Synthesis of 3-(benzylideneamino)-2-phenyl-5H-imidazo[1,2-b]pyrazole-7-carbonitriles via a four-component condensation reaction

Starch mediates and cements densely magnetite-coating of talc, giving an efficient nano-catalyst for three-component synthesis of imidazo[1,2-c]quinazolines

Hot-water-soluble starch (HWSS) was used as a powerful cementing material to produce nano-size conglomerates of talc and magnetite nanoparticles. Coordination of HWSS hydroxyl groups to iron atoms at surface of magnetite leads to grafting and encapsulation of its nanoparticles. The resulting nano-complex showed a higher loading capacity on talc than pristine magnetite nanoparticles. Only a minute amount of HWSS was detected in the fabricated nano-composite Talc\HWSS@Fe3O4. XPS study suggests a considerable interaction between HWSS and Fe3O4 nanoparticles, upon which some of the Fe+3 atoms on surface of Fe3O4 are reduced into Fe+2 atoms. ATR FT-IR spectra of the nano-composite revealed significant delamination of talc sheets on interaction with HWSS-coated Fe3O4 nanoparticles. The nano-composite displayed an efficient catalytic activity in the synthesis of new imidazo[1,2-c]quinazoline derivatives via Grobke-Blackburn-Bienaymé three-component reaction of 4-aminoquinazoline, arylaldehydes and isocyanide. The efficiency of the method was exemplified by synthesizing 7 new products in fairly high yields (68-83%) within short reaction times (24-30 min) using a catalytic amount of the catalyst under solvent-free condition at 120 °C. Clean and fast synthesis of the products and convenient separation of the robust nano-catalyst are the prominent advantages of the present method. The nano-catalyst was properly characterized.

Synthesis of pyrazolo[5′,1′:2,3]imidazo[1,5-c]quinazolin-6(5H)-ones and molecular docking study of their affinity against the COVID-19 main protease

A novel series of fused pyrazolo[5′,1′:2,3]imidazo[1,5-c]quinazolin-6(5H)-ones were synthesized and their affinity against the COVID-19 main protease was investigated using molecular docking study and compared to that of some used clinical drugs.

Synthesis and Crystal Structures of 4,5-Dihydroimidazo[1,5-b]pyrazol-6-ones

The synthesis of previously unattainable 2,5-disubstituted 4,5-dihydroimidazo[1,5-b]pyrazol-6-ones has been developed. Electrochemical reductions of readily available 2,2,2-trichloroethylideneacetophenones were followed by reaction with hydrazine, leading to 3-aryl-5-dichloromethyl-2-pyrazolines. These were treated with isocyanates to obtain the corresponding aminocarbonyl derivatives, which were found to be able to form an otherwise almost inaccessible imidazo[1,5-b]pyrazole ring system via a one-step reaction involving internal condensation followed by hydrogen chloride elimination and aromatization. The molecular­ structures of 2-(4-methylphenyl)-5-tosyl-4,5-dihydro­imidazo[1,5-b]pyrazol-6-one, 5-dichloromethyl-N-(4-chlorophenyl)-4,5-dihydro-3-p-tolylpyrazole-1-carboxamide, and 5-(4-bromophenyl)-2-p-tolyl-4,5-dihydroimidazo[1,5-b]pyrazol-6-one were determined by X-ray crystallographic analysis.

Solvent-free synthesis of isoindolo[2,1-c]pyrazolo[1,5-a]quinazoline and pyrazolo[5',1':2,3]pyrimido[6,1-a]isoindol derivatives through a one-pot three-component reaction

Some 5-substituted 3-aminopyrazoles were used for the synthesis of isoindolo[2,1-c]pyrazolo[1,5-a]quinazoline and pyrazolo[5',1':2,3]pyrimido[6,1-a]isoindol derivatives via a mild and efficient one-pot three-component reaction with 2-formylbenzoic acid and different CH-acids under solvent-free condition.

