Design of multifaceted acidic 1,3-disulfoimidazolium chlorometallate ionic systems as heterogeneous catalysts for the preparation of β-amino carbonyl compounds

[Msim]CuCl3: as an efficient catalyst for the preparation of 5-amino-1H-pyrazole-4-carbonitriles by anomeric based oxidation

3-Methyl-1-sulfonic acid imidazolium trichlorido copper (II) {[Msim]CuCl3} was prepared and used as a new catalyst for the preparation of 5-amino-1H-pyrazole-4-carbonitriles. In this reaction, the pyrazole ring was formed by an anomeric and vinylogous anomeric effect in the structure of the product.

Organocatalyzed Heterocyclic Transformations In Green Media: A Review

Background:

Since the discovery of metal-free catalysts or organocatalysts about twenty years ago, a number of small molecules with different structures have been used to accelerate organic transformations. With the development of environmental awareness, to obtain highly efficient scaffolds, scientists have directed their studies towards synthetic methodologies that minimize or preferably eliminate the formation of waste, avoid toxic solvents and reagents and use renewable starting materials as far as possible.

Methods:

In this connection, the organocatalytic reactions providing efficiency and selectivity for most of the transformations have become an endless topic in organic chemistry since several advantages from both practical and environmental standpoints. Organocatalysts contributing to the transformation of reactants into products with the least possible waste production, have been serving the concept of green chemistry.

Results and Conclusion:

Organocatalysts have been classified based on their binding capacity to the substrate with covalent or noncovalent interactions involving hydrogen bonding and electrostatic interaction. Diverse types of small organic compounds including proline and its derivatives, phase-transfer catalysts, (thio)urease, phosphoric acids, sulfones, N-oxides, guanidines, cinchona derivatives, aminoindanol, and amino acids have been utilized as hydrogen bonding organocatalysts in different chemical transformations.

Recent advances and prospects in the Zn-catalysed Mannich reaction

Zn-catalysed reactions are ubiquitously important due to their inexpensive, generally less toxic and atom-economic nature. According to the modern criteria of sustainability, their use in a catalytic manner is a highly desirable goal, especially when using chiral ligands. Considering the relevance of well-established zinc-mediated C-C bond formation reactions, it is relatively surprising that the use of Zn as a catalyst is still underdeveloped, especially in comparison with other transition metals. The vast majority of natural molecules, including proteins, nucleic acids and most biologically active compounds, contain nitrogen. Consequently, developing new synthetic methods for the construction of nitrogenous molecules receives great attention from organic chemists. The Mannich reaction is a very basic and very useful platform for the development of several such nitrogen-containing molecules. In this review, we summarise the recent advancements in the Zn-catalysed Mannich reaction, covering the literature from 2011 to 2020.

Development of N,N-disulfo-1,1,3,3-tetramethylguanidinium chlorometallates as heterogeneous catalysts for one pot synthesis of 1,2-dihydro-1-aryl-3H-naphth[1, 2-e][1,3]oxazin-3-one derivatives

Background:

Four members of N,N-disulfo-1,1,3,3-tetramethylguanidinium chlorometallates [DSTMG]n[X], where n= 1 or 2; X= FeCl4 - , Zn2Cl6 2-, NiCl4 2-, MnCl4 2- were synthesized as solid Brønsted-Lewis acidic compounds and studied the catalytic activity with the most acidic salt for three-component synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2- e][1,3]oxazin-3-ones.

Methods:

N,N-disulfo-1,1,3,3-tetramethylguanidinium chlorometallates of the four transition metal cations such as Fe(III), Zn(II), Ni(II) and Mn(II) were prepared after treatment of the parent ionic liquid N,N-disulfo-1,1,3,3- tetramethylguanidinium chloride [DSTMG][Cl] with the respective metal chlorides in different mole fractions at 75 ºC. The synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2-e][1,3]oxazin-3-ones was carried out via three-component reaction of 2-naphthol, aromatic aldehydes and urea under neat condition at 90 ºC using 7 mol% of the [DSTMG][FeCl4] catalyst.

Results:

The characterization of synthesized chlorometallates were done using spectroscopic and other analytical techniques including thermogravimetric analysis and Hammett acidity studies. Among the four salts, the salt of Fe(III) ion was observed as the strong Brønsted acidic hydrophobic salt and thus chosen for the catalytic study.

Conclusion:

A new type of chlorometallates of guanidinium cation with composition [DSTMG]n[X], where X= FeCl4 - /Zn2Cl6 2-/ NiCl4 2-/ MnCl4 2- and n= 1 or 2 were developed as –SO3H functionalized solid acids with varied thermal stability (150-250 ºC) and physisorbed water (0-20%) as observed from the thermogravimetric study. From them, the most Brønsted acidic Fe(III) salt was employed as efficient recyclable heterogeneous catalyst for the one-pot synthesis of 1,2- dihydro-1-aryl-3H-naphth[1,2-e][1,3]oxazin-3-ones in neat condition.

