Li-Ping Mo

Recent advances in the application of deep eutectic solvents as sustainable media as well as catalysts in organic reactions

Deep eutectic solvents (DESs), also known as deep eutectic ionic liquids (DEILs) or low-melting mixtures (LMMs) or low transition temperature mixtures (LTTMs) in the literature, have become more and more attractive in recent years due to their interesting properties and benefits, such as low cost of components, easy to prepare, tunable physicochemical properties, negligible vapor pressure, non-toxicity, biorenewability and biodegradability. These eutectic mixtures have been widely used as green and sustainable media as well as catalysts in many chemical processes. This review focuses on recent advances using DESs in organic reactions including addition reactions, cyclization reactions, replacement reactions, multicomponent reactions, condensation reactions, oxidation reactions, and reducing reactions.

Sulfonic acid supported on hydroxyapatite-encapsulated-γ-Fe2O3 nanocrystallites as a magnetically separable catalyst for one-pot reductive amination of carbonyl compounds

A novel, environmentally friendly procedure has been developed for the preparation of secondary or tertiary amines by one-pot reductive amination of carbonyl compounds using sodium borohydride in the presence of a magnetically recoverable sulfonic acid supported on hydroxyapatite-encapsulated-γ-Fe2O3 [γ-Fe2O3@HAP-SO3H] at room temperature. The catalyst was easily separated from the reaction mixture by applying an external magnet and reused for six cycles without significant loss of catalytic activity.

Catalyst-free synthesis of quinazoline derivatives using low melting sugar–urea–salt mixture as a solvent

Low melting mixture of maltose–dimethylurea (DMU)–NH4Cl was found to be an inexpensive, non-toxic, easily biodegradable and effective reaction medium in the catalyst-free synthesis of quinazoline derivatives. This simple and efficient method furnished the corresponding quinazolines in high yields via one-pot three-component reaction of 2-aminoaryl ketones, aldehyde, and ammonium acetate under aerobic oxidation conditions.

One-pot, three-component synthesis of a library of spirooxindole-pyrimidines catalyzed by magnetic nanoparticle supported dodecyl benzenesulfonic acid in aqueous media.

Dodecyl benzenesulfonic acid functionalized silica-coated magnetic nanoparticles (γ-Fe2O3@SiO2-DDBSA) were readily prepared and identified as an efficient catalyst for the synthesis of a library of spirooxindole-pyrimidine derivatives by three-component condensation reaction of barbituric acids, isatins and cyclohexane-1,3-diones. The aqueous reaction medium, easy recovery of the catalyst using an external magnet, and high yields make the protocol sustainable and economic.

Superparamagnetic CuFeO2 Nanoparticles in Deep Eutectic Solvent: an Efficient and Recyclable Catalytic System for the Synthesis of Imidazo[1,2‐a]pyridines

Superparamagnetic CuFeO2 nanoparticles were prepared and characterized by XRD, SEM, TEM, FRIR spectroscopy, and vibrating sample magnetometry techniques. The catalytic activity of CuFeO2 nanoparticles was investigated in the one‐pot, three‐component reaction of 2‐aminopyridines, aldehydes, and alkynes using citric acid–dimethylurea melt as a green solvent. An array of imidazo[1,2‐a]pyridines were obtained in good to excellent yields. The catalytic system can be successfully reused six times with keeping its catalytic performance.

Nano CoFe2O4 supported antimony(III) as an efficient and recyclable catalyst for one-pot three-component synthesis of multisubstituted pyrroles

A novel magnetic nano-CoFe2O4 supported Sb ([CoFe2O4@SiO2–DABCO–Sb]) was successfully constructed, which exhibited high catalytic activity for one-pot three-component synthesis of multisubstituted pyrroles in the reaction of amines, nitroolefin and 1,3-dicarbonyl compounds. The magnetic heterogeneous catalyst could be easily recovered using an external magnet and reused many times without significant loss of catalytic activity.

Meglumine catalyzed expeditious four-component domino protocol for synthesis of pyrazolopyranopyrimidines in aqueous medium

A facile and highly efficient protocol for the one-pot, four-component reaction of ethyl acetoacetate, hydrazine hydrate, aromatic aldehydes and barbituric acid has been developed using meglumine as an inexpensive, biodegradable and reusable catalyst. This methodology provides a mild and fast route to structurally diverse tricyclic fused pyrazolopyranopyrimidines in good to excellent yields. Simplicity, room temperature reaction conditions, a green solvent, an easy work-up process, inexpensive price and reusability of the catalyst are the main advantages of this method.

One-pot three-component synthesis of 1,2,3-triazoles using magnetic NiFe2O4–glutamate–Cu as an efficient heterogeneous catalyst in water

A novel magnetic NiFe2O4 supported glutamate–copper catalyst was prepared in a convenient and ecofriendly manner and characterized using FTIR, XRD, EDX, TEM, SEM, XPS and VSM. This magnetic catalyst exhibited excellent catalytic activity for the synthesis of a wide variety of 1,4-disubstituted-1,2,3-triazoles via one-pot three-component click reactions of sodium azide, non-activated terminal alkynes, and different azide precursors such as epoxides, benzyl chlorides, and aryl boronic acids at room temperature in water. This procedure has some advantages such as an aqueous reaction medium, ambient reaction conditions, high yields, wide substrate scope, easy separation of the catalyst using an external magnet and efficient recycling.

A mild and practical procedure for synthesis of substituted 2-aminobenzophenones

A convenient three-step procedure has been developed for synthesis of substituted 2-aminobenzophenones from substituted anilines. The anilines are first protected as acetanilides, by reaction with acetic anhydride. These are then benzoylated with (trichloromethyl)benzene in the presence of aluminium-generated 2-acetamidobenzophenone. Finally, removal of the acetyl group from the amino group provides the substituted 2-aminobenzophenones in moderate to good yields.

A green approach for synthesis of naphthoquinone-fused oxazine derivatives in water under ultrasonic irradiation

An efficient and eco-friendly procedure has been developed for synthesis of naphthoquinone-fused oxazine derivatives via one-pot pseudo four-component reaction of 2-hydroxy-1,4-naphthoquinone, aromatic amine and formaldehyde in water under ultrasound irradiation. This protocol has the advantages of being catalyst-free, with short reaction times and high yields, and being environmentally benign with an easy work-up.