Recent Progress in Three-Component Reactions. An Update

Solvent-Free, One-Pot, Multicomponent Synthesis of Xanthene Derivatives

An efficient and environmentally benign one-pot condensation of cyclic diketones, aldehydes and naphthols was achieved with 1,4-diazabicyclo[2-2-2]octane supported on Amberlyst-15 as a novel catalyst, producing a variety of benzoxanthenones in good to excellent yields. The advantages of this multicomponent reaction include the use of a heterogeneous catalyst, solventless conditions and a simple methodology that is atom-economical and results in low E-factor values. A total of 17 xanthene derivatives, including two novel molecules, were synthesized and then characterized. Aromatic aldehydes carrying an electron-withdrawing group provided excellent yields. Appreciable results were also obtained using aliphatic aldehydes. The catalyst is fully recyclable and can be reused up to six times.

Stabilization of copper nanoparticles onto the double Schiff-base-functionalized ZSM-5 for A3 coupling reaction catalysis aimed under mild conditions

In this research a highly efficient and heterogeneous catalyst of ZSM-5@APTMS@(E)-4-((pyridin-2-ylimino)methyl) benzaldehyde@Cu-NPs was synthesized for upgrading the A³ coupling reaction for the synthesis of propargylamines under mild conditions. Rational tuning of the microenvironment of metallic NPs to improve efficiency and reusability in catalytic performances is of significance for scalable applications. Firstly, ZSM-5 was immobilized with APTMS (3-aminopropyltrimethoxysilane) and further modified with (E)-4-((pyridin-2-ylimino)methyl)benzaldehyde. Subsequently, the amine-activated zeolite@(E)-4-((pyridin-2-ylimino)methyl)benzaldehyde was applied to increase the stabilization of Cu metal nanoparticles. The catalyst was treated with hydrazine to reduce Cu(ii) to Cu(0), which led to active metal sites. The results of catalytic performance in comparison with different parts of catalysis indicate high efficiency due to the stabilization of copper nanoparticles onto the newly synthesized support of MOF modified with nitrogen aromatic groups. The addition of N-rich organic ligand through modification alters the electronic structure of the final composite in favor of the progress of the A³-coupling reaction. Moreover, the proposed catalyst showed no reduction in the catalytic performance up to four cycles, and a minor loss of efficiency occurs after the seventh cycle. In addition, the catalyst was effectively recycled up to 7 times without leaching of Cu-NPs.

High-component reactions (HCRs): An overview of MCRs containing seven or more components as versatile tools in organic synthesis

Recently, multi-component reactions (MCRs) have gained special attention due to their versatility for the synthesis of polycyclic heterocycles. Moreover, their applicability can become more widespread as they can be combined together as a union of MCRs. In this overview, the authors have tried to collect the MCRs containing more than seven components that can lead to effectual heterocycles in organic and/or pharmaceutical chemistry. The review contains papers published up to the end of 2020. The subject is classified based on the number of substrates, such as seven-, eight-, nine-, ten-, and more components. The authors expect their report to be helpful for researchers to clarify their route to significant MCRs.

The Ugi three-component reaction and its variants

A broad variety of α-aminoamide-based compounds have been synthesized via the three-component version of the Ugi reaction (U-3CR) or by any of its variants (Ugi-Zhu-3CR, Orru-3CR, Ugi-4C-3CR, Ugi-Joullié-3CR, GBB-3CR, Ugi-Reissert-3CR, and so on).

Direct Asymmetric Three-Component Mannich Reaction Catalyzed by Chiral Counteranion-Assisted Silver

Direct asymmetric three-component Mannich reaction involving simple ketones (such as cyclohexanone, acetone, and acetophenone) as donors and catalyzing by silver tartaric acid-derived phosphate was realized to afford a series of optically active β-amino-ketone derivatives in high yields (up to 96%) and good-to-high enantioselectivities (up to 97%) with moderate-to-good diastereoselectivities. This is the first example of direct catalytic asymmetric three-component Mannich reaction via a chiral counteranion-directed strategy.

Novel Biomass Derived from Grape Pomace Waste as an Efficient Nanocatalyst for the Synthesis of Dibenzoxanthene, Tetraketone, bis(indolyl)alkane and Chromene Derivatives and their Antimicrobial Evaluation

BACKGROUND

Sulfonated carbon-based solid acids (CBSAs) have been reported as an efficient solid acid catalyst for many acid-catalyzed reactions. Furthermore, the use of carbon obtained from biomass waste has been explored and these materials showed a higher catalytic performance and higher stability compared to other solid acids.

OBJECTIVE

Novel biomass carbon-based solid acids nanoparticles with high catalytic activity in organic transformation, such as Grape pomace waste-SO3H Nanoparticles (GPW-SO3H NPs), were successfully synthesized.

MATERIALS AND METHODS

Grape pomace waste-SO3H Nanoparticles (GPW-SO3H NPs) were successfully synthesized. The grape pomace waste was dried in an oven at a temperature of 70°C and crushed to powder using an electric spice grinder. A mixture of powdered grape pomace waste (1 g) and concentrated sulfuric acid (>98%, 10 mL) was stirred at room temperature. Then, the resultant mixture was transferred into a 100 mL sealed Teflon-lined autoclave and kept at 180°C for 12 h. After cooling to room temperature, the resulting black solid was dried at 100°C in an oven under vacuum and the sulfonic acid-functionalized magnetic nanoparticles (Fe3O4@C-SO3H) were obtained.