Novel functionalized magnetic ionic liquid green separation technology coupled with high performance liquid chromatography: A rapid approach for determination of estrogens in milk and cosmetics

Several magnetic ionic liquids (MILs), [P_6,6,6,14⁺][FeCl₄^-], [P_6,6,6,14⁺]₂[MnCl₄^2-], [P_6,6,6,14⁺]₂[CoCl₄^2-] and [P_6,6,6,14⁺]₂[NiCl₄^2-] were synthesized and applied for the extraction of six estrogens (estrone, estradiol, 17-α-hydroxyprogesterone, chloromadinone 17-acetate, megestrol 17-acetate and medroxyprogesterone 17-acetate) in dispersive liquid-liquid microextraction (DLLME). The [CoCl₄^2-]-based MIL was selected as extraction solvent for the separation and concentration of estrogens from milk and cosmetics due to its visual recognition, no sign of hydrolysis, solution acquisition easier and the highest extraction capacity. In addition, the [CoCl₄^2-]-based MIL with low UV absorbance allows direct analysis of the extraction solvent by HPLC-UV. The influence of the mass of MIL, extraction time, salt concentration, and the pH of the sample solution was investigated to obtain optimized extraction efficiency. Besides, extraction conditions including salt concentration, mass of MIL and extraction time were further optimized by the Box-Behnken design through the response surface method. Under optimized conditions, the limits of detection (LODs) of all estrogens were ranged from 5 ng mL^-1 to 15 ng mL^-1. The recoveries ranging from 98.5% to 109.3% in milk and from 96.3% to 111.4% in cosmetics were also studied, respectively. Furthermore, the proposed method were statistically compared with the reported conventional IL-DLLME method and the National standard methods of food safety and cosmetics. The experimental results showed that the functionalized MIL could successfully applied for extraction, separation and pretreatment of estrogens in milk and cosmetics.

Mesoporous Ionically Tagged Cross-Linked Poly(vinyl imidazole)s as Novel and Reusable Catalysts for the Preparation of N-Heterocycle Spiropyrans

Herein, two novel mesoporous cross-linked poly(vinyl imidazole)s with sulfonic acid tags, [PVI-SO3H]Cl (1) and [PVI-SO3H]FeCl4 (2), were prepared and characterized by a variety of techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy, elemental mapping, energy dispersive X-ray analysis, transmission electron microscopy, thermal gravimetry, derivative thermal gravimetry, and N2 adsorption-desorption isotherms (Brunauer-Emmett-Teller). In addition, magnetic properties of poly(vinyl imidazole) sulfonic acid iron(IV) chloride [PVI-SO3H]FeCl4 (2) as an ionically tagged magnetic polymer were investigated using a vibrating sample magnetometer. The presented polymers, [PVI-SO3H]Cl (1) and [PVI-SO3H]FeCl4 (2), were successfully applied as reusable and efficient catalysts for the preparation of N-heterocycle spiropyrans. The described catalysts were recycled and reused with a marginal decrease in their catalytic activities. The desired products were prepared under mild and green conditions. The structures of the obtained products were confirmed by various analysis techniques.

Novel Ionic Liquid-Functionalized Chitosan [DSIM][AlCl3] x -@CS: Synthesis, Characterization, and Catalytic Application for Preparation of Substituted Pyrazine Derivatives

Pyrazines are renowned heterocyclic compounds that have played an important role in drug design and are part of many polycyclic compounds of biological and industrial significance. In this article, a novel chitosan-immobilized ionic liquid, [DSIM][AlCl₃] _x ^-@CS, has been synthesized easily at ambient temperature and used for catalyzing the synthesis of a series of biologically relevant pyrazine derivatives. The catalyst is well characterized by various techniques such as Fourier transform infrared spectroscopy, Raman spectroscopy, solid-state ¹³C MAS nuclear magnetic resonance, scanning electron microscopy/energy-dispersive X-ray, elemental mapping, transmission electron microscopy, powder X-ray diffraction, and thermal gravimetric analyses. The advantageous features of the present energy-sustainable methodology include high yield of product (>99%), shorter reaction time periods, and recyclability of the catalyst.

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

This review article discusses the progress related to the synthesis and catalytic applications of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials for industrial and laboratory products. These catalysts are widely used in acid-catalyzed processes. Most of these acid catalysts are eco-friendly, reusable, and stable. Moreover, the discovery of unique catalysts is vital for developing new, efficient, and reusable catalysts for industrial and laboratory applications. The aim of this review article is to review the recent studies (2014-2018) in the field of the utility of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials for developing acidic catalysts.

1,3-Disulfoimidazolium chloronickellate immobilized HZSM-5 framework as visible-light-induced heterogeneous photocatalyst for advanced oxidation process

Hybrid photocatalysts of [Dsim]₂[NiCl₄]/HZSM-5 were prepared by wet impregnation and their application is demonstrated as feasible heterogeneous photocatalysts for oxidative degradation of methylene blue under sunlight.