Pyrazolo phthalazine

Furthermore, pyrazole 366 reacts with phthalazine (Scheme 132) to afford pyrazolo[3, 4 4,5]pyrido[6,l-a]phthalazine (367). From a mechanistic viewpoint, no 1,6-dipolar cyclization occurs. Instead, an intramolecular nucleophilic aromatic substitution to the heteroarene is likely. Isoquinoline leads to zwitterionic 368 (94JOC3985). 

Cumulative Index of Heterocyclic Systems Pyrazolo[l,2- ]phthalazine (1583)... 

Tetrahydro- lH-pyrazolo[ 1,2-fc]phthalazine-1,5-dione (327) underwent oxidative ring fission to give 2-[a-(carboxymethyl)benzyl]-l(2f0-phthalazi-none (328) (iV-bromosuccinimide, CCI4, °C, h 42% a mechanism was... 

Optimal reaction conditions for the four-component domino reaction, developed by Reddy and coworkers, for the preparation of l-(lH-indol-2-yl)-lH-pyrazolo[l,2-l)]phthalazine-5,10-diones 4 were determined to be treatment of dialkylphthalates, hydrazine hydrate, indole-3-carboxaldehydes, and malono-nitrile or ethyl cyanoacetate with indium chloride (30mol%) as the Lewis... 

Multicomponent approaches toward the formation of more complex phthalazine-containing compounds were reported in 2014. A four-component one-pot condensation reaction was employed by Dabiri and coworkers to generate (1,2,3-triazol-4-yl)methyl-3-amino-5,10-dihydro-5,10-dioxo-lH-pyrazolo[l,2-f)]phthalazine-2-carboxylates 26 (Scheme 18) (14SC2037). Catalyzed by Cu(OAc)2 (10mol%) and sodium ascorbate (20mol%), the reaction of benzaldehyde derivatives (1 equivalent), azides (1 equivalent), prop-2-ynyl-2-cyanoacetate (27) (1 equivalent), and phthalhydrazide (28) (1... 

A similar version of this domino process to give pyrazolo[l,2-fo]phthalazine-5,10-diones 72 using 68, 69, and 71 as starting materials was reported by Singh and Raghuvanshi [47] (Scheme 12.26). 

Scheme 12.26 Multicomponent synthesis of pyrazolo[l,2-fa]phthalazine-5,l0-diones.

PMA-SiOj-Catalyzed Synthesis of lndazolo[1,2-6] phthalazine-Triones (25) and Pyrazolo[1,2-6] phthalazin-Triones (27)... 

Kiasat, A.R. and Davarpanah, J. 2013. Fe304 silica sulfuric acid nanoparticles An efficient reusable nanomagnetic catalyst as potent sohd acid for one-pot solvent-free synthesis indazolo[2,l-h]phthalazine-triones and pyrazolo[l,2-h]phthalazine-diones. J. Mol. Catal. A Chetn. 373 46-54. 

Furthermore, a three-component ultrasound-assisted protocol for the synthesis of pyrazolo[l,2-fc]phthalazine derivatives (53) was developed by Nabid et al. (2010). The reaction between phthalhydrazide (49), malononitrile (50) or ethyl cyanoacetate (51), and aromatic aldehydes (52) in ethanol at 50°C in the presence of triethylamine gave l/f-pyrazolo[l,2-fc]phthalazine-5,10-diones (53) in excellent yields (85%-97%) in 60 min (Scheme 8.17). 

A series of 3 -aminospiro[indoline-3,r-pyrazolo[l,2- ]phthalazine]-2,5, 10 -trione derivatives (181) have been synthesized by a one-pot three-component reaction of isatin (180), malononitrile (50) or ethyl cyanoacetate (51), and phthalhydrazide (49) catalyzed by piperidine under ultrasound irradiation (Scheme 8.59). For comparison, the reactions were carried out under both conventional and ultrasonic conditions. As a whole, improvement in rates and yields were observed when the reactions were carried out under sonication compared with classical conditions (Wang et al. 2012). 

Nabid, M. R., Rezaei, S. J. T., Ghahremanzadeh, R. and Bazgir, A. 2010. Ultrasound-assisted one-pot, three-component synthesis of lH-pyrazolo[l,2-h]phthalazine-5,10-diones. Ultrason. Sonochem. 17 159-161. 

Singh and coworkers reported a method for the synthesis of 2/f-indazolo[2,1 -fc]phthalazine-1,6,11 -triones and l//-pyrazolo[l,2-fc]phthalazine-5,10-diones under solvent-free... 

G. Shukla, R. K. Verma, G. K. Verma, M. S. Singh, Tetrahedron Lett. 2011,52,7195-7198. Solvent-free sonochemical one-pot three-component synthesis of 2fl-indazolo[2,l-i>]phthalazine-l, 6,11-triones and 17f-pyrazolo[l,2-i>]phthalazine-5,10-diones. 

R. Ghahremanzadeh, G. Shakibaei, A. Bazgir, Synlett 2008, 1129-1132. An efficient one-pot synthesis of IH-pyrazolo[ 1,2-h]phthalazine-5,10-dione derivatives. 

Cul NPs as efficient catalysts have been used for the preparation of H-pyrazolo[l,2-i]phthalazine-5,10-diones by the four-component condensation reaction of phthalic anhydride, hydrazine monohydrate, aromatic aldehydes, and malo-nonitrile or ethyl cyanoacetate under solvent-free conditions in good-to-excellent yields [39] (Scheme 5.9). The advantages offered by this method include short reaction times, excellent yields, simple procedure, easy workup, and the employment of a cost-effective catalyst. 

Safaei-Ghomi J, Shahbazi-Alavi H, Ziarati A, Teymuri R, Mohammad RS (2013) A highly flexible green synthesis of 1 /7-pyrazolo[l,2-h]phthalazine-5,10-dione derivatives with Cul nanoparticles as catalyst under solvent-free conditions. Chinese Chem Lett, http //dx.doi. org/10.1016/... 

Reza Nabid et al. [61] used ultrasonic irradiation for the synthesis of lH-pyrazolo[l,2-i7]phthalazine-5,10-diones (46) from the reaction of phthalhydrazide (43), malononitrile or cyanoacetate (44), and aromatic aldehydes (45) using triethylamine as catalyst xmder ethanolic medium. The principal advantage of the protocol is the use of an inexpensive and readily available catalyst, improving yields to 87-98%. Moreover, ethanol as solvent is considered to be relatively environmentally safe (Scheme 13). 

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