduction: Nitrogen-containing heterocycles possesses diverse chemotherapeutic activities [1,2] . Among a large variety of nitrogen-containing heterocyclic compounds, phthalazin-1(2 H)-ones, they were reported to be used as efficient antitumors [3] and therapeutic agents [4] . N-(4-Chlorophenyl)-4-(pyridin-4-ylmethyl)phthalazin-1- amine, also known as Vatalanib has been shown to serve as anticancer agent (Fig.1) . On the other hand, phthalazinones bearing a substituent at C-4 represent key intermediates in the synthesis of various compounds with highly interesting clinical applications and pharmacological properties, such as anti-heart disease [5] , blood platelet aggregation inhibitors and cardiovascular antihypertensive agents [6-13]. Cl 16 O O 14 10 11 Cl 1N HN N 4 6 8 N O 9' OH 17 N Cl 1' 6' 3' 10' N OH Vatalanib (1) Azamerone (2) Fig. 1 Structures of Vatalanib and Azamerone. Furthermore, meroterpenoid Azamerone, isolated from the saline culture of a new marine-derived bacterium related to the genus Streptomyces represents example of this unique phthalazinone ring system as a natural product (Fig.1) . In addition, a number phthalazinone derivatives are well known to be active as potential anticonvulsant [14] , cardiotonic [15] , vasorelaxant [16] , also used as anticancer agents and antitumor activity [17] . 20 Chemical and Process Engineering Research www.iiste.org ISSN 2224-7467 (Paper) ISSN 2225-0913 (Online) Vol.10, 2013 In view of the above mentioned facts and in continuation of our research interest for the synthesis of biologically active heterocycles [18-20] , we report here, the synthesis of novel series of phthalazinones bearing isoindol-1,3-dione moiety followed by evaluation of their antitumor activities against HepG2 cells using MTT Cell Viability. 2. Results and Discussion: Synthesis of 2-[4-(4-oxo-3,4-dihydrophthalazin-1-yl)phenyl]-1H-isoindo- le-1,3-(2 H)-dione 2 required as starting material was accomplished in high yield by fusion of phthalic anhydride with 4-(4-aminophenyl)- phthalazin-1- (2 H)- one 1 (prepared from the reaction of γ-keto acids with hydrazine hydrate in ethanol [21-23] ) (Scheme 1 ) .The structure of phthalazinone 2 was elucidated on the basis of spectral studies. 1H NMR spectrum showed signal at δ 7.99 ppm corresponding to NH proton, 13.20 corresponding to OH proton exchangeable with D2O, 7.40-7.93 ppm(m,12H, aromatic protons). Also, IR spectrum displayed absorption bands at ύ 3208-3085 cm -1, 1746 – 1700 cm -1, 1685 cm -1 due to NH↔OH, CO imidic, CO amidic, respectively. (Scheme 1 ) O O Fussion H2N O + O N O for 2hrs N NH NN O (1) O H (2) O POCl3 / PCl5 Ar = N Cl O N N Ar (3) Scheme 1 Treatment of phthalazinone 2 with phosphorus pentachloride and phosphorus oxychloride afforded 2- [4-(4-chlorophthalazin-1-yl)phenyl]-1H- isoindole-1,3(2 H)-dione 3 which is used as a reactive key precursor for the synthesis of phthalazine series and their fused derivatives. Thus, the reaction of chlorophthalazine 3 with sodium methoxide furnish- ed 2-[4-(4- methoxyphthalazine-1-yl)-phenyl]isoindole-1,3-dione 4.However, treatment of chlorophthalazine 3 with sodium azide in DMSO afforded tetrazolo phthalazine 5, spectral data and elemental analysis confirmed the proposed structures.On the other hand, the reaction of chlorophthalazine 3 with ethanolamine in dioxane gave product 6 which in turn reacted with SOCl 2 in benzene to give phthalazinium chloride 7. The corresponding free base 8 was formed by treating of compound 7 with 15% K 2CO 3 solution. Furthermore, reaction of chlorophthalazine 3 with thiourea in sodium ethoxide