2-(4,5-Dihydro-1H-imidazol-2-yl)indazole (indazim) derivatives as selective I2 imidazoline receptor ligands

A review of poly(ADP-ribose)polymerase-1 (PARP1) role and its inhibitors bearing pyrazole or indazole core for cancer therapy

Cancer is a disease with a high mortality rate characterized by uncontrolled proliferation of abnormal cells. The hallmarks of cancer evidence the acquired cells characteristics that promote the growth of malignant tumours, including genomic instability and mutations, the ability to evade cellular death and the capacity of sustaining proliferative signalization. Poly(ADP-ribose) polymerase-1 (PARP1) is a protein that plays key roles in cellular regulation, namely in DNA damage repair and cell survival. The inhibition of PARP1 promotes cellular death in cells with homologous recombination deficiency, and therefore, the interest in PARP protein has been rising as a target for anticancer therapies. There are already some PARP1 inhibitors approved by Food and Drug Administration (FDA), such as Olaparib and Niraparib. The last compound presents in its structure an indazole core. In fact, pyrazoles and indazoles have been raising interest due to their various medicinal properties, namely, anticancer activity. Derivatives of these compounds have been studied as inhibitors of PARP1 and presented promising results. Therefore, this review aims to address the importance of PARP1 in cell regulation and its role in cancer. Moreover, it intends to report a comprehensive literature review of PARP1 inhibitors, containing the pyrazole and indazole scaffolds, published in the last fifteen years, focusing on structure-activity relationship aspects, thus providing important insights for the design of novel and more effective PARP1 inhibitors.

A review on synthetic strategy, molecular pharmacology of indazole derivatives, and their future perspective

With different nitrogen-containing heterocyclic moieties, Indazoles earn one of the places among the top investigated molecules in medicinal research. Indazole, an important fused aromatic heterocyclic system containing benzene and pyrazole ring with a chemical formula of C₇ H₆ N₂ , is also called benzopyrazole. Indazoles consist of three tautomeric forms in which 1H-tautomers (indazoles) and 2H-tautomers (isoindazoles) exist in all phases. The tautomerism in indazoles greatly influences synthesis, reactivity, physical and even the biological properties of indazoles. The thermodynamic internal energy calculation of these tautomers points view 1H-indazole as the predominant and stable form over 2H-indazole. The natural source of indazole is limited and exists in alkaloidal nature (i.e., nigellidine, nigeglanine, nigellicine, etc.) found from Nigella plants. Some of the FDA-approved drugs like Axitinib, Entrectinib, Niraparib, Benzydamine, and Granisetron are being used to treat renal cell cancer, non-small cell lung cancer (NSCLC), epithelial ovarian cancer, chronic inflammation, chemotherapy-induced nausea, vomiting, and many more uses. Besides all these advantages regarding its biological activity, the main issue about indazoles is the less abundance in plant sources, and their synthetic derivatives also often face problems with low yield. In this review article, we discuss its chemistry, tautomerism along with their effects, different schematics for the synthesis of indazole derivatives, and their different biological activities.

Ultrasound promoted mild and facile one-pot, three component synthesis of 2H-indazoles by consecutive condensation, CN and NN bond formations catalysed by copper-doped silica cuprous sulphate (CDSCS) as an efficient heterogeneous nano-catalyst

An ultrasonic promoted facile and convenient one-pot three-component procedure for the synthesis of 2H-indazole derivatives using copper-doped silica cuprous sulphate (CDSCS) as a heterogeneous nano-catalyst has been described. In this approach, ultrasonic mediated reaction of different substituted 2-bromobenzaldehydes, structurally diverse primary amines, and tetrabutylammonium azide (TBAA) as an azide source in the presence of CDSCS in DMSO at room temperature furnishes 2H-indazoles in good to excellent yields. Utilizing ultrasonic irradiation techniques provided the dramatic improvements in terms of higher yields and shorter reaction times compared with conventional heating method.

