Silica Sulfuric Acid: An Efficient, Reusable, Heterogeneous Catalyst for the One-Pot, Five-Component Synthesis of Highly Functionalized Piperidine Derivatives

Recent Developments on Five-Component Reactions

Multicomponent reactions (MCRs) have inherent advantages in pot, atom, and step economy (PASE). This important green synthetic approach has gained increasing attention due to high efficiency, minimal waste, saving resources, and straightforward procedures. Presented in this review article are the recent development on 5-compoment reactions (5CRs) of the following six types: (I) five different molecules A + B + C + D + E; pseudo-5CRs including (II) 2A + B + C + D, (III) 2A + 2B + C, (IV) 3A + B + C, (V) 3A + 2B, and (VI) 4A + B. 5CRs with more than five-reaction centers are also included.

Silica–sulfuric acid and alumina–sulfuric acid: versatile supported Brønsted acid catalysts

–SO3H functionalized silica and alumina have emerged as efficient and eco-compatible heterogeneous solid acid catalysts for the construction of various important molecular skeletons.

Access to molecular complexity. Multicomponent reactions involving five or more components

The evaluation of the significance of a chemical transformation addresses many factors, including such important characteristics as the number of chemical bonds formed in one step, the reaction time, labour intensity, the cost of reactants and catalysts and so on. The amount of waste produced in the reaction has also gained increasing importance in recent years. Multicomponent reactions (MCRs) occupy a special place as a synthetic tool in modern organic chemistry. These reactions allow the synthesis of target products with complex structures, minimizing labour costs. This review summarizes the literature on multicomponent reactions involving five or more components. The data in the review are classified according to the number of reactants participating in the reaction and the types of reactions. It is worth noting that in some cases, these transformations can be a part of a domino process, making this classification difficult, if not impossible. The structural diversity of the reaction products greatly increases with increasing number of components involved in the MCR, which becomes virtually unlimited when using combinations of MCRs. This review highlights the main trends of past decades in the field of MCRs. The last two decades have witnessed an explosive growth in the number of publications in this area of chemistry.

The bibliography includes 309 references.

Facile Assembling of Novel 2,3,6,7,9-pentaazabicyclo- [3.3.1]nona-3,7-diene Derivatives under Microwave and Ultrasound Platforms

Reactions of a series of 3-oxo-2-arylhydrazonopropanal derivatives with two molar ratio of ammonium acetate afforded a library of tetrasubstituted 2,3,6,7,9-pentaazabicyclo[3.3.1]nona- 3,7-diene derivatives in good to excellent isolated yields. The reaction was activated with triethylamine catalyst under three different heating modes: thermal, ultrasonic and microwave irradiating conditions in ethanol solvent. The structures of the isolated products were fully characterized by spectral and analytical data as well as X-ray single crystal of selected examples.

Designing a novel tetradentate polyoxometalate eco-catalyst for the synthesis of β-aminocyclohexanone derivatives in water

The synthesis of a series of known β-aminocyclohexanones has been accomplished using pentaerythrityl tetramethyl imidazolium phosphotungstate (C(MIM-PTA)₄) as a new tetradentate acidic catalyst. It was prepared via condensation of pentaerythrityl tetrabromide with methyl imidazole. Then, bulky anion H₂PW₁₂O₄₀¹⁻ was substituted with Br⁻ in the structure. This tetradentate catalyst provides designable cations and anions. Anions have two types of acids, acidic protons, and metals with Lewis acidity. In order to test the efficient catalytic behavior of the tetradentate catalyst, a controlled reaction was performed using benzaldehyde, aniline and cyclohexanone. Imine from the condensation of benzaldehyde and aniline was observed in the absence of ionic catalyst instead of desired products. Thus, this reaction would be attractive because of the time, energy, and raw material saving considerations because of the absence of isolation of intermediates and stereospecificity. The catalyst shows high catalytic activity such that after four recycles the product was obtained with high yield and purity. This reaction was performed at room temperature. Although high temperature could improve the reaction rate, it contributes to side reactions and oxidation of aldehyde and amine. The catalyst was characterized by elemental analysis, FT-IR spectroscopy, ¹H NMR, ¹³C NMR, and TGA.

The synthesis of a series of known β-aminocyclohexanones has been accomplished using pentaerythrityl tetramethyl imidazolium phosphotungstate (C(MIM-PTA)₄) as a new tetradentate acidic catalyst.

A Novel and Efficient Five-Component Synthesis of Pyrazole Based Pyrido[2,3-d]pyrimidine-diones in Water: A Triply Green Synthesis

A novel one pot synthesis of pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidine-diones, via a five-component reaction, involving, hydrazine hydrate, ethyl acetoacetate, and 1,3-dimethyl barbituric acid, an appropriate aryl aldehydes and ammonium acetate catalyzed via both of heterogeneous and homogeneous catalysis in water, is reported.

Synthesis of functionalized dihydro-2-oxypyrroles and tetrahydropyridines using 2,6-pyridinedicarboxylic acid as an efficient and mild organocatalyst

Simple and mild one-pot protocols for the synthesis of diversely functionalized dihydro-2-oxypyrroles and tetrahydropyridines using catalytic amounts of 2,6-PDCA.

Recent developments in multicomponent synthesis of structurally diversified tetrahydropyridines

Tetrahydropyridines (THPDs) have recognized as a major constituent of naturally occurring alkaloids and exhibits various biological and pharmacological profiles. For their synthesis, MCRs are employed as an excellent tool to generate vast libraries.