4-Substitutedphthalazines and phthalazinones: synthesis, characterization and β-adrenergic blocking activity

Synthetic and medicinal chemistry of phthalazines: Recent developments, opportunities and challenges

Fused diaza-heterocycles constitute the core structure of numerous bioactive natural products and effective therapeutic drugs. Among them, phthalazines have been recognized as remarkable structural leads in medicinal chemistry due to their wide application in pharmaceutical and agrochemical industries. Accessing such challenging pharmaceutical agents/drug candidates with high chemical complexity through synthetically efficient approaches remains an attractive goal in the contemporary medicinal chemistry and drug discovery arena. In this review, we focus on the recent developments in the synthetic routes towards the generation of phthalazine-based active pharmaceutical ingredients and their biological potential against various targets. The general reaction scope of these innovative and easily accessible strategies was emphasized focusing on the functional group tolerance, substrate and coupling partner compatibility/limitation, the choice of catalyst, and product diversification. These processes were also accompanied by the mechanistic insights where deemed appropriate to demonstrate meaningful information. Moreover, the rapid examination of the structure-activity relationship analyses around the phthalazine core enabled by the pharmacophore replacement/integration revealed the generation of robust, efficient, and more selective compounds with pronounced biological effects. A large variety of in silico methods and ADME profiling tools were also employed to provide a global appraisal of the pharmacokinetics profile of diaza-heterocycles. Thus, the discovery of new structural leads offers the promise of improving treatments for various tropical diseases such as tuberculosis, leishmaniasis, malaria, Chagas disease, among many others including various cancers, atherosclerosis, HIV, inflammatory, and cardiovascular diseases. We hope this review would serve as an informative collection of structurally diverse molecules enabling the generation of mature, high-quality, and innovative routes to support the drug discovery endeavors.

Facile Synthesis, Characterization, and Antimicrobial Evaluation of Novel Heterocycles, Schiff Bases, and N-Nucleosides Bearing Phthalazine Moiety

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, (1)H-NMR, (13)C-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.

Piperazine scaffold: A remarkable tool in generation of diverse pharmacological agents

Piperazine is one of the most sought heterocyclics for the development of new drug candidates. This ring can be traced in a number of well established, commercially available drugs. Wide array of pharmacological activities exhibited by piperazine derivatives have made them indispensable anchors for the development of novel therapeutic agents. The review herein highlights the therapeutic significance of piperazine derivatives. Various therapeutically active piperazine derivatives developed by several chemists are reported here.