Davis-Beirut reaction: route to thiazolo-, thiazino-, and thiazepino-2H-indazoles

Methods for the construction of thiazolo-, thiazino-, and thiazepino-2H-indazoles from o-nitrobenzaldehydes or o-nitrobenzyl bromides and S-trityl-protected 1°-aminothioalkanes are reported. The process consists of formation of the requisite N-(2-nitrobenzyl)(tritylthio)alkylamine, subsequent deprotection of the trityl moiety with TFA, and immediate treatment with aq. KOH in methanol under Davis–Beirut reaction conditions to deliver the target thiazolo-, thiazino-, or thiazepino-2H-indazole in good overall yield. Subsequent S-oxidation gives the corresponding sulfone.

N-(Imidazolidin-2-ylidene)-1-arylmethanamine oxides: synthesis, structure and pharmacological evaluation

A high yielding three-step procedure was applied for the synthesis of N-(imidazolidin-2-ylidene)-1-arylmethanamine oxides 3 (α-aminonitrones) starting from the easily accessible imidazolidin-2-one O-benzyl oxime 1. The α-aminonitrone-α-iminohydroxyloamine tautomerism of these products was studied theoretically and the structures of the synthesised compounds were confirmed by single crystal X-ray crystallographic analysis. The compounds were evaluated in vitro for their binding affinities to α(1) and α(2) adrenoceptors as well as imidazoline I(1) and I(2) receptors. The highest potencies at the α(2) adrenergic receptors were observed for compounds bearing biphenyl (4h, K(i)  = 9 nM) and naphthyl (4i, K(i)  = 92 nM) moieties. Compounds 4h and 4i were further tested in vivo for their cardiovascular and sedative-hypnotic effects in rats.

Synthesis of 2H-indazoles by the [3 + 2] dipolar cycloaddition of sydnones with arynes

A rapid and efficient synthesis of 2H-indazoles has been developed using a [3 + 2] dipolar cycloaddition of sydnones and arynes. A series of 2H-indazoles have been prepared in good to excellent yields using this protocol, and subsequent Pd-catalyzed coupling reactions can be applied to the halogenated products to generate a structurally diverse library of indazoles.

Consecutive condensation, C-N and N-N bond formations: a copper- catalyzed one-pot three-component synthesis of 2H-indazole

2H-Indazoles are synthesized using copper-catalyzed, one-pot, three-component reactions of 2-bromobenzaldehydes, primary amines, and sodium azide. A copper catalyst plays the key role in the formation of C-N and N-N bonds. This method has a broad substrate scope with a high tolerance for a variety of functional groups.

Synthesis of 2H-indazoles by the [3 + 2] cycloaddition of arynes and sydnones

A rapid and efficient synthesis of 2H-indazoles has been developed, which involves the [3 + 2] dipolar cycloaddition of arynes and sydnones. The process proceeds under mild reaction conditions in good to excellent yields.

CuCl-Induced Formation and Migration of Isoindazolyl Carbenoids

Two azo-ene-butadiyne conjugated systems undergo CuCl-mediated cyclization to afford isoindazolyl carbenoids that could be trapped with 2,3-dimethyl-2-butene as [2+1] cycloaddition products. X-ray structure analysis of the resultant cyclopropanes showed that formal migration to the distal carbenoid isomer and subsequent trapping had occurred. The possible CuCl-induced cyclization/migration pathways were explored using density functional theory, which indicated that the reaction most likely occurred via coordination of CuCl to the distal alkyne bond.

2-(4,5-Dihydroimidazol-2-yl)benzimidazoles as highly selective imidazoline I2/adrenergic α2 receptor ligands

2-(4,5-Dihydroimidazol-2-yl)benzimidazoles have been identified as selective imidazoline I2/alpha2-adrenoceptor ligands. 4-Methyl (2) and 4-chloro (4) derivatives display I2 affinity at nanomolar concentration (Ki=4.4 and 17.7 nM, respectively) and high I2/alpha2 selectivity ratio=4226 and 5649, respectively. An evidence has been obtained that pKa value influences considerably the I2/alpha2-selectivity ratio of this class of imidazoline I2 receptor ligands.