The status of isocyanide-based multi-component reactions in Iran (2010-2018)

Isocyanides as key intermediates and magic reactants have been widely applied in organic reactions for direct access to a broad spectrum of remarkable organic compounds. Although the history of these magical compounds dates back more than 100 years, it still has been drawing widespread attention of chemists who confirmed their versatility and effectiveness. Because of their wide spectrum of pharmacological, industrial and synthetic applications, many reactions with the utilization of isocyanides are reported in the literature. In this context, Iranian scientist played a significant role in the growth of isocyanides chemistry. The present review article covers literature from the period starting from 2010 onward and encompasses new synthetic routes and organic transformation involving isocyanides by Iranian researchers. During this period, a diverse range of isocyanide-based multi-component reactions (I-MCRs) has been reported such as a new modification of Ugi, post-Ugi, Passerini and Groebke-Blackburn-Bienayme condensation reactions, isocyanide-based [1 + 4] cycloaddition reactions, isocyanide-acetylene-based MCRs, isocyanide and Meldrum's acid-based MCRs, several unexpected reactions besides green mediums and novel catalytic systems for the synthesis of diverse kinds of pharmaceutically and industrially remarkable heterocyclic and linear organic compounds. This review also emphasizes the neoteric applications of I-MCR for the synthesis of valuable peptide and pseudopeptide scaffolds, enzyme immobilization and functionalization of materials with tailorable properties that can play important roles in the plethora of applications.

A four-component reaction: regio- and chemoselective formation of 7-amino-2-(tert-butyl)-5-aryl-4,5-dihydropyrazolo[1,5-a]pyrimidine-6-carbonitrile

A novel one-pot four-component reaction of an aldehyde, malononitrile, hydrazine and 4,4-dimethyl-3-oxopentanenitrile is described. As regio- and chemoselective products, 7-amino-2-(tert-butyl)-5-aryl-4,5-dihydropyrazolo[1,5-a]pyrimidine-6-carbonitriles are formed during the course of the reaction.

Oxidant-directed chemoselective sulfonylation and sulfonyloximation of alkenes via cleaving the C–S bond in TosMIC

Oxidant-directed chemoselective sulfonylation and sulfonyloximation reactions for the divergent synthesis of valuable vinyl sulfones and α-sulfonylethanone oximes are developed.

5-Amino-pyrazoles: potent reagents in organic and medicinal synthesis

5-Amino-pyrazoles have proven to be a class of fascinating and privileged organic tools for the construction of diverse heterocyclic or fused heterocyclic scaffolds. This review presents comprehensively the applications of 5-amino-pyrazoles as versatile synthetic building blocks in the synthesis of remarkable organic molecules with an emphasis on versatile functionalities. Following a brief introduction of synthesis methods, planning strategies to construct organic compounds, particularly diverse heterocyclic scaffolds, such as poly-substituted heterocyclic compounds and fused heterocyclic compounds via 5-amino-pyrazoles, have been summarized. Fused heterocycles are classified as bicyclic, tricyclic, tetracyclic, and spiro-fused pyrazole derivatives. These outstanding compounds synthesized via wide variety of approaches include conventional reactions, one-pot multi-component reactions, cyclocondensation, cascade/tandem protocols, and coupling reactions. 5-Amino-pyrazoles represent a class of promising functional reagents, similar to the biologically active compounds, highlighted with diverse applications especially in the field of pharmaceutics and medicinal chemistry. Notably, this critical review covers the articles published from 1981 to 2018.

Aminoazole-Based Diversity-Oriented Synthesis of Heterocycles

The comprehensive review contains the analysis of literature data concerning reactions of heterocyclization of aminoazoles and demonstrates the application of these types of transformations in diversity-oriented synthesis. The review is oriented to wide range of chemists working in the field of organic synthesis and both experimental and theoretical studies of nitrogen-containing heterocycles.

Imidazo[1,2-b]pyrazole-7-carboxamides Induce Apoptosis in Human Leukemia Cells at Nanomolar Concentrations

Leukemia, the malignancy of the hematopoietic system accounts for 10% of cancer cases with poor overall survival rate in adults; therefore, there is a high unmet medical need for the development of novel therapeutics. Eight imidazo[1,2-b]pyrazole-7-carboxamides have been tested for cytotoxic activity against five leukemia cell lines: Acute promyelocytic leukemia (HL-60), acute monocytic leukemia (THP-1), acute T-lymphoblastic leukemia (MOLT-4), biphenotypic B myelomonocytic leukemia (MV-4-11), and erythroleukemia (K-562) cells in vitro. Imidazo[1,2-b]pyrazole-7-carboxamides hampered the viability of all five leukemia cell lines with different potential. Optimization through structure activity relationship resulted in the following IC50 values for the most effective lead compound DU385: 16.54 nM, 27.24 nM, and 32.25 nM on HL-60, MOLT-4, MV-4-11 cells, respectively. Human primary fibroblasts were much less sensitive in the applied concentration range. Both monolayer or spheroid cultures of murine 4T1 and human MCF7 breast cancer cells were less sensitive to treatment with 1.5⁻10.8 μM IC50 values. Flow cytometry confirmed the absence of necrosis and revealed 60% late apoptotic population for MV-4-11, and 50% early apoptotic population for HL-60. MOLT-4 cells showed only about 30% of total apoptotic population. Toxicogenomic study of DU385 on the most sensitive MV-4-11 cells revealed altered expression of sixteen genes as early (6 h), midterm (12 h), and late response (24 h) genes upon treatment. Changes in ALOX5AP, TXN, and SOD1 expression suggested that DU385 causes oxidative stress, which was confirmed by depletion of cellular glutathione and mitochondrial membrane depolarization induction. Imidazo[1,2-b]pyrazole-7-carboxamides reported herein induced apoptosis in human leukemia cells at nanomolar concentrations.