RESULTS AND DISCUSSIONS

The catalytic activity of GPW-SO3H was assessed through an easy and rapid protocol developed for the one-pot synthesis of 14-aryl-14-H-dibenzo [a,j]xanthene, arylmethylene [bis(3- hydroxy-2-cyclohexene-1-one)], bis(indolyl)alkane and 2-amino-4-aryl-7-hydroxy-4H-chromene-3-carbonitrile derivatives in excellent yields. The advantages of this method include use of waste material for catalyst synthesis, high yields, mild reaction conditions, uncomplicated work-up procedures, neutral conditions, and recoverable catalyst.

CONCLUSION

We have shown that biomass-derived solid acids, prepared from grape pomace waste, serve as a non-toxic, inexpensive and a promising eco-friendly and novel carbon-based solid acid nanocatalyst for organic transformations.

Metal and Non-Metal Catalysts in the Synthesis of Five-Membered S-Heterocycles

BACKGROUND

A wide variety of biological activities are exhibited by N, O and S containing heterocycles and recently, many reports appeared for the synthesis of these heterocycles. The synthesis of heterocycles with the help of metal and non-metal catalyst has become a highly rewarding and important method in organic synthesis. This review article concentrated on the synthesis of S-heterocylces in the presence of metal and non-metal catalyst. The synthesis of five-membered S-heterocycles is described here.

OBJECTIVE

There is a need for the development of rapid, efficient and versatile strategy for the synthesis of heterocyclic rings. Metal, non-metal and organocatalysis involving methods have gained prominence because traditional conditions have disadvantages such as long reaction times, harsh conditions and limited substrate scope.

CONCLUSION

The metal-, non-metal-, and organocatalyst assisted organic synthesis is a highly dynamic research field. For ßthe chemoselective and efficient synthesis of heterocyclic molecules, this protocol has emerged as a powerful route. Various methodologies in the past few years have been pointed out to pursue more sustainable, efficient and environmentally benign procedures and products. Among these processes, the development of new protocols (catalysis), which avoided the use of toxic reagents, are the focus of intense research.

A Microwave Accelerated Sustainable Approach for the Synthesis of 2-amino-4H-chromenes Catalysed by WEPPA: A Green Strategy

Background:

The agricultural wastes as a source offer an excellent alternative to replace many toxic and environmentally hazardous catalysts, due to their least toxicity, ease of biodegradability, and ability to act as a greener catalytic medium. Some of the agro-waste based catalysts reported are BFE, WERSA, WEB, and WEPBA. 2-Amino-4H-chromene derivatives are promising biologically potent heterocyclic compounds, due to their medicinal applications such as antimicrobial, anti-inflammatory, antibacterial, antiviral, anticancer, antidiuretic, anticoagulant and antianaphylactic activities. The present work describes a microwave accelerated, efficient, eco-friendly and economical approach for the synthesis of 2-amino-4H-chromenes through condensation of substituted arylaldehyde, malononitrile and resorcinol/naphthol catalyzed water extract of pomegranate peel ash (WEPPA) under microwave irradiation. The reaction completed within 3-6 min with good to excellent yield of product isolation. The final product isolated by simple filtration and recrystallization gave a spectroscopically pure form of product and did not require further purification.

Methods:

The pomegranate peel ash water extract as an agro-waste derived catalyst was employed under microwave irradiation for the economical synthesis of 2-amino-4H-chromene derivatives.

Results:

The reported agro-waste based catalyst was obtained in the absence of external base, additives and solvent-free synthesis of 2-amino-4H-chromene using aryl aldehyde, malononitrile and resorcinol/ naphthol under microwave irradiation. WEPPA acts as a solvent media and catalyst, as it plays a dual role in the synthesis of 2-amino-4H-chromenes.

Conclusion:

We established an efficient, simple, agro-waste based catalytic approach for the synthesis of 2-amino-4H-chromene derivatives from the condensation of arylaldehyde, malononitrile and resorcinol/α-naphthol/β-naphthol employing WEPPA as an efficient catalyst under microwave synthesis. The method has found to be a greener, economic and eco-friendly approach for the synthesis of chromene scaffolds. The advantages of the present approach are solvent-free, no external metal, chemical base free, short reaction time and isolated product in good to excellent yields. The catalyst is agro-waste derived, which has abundant natural sources available, thus making the present approach a greener one.

Reactivity and Synthetic Applications of Multicomponent Petasis Reactions

The Petasis boron-Mannich reaction, simply referred to as the Petasis reaction, is a powerful multicomponent coupling reaction of a boronic acid, an amine, and a carbonyl derivative. Highly functionalized amines with multiple stereogenic centers can be efficiently accessed via the Petasis reaction with high levels of both diastereoselectivity and enantioselectivity. By drawing attention to examples reported in the past 8 years, this Review demonstrates the breadth of the reactivity and synthetic applications of Petasis reactions in several frontiers: the expansion of the substrate scope in the classic three-component process; nonclassic Petasis reactions with additional components; Petasis-type reactions with noncanonical substrates, mechanism, and products; new asymmetric versions assisted by chiral catalysts; combinations with a secondary or tertiary transformation in a cascade- or sequence-specific manner to access structurally complex, natural-product-like heterocycles; and the synthesis of polyhydroxy alkaloids and biologically interesting molecules.