The synthesis and antimicrobial activity of some new methyl N-arylthiocarbamates, dimethyl N-aryldithiocarbonimidates and 2-arylamino-2-imidazolines

Methyl N-arylthiocarbamates (2a-d) and dimethyl N-aryldithiocarbonimidates (2e-i) were synthesized from the reaction of aromatic amines with carbon disulfide and methyl iodide and NaOH in various quantitative amounts. 2-Arylamino-2-imidazolines (3a-i) were prepared by heating both methyl N-arylthiocarbamates (2a-d) and dimethyl N-aryldithiocarbonimidates (2e-i) with 1,2-diaminoethane under reflux. o-chlorobenzyl derivatives of [1,3,4]-thiadiazole-2-yl substituted aminoimidazoline compounds were synthesized by treatment of [1,3,4]-thiadiazole-2-yl substituted aminoimidazolines (3h-i) with 2-benzyl chloride in basic medium and DMSO. Some of the synthesized compounds were tested in vitro for their antimicrobial activity. All of the selected compounds showed some antimicrobial activity against test microorganisms. Compounds 2f and 3f which have 1,3-benzothiazol ring exhibited a weak activity against Candida globrata.

Synthesis of 2,3,5,6-tetrahydro-3H-imidazo[2,1-b] [1,3,5]benzotriazepines and their oxidative ring contraction into 1-(4,5-dihydro-1H-imidazol-2-yl)-1H-benzimidazoles

Syntheses of novel 5-aryl-2,3,5,6-tetrahydro-3H-imidazo[2,1-b] [1,3,5]benzotriazepine derivatives 3a-g were performed by reacting 2-(2-aminoarylimino)imidazolidines 1a-b with corresponding aryl aldehydes. The compounds 3 incorporating aminal group upon treatment with 2,3-dichloro-5,6-dicyano-1,2-benzoqinone (DDQ) underwent the oxidative ring contraction to give 1-(4,5-dihydro-1H-imidazol-2-yl)-2-aryl-benzimidazoles 4a-g. Reactions of the compounds 1a-c with carbonyldiimidazole (CDI) afforded novel 2,3,5,6-tetrahydro-1H-imidazo[2,1-b] [1,3,5]benzotriazepin-5-ones 5a-c which when heated in boiling methanol gave the corresponding 1-(4,5-dihydro-1H-imidazol-2-yl)-1,3-dihydro-2H-benzimidazol-2-ones 6a-c. Radioligand binding studies using rat central imidazoline I2 receptors and alpha2-adrenoceptors demonstrated that benzimidazoles 4a-g display a low affinity (microM) for these receptors while benzimidazol-2-ones 6a-b elicited a moderate affinity for I2 receptor with Ki values of 490 and 220 nM, respectively.

Imidazoline binding sites and their ligands: an overview of the different chemical structures

Since Bousquet et al. discovered the imidazoline binding sites (IBS) two decades ago, when they realized that the antihypertensive drug clonidine interacts not only with the alpha2-adrenenoceptors (alpha2-AR) but also with a distinct imidazoline preferring binding site, these receptors have been paid a great deal of attention. At least two subtypes, I1 and I2, have been characterised based on their binding affinity for different radioligands, but their structures still remain unknown. The pharmacological profile of these IBSs has been the objective of several and very thorough reviews. However, a medicinal chemistry overview of the different IBS ligands prepared to date has never been attempted. In this study, we attempt to compile all the different chemical structures reported to date as IBS ligands and classify them in function of their chemical structure and binding affinity for the different IBS subtypes. Thus, we comment on the different endogenous IBS ligands known as well as the drugs described to interact with the I1-IBS which have found application as antihypertensive drugs. Then, we review those compounds described in the literature to interact with the I2-IBS, classifying them by their chemical families (imidazolines, guanidines, 2-aminoimidazolines, beta-carbolines). Finally, some conclusions are drawn.