Microwave Irradiation and Multicomponent Reactions. In: Orru RVA, Ruijter E, editors. Synthesis of Heterocycles via Multicomponent Reactions II. Berlin: Springer Berlin Heidelberg; 2010. pp. 169-230. [DOI: 10.1007/7081_2010_45]

A novel superparamagnetic powerful guanidine-functionalized γ-Fe2O3 based sulfonic acid recyclable and efficient heterogeneous catalyst for microwave-assisted rapid synthesis of quinazolin-4(3H)-one derivatives in Green media

The novel organic–inorganic nanohybrid superparamagnetic (γ-Fe₂O₃@CPTMS–guanidine@SO₃H) nanocatalyst modified with sulfonic acid represents an efficient and green catalyst for the one-pot synthesis of quinazolin-4(3H)-one derivatives via three-component condensation reaction between anthranilic acid, acetic anhydride and different amines under microwave irradiation and solvent-free conditions (4a–q). XRD, FT-IR, FE-SEM, TGA, VSM and EDX were used to characterize this new magnetic organocatalyst. Outstanding performance, short response time (15–30 min), simple operation, easy work-up procedure, and avoidance of toxic catalysts can be regarded as its significant advantages. Moreover, it can be easily separated from the reaction solution through magnetic decantation using an external magnet, and recycled at least six times without notable reduction in its activity.

A novel organic–inorganic nanohybrid superparamagnetic nanocatalyst (γ-Fe₂O₃@CPTMS–guanidine@SO₃H) represents an efficient and green catalyst for the one-pot synthesis of quinazolin-4(3H)-one derivatives via a three-component condensation reaction.

Synthesis and biological evaluation of novel benzo[a]pyridazino[3,4-c]phenazine derivatives

A convenient microwave-assisted one-pot four-component synthetic approach was developed en route to novel functionalized benzo[a]pyridazino[3,4-c]phenazine derivatives starting from 2-hydroxy-1,4-naphthoquinone, aromatic aldehydes, methyl hydrazine and o-phenylenediamine. Nine new derivatives were successfully synthesized and subsequently evaluated in terms of their biological profiles. The results revealed good cytotoxic activities of compounds 6a, 6h against KB, HepG2, Lu1 and MCF7 human cancer cell lines. Besides that, compound 6d exhibited promising antimicrobial activities toward Staphylococcuc aureus and Bacillus subtilis bacterial strains with IC₅₀ < 6 μM.

Post-Ugi Cyclization for the Construction of Diverse Heterocyclic Compounds: Recent Updates

Multicomponent reactions (MCRs) have proved as a valuable tool for organic and medicinal chemist because of their ability to introduce a large degree of chemical diversity in the product in a single step and with high atom economy. One of the dominant MCRs is the Ugi reaction, which involves the condensation of an aldehyde (or ketone), an amine, an isonitrile, and a carboxylic acid to afford an α-acylamino carboxamide adduct. The desired Ugi-adducts may be constructed by careful selection of the building blocks, opening the door for desired post-Ugi modifications. In recent times, the post-Ugi transformation has proved an important synthetic protocol to provide a variety of heterocyclic compounds with diverse biological properties. In this review, we have discussed the significant advancements reported in the recent literature with the emphasis to highlight the concepts and synthetic applications of the derived products along with critical mechanistic aspects.

Synergy Effects in the Chemical Synthesis and Extensions of Multicomponent Reactions (MCRs)-The Low Energy Way to Ultra-Short Syntheses of Tailor-Made Molecules

Several novel methods, catalysts and reagents have been developed to improve organic synthesis. Synergistic effects between reactions, reagents and catalysts can lead to minor heats of reaction and occur as an inherent result of multicomponent reactions (MCRs) and their extensions. They enable syntheses to be performed at a low energy level and the number of synthesis steps to be drastically reduced in comparison with ‘classical’ two-component reactions, fulfilling the rules of Green Chemistry. The very high potential for variability, diversity and complexity of MCRs additionally generates an extremely diverse range of products, thus bringing us closer to the aim of being able to produce tailor-made and extremely low-cost materials, drugs and compound libraries.

Microwave-Assisted and L-proline Catalysed Domino Cyclisation in an Aqueous Medium: A Rapid, Highly Efficient and Green Synthesis of Benzo[a]Phenazine Annulated Heterocycles

A highly efficient one-pot, two-step microwave-assisted procedure was applied for the rapid and green synthesis of benzo[a]phenazine annulated heterocyclic ring systems from the three- or four-component condensation reactions of 2-hydroxynaphthalene-1,4-dione, o-phenylenediamine, aromatic aldehydes and 1,3-indandione using L-proline as a bifunctional organocatalyst in water. This new procedure has a number of advantages such as high yields, very short reaction times, operational simplicity, simple work-up procedures and avoidance of hazardous or toxic catalysts and organic solvents. Moreover, the catalyst can be recovered and reused several times without much loss of its performance.

Three-component reaction of a 2-aminoazine, a 2-oxoaldehyde, and a cyclic 1,3-dicarbonyl compound for the synthesis of imidazo[1,2-a]azine derivatives

A three-component reaction of a 2-aminoazine, a 2-oxoaldehyde, and a cyclic 1,3-dicarbonyl compound providing access toward a novel class of imidazo[1,2-a]azine derivatives was developed and studied. The scope of the process was thoroughly explored under three different reaction conditions resulting in the generation of a small library of title compounds and highlighting the possibility of case-specific approach.

Multicomponent reactions in nucleoside chemistry

This review covers sixty original publications dealing with the application of multicomponent reactions (MCRs) in the synthesis of novel nucleoside analogs. The reported approaches were employed for modifications of the parent nucleoside core or for de novo construction of a nucleoside scaffold from non-nucleoside substrates. The cited references are grouped according to the usually recognized types of the MCRs. Biochemical properties of the novel nucleoside analogs are also presented (if provided by the authors).

High regioselective ultrasonic-assisted synthesis of 2,7-diaryl-4,7-dihydropyrazolo[1,5-a]pyrimidine-5-carboxylic acids

New and high regioselective method of the synthesis of 2,7-diaryl-4,7-dihydropyrazolo[1,5-a]pyrimidine-5-carboxylic acids by reaction of 3-aryl-5-aminopyrazoles with arylidenpyruvic acid at room temperature under ultrasonication was developed and discussed.