afforded phthalazine derivative 9. (Scheme 2) 21 Chemical and Process Engineering Research www.iiste.org ISSN 2224-7467 (Paper) ISSN 2225-0913 (Online) Vol.10, 2013 O C H 3 CH 3 O N a N CH 3 OH N A r ( 4 ) N N N N a N 3 N ( 3 ) DMSO N A r ( 5 ) NHCH 2 CH 2 OH HN N HOCH 2 CH 2 NH 2 N N 1 0 % K C O N S O C l 2 C l 2 3 D i o x a n e N N N A r ( 6 ) ( 7 ) A r A r SH S ( 8 ) H 2 N C NH 2 N Ehanol/ sod. ethoxide N A r ( 9 ) Scheme (2) Formation of phthalazine 9 possibly proceeded according to mechanism described in Fig.2 . NH NH Cl HS C NH2 SC NH2 NH N Cl + HS C - H NH Cl N NH2 N + H Ar Ar Ar S SH NH NH N Cl C NH2 + N N Ar Ar Fig. 2 Mechanism of the formation of compound 9 Also, refluxing of chlorophthalazine 3 with benzoylhydrazine in butanol furnished 2-[4-(3-phenyl- [1,2,4]triazolo[3,4-a]phthalazine-6-yl)-phenyl]-iso- indole-1,3-dione 10 . The reactivity of chlorophthalazine towards amino acids was also investigated .Thus; treatment of chlorophthalazine 3 with glycine in the presence of pyridine gave acid derivative 11. 1H NMR of acid 11 showed signals at 12.8 and 8.3 corresponding to OH and NH, respectively, singlet at 2.5 ppm corresponding to CH 2. However, the latter compound underwent ring closure by refluxing with acetic anhydride to afford 2-[4-(3-oxo-2,3-dihydro-imidazo[2,1-a ]phthalazine-6-yl)- phenyl]-isoindole-1,3-dione 12 . (Scheme 3) 22 Chemical and Process Engineering Research www.iiste.org ISSN 2224-7467 (Paper) ISSN 2225-0913 (Online) Vol.10, 2013 N N CONHNH C H 2 N 6 5 n-b u tano l N A r (3) (1 0) N NHCH 2COOH O NH 2CH 2 COOH N A c 2 O N P y rid ine N N A r A r (11 ) (12) Scheme 3 On the other hand, anthranilic acid reacted with chlorophthalazine 3 to give tetracyclic system 13 . Whereas, m-amino benzoic acid and p-amino benzoic acid reacted with chlorophthalazine under the same reaction conditions to afford aminophthalazine derivatives 14a,b respectively. Also, chlorophthalazine 3 was refluxed with aromatic amines such as o-phenylenediamine, p-phenylene diamine, o-aminophenol and p- aminophenol in benzene to afford phthalazine derivatives 15a-d respectively. On the other hand, compounds 15a and 15c underwent thermal cyclization to furnish imidazophthalazine derivative 16 . (Scheme 4) . O A r HO C N H 2 N N O N A r (1 3 ) RNH N (3 ) 2 N 1 4 R a C 6 H 4 .C O O H (m ) NHR b C 6 H 4 .C O O H (p ) (1 4 a,b ) A r A r N N RNH 2 B en ze n e N N NHR N (1 5 a -d ) (1 6 ) 1 5 R a C 6H 4 .N H 2 (o ) b C 6H 4 .N H 2 (p ) c C 6H 4 . O H (o) d C H . O H (p ) 6 4 Scheme 4 However, reaction of chlorophthalazine 3 with ammonium thiocyanate lead to formation of 17 which in turn reacted with ethyl isocyanate in dry acetone to give 2-[4-(2-ethyl-1-oxo-3-thioxo-2,3-dihydro-1H- 2,4,10,10a-tetraza- phenanthren-9-yl)-phenyl]-isoindole-1,3-dione 18 . Reactivity of chlorophthal- azine 3 towards primary amines namely, benzylamine, p-amino benzophenone and hydrazine hydrate in n-butanol afforded products 19a-c, respectively. (Scheme 5) . 23 Chemical and Process Engineering Research www.iiste.org ISSN 2224-7467 (Paper) ISSN 2225-0913 (Online) Vol.10, 2013 NCS S E t NH 4 SCN N E t N C O N N dry acetone N N O A r N ( 3 ) ( 1 7 ) A r ( 1 8 ) A r A r N CH COOH N RNH 2 3 N b u t a n o l N CH 3 NHR N ( 1 9 a - c ) ( 2 0 ) p h C H O 1 5 R a A r -CH 2 C 6 H 5 N b -C 6 H 4 COC 6 H 5 - N H N c 2 HNNC H ( 2 1 ) Scheme 5 Furthermore, boiling of hydrazide 19c with acetic acid afforded imidazophthalazine derivative 20 . Finally, refluxing of 19c with benzaldehyde in butanol lead to the formation of benzylidene hydrazone 21 .
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