Synthesis of novel series of 7,7′-(substituted methylene)bis-imidazo[1,2-b]pyrazoles via an acid catalyzed one-pot three-component reaction

An efficient and rapid synthesis of new series of N-alkyl-2-aryl-5H-imidazo[1,2-b]pyrazoles has been achieved in high yields through a three-component reaction of 3-amino-4-substituted pyrazoles, aromatic aldehydes and isocyanides mediated by acid catalysts.

New tricks of well-known aminoazoles in isocyanide-based multicomponent reactions and antibacterial activity of the compounds synthesized

The well-known aminoazoles, 3-amino-5-methylisoxazole and 5-amino-N-aryl-1H-pyrazole-4-carboxamides, were studied as an amine component in Ugi and Groebke-Blackburn-Bienaymé multicomponent reactions. The first example of an application of aminoazoles in an Ugi four-component reaction was discovered and novel features of a Groebke-Blackburn-Bienaymé cyclocondensation are established and discussed. The heterocycles obtained were evaluated for their antibacterial activity and several of them demonstrated a weak antimicrobial effect, but for most of the compounds a 30-50% increase in biomass of Gram-positive strains (mainly B. subtilis) compared to control was observed.

Silver-catalyzed cascade reaction of tosylmethyl isocyanide (TosMIC) with propargylic alcohols to (E)-vinyl sulfones: dual roles of TosMIC

An silver-catalyzed cascade reaction of tosylmethyl isocyanide (TosMIC) with propargylic alcohols for the synthesis of (E)-vinyl sulfones has been developed where TosMIC plays a dual role as both the reactant in the allenylation of propargylic alcohols and the sulfonyl source.

Facile synthesis of 1H-imidazo[1,2-b]pyrazoles via a sequential one-pot synthetic approach

5-Aminopyrazole-4-carbonitrile and ethyl 5-aminopyrazole-4-carboxylate, as potential trifunctional building blocks are introduced in a facile, chemo- and regioselective multicomponent assembly of imidazo[1,2-b]pyrazoles via the Groebke–Blackburn–Bienaymé reaction (GBB reaction). Besides the synthetic elaboration of a green-compatible isocyanide-based access in three-component mode, we describe an operationally simple, one-pot two-step GBB protocol for the rapid construction of a 46 membered imidazo[1,2-b]pyrazole library with yields up to 83%.

New imidazo[1,2-b]pyrazoles as anticancer agents: synthesis, biological evaluation and structure activity relationship analysis

Synthesis and functionalization strategies of the imidazo[1,2-b]pyrazole core were developed giving a rapid access to three series of novel imidazo[1,2-b]pyrazole type derivatives: C-2/C-6/C-7 trisubstituted, C-2/C-3/C-6 tri(hetero)arylated and C-2/C-3/C-6/C-7 tetrasubstituted imidazo[1,2-b]pyrazoles. 39 of the synthetized products were evaluated for in vitro anticancer activity using the MTT colorimetric assay against 5 human and 1 murine cancer cell lines. Promising in vitro growth inhibitory activities were exhibited by some of the target compounds. Of the 39 evaluated products, 4 displayed an IC50 ≤ 10 μM in the 6 cell lines analyzed (compounds 4d, 4g, 9a, 11a). A structure activity relationship analysis is also reported in this paper.

Fused Imidazopyrazoles: Synthetic Strategies and Medicinal Applications

The current review summarizes the known synthetic routes of fused imidazopyrazoles. This review is classified into two main categories based on the type of annulations, for example, annulation of the imidazole ring onto a pyrazole scaffold or annulation of the pyrazole ring onto an imidazole scaffold. Some medicinal applications of imidazopyrazoles are mentioned.