One-pot four-component synthesis of highly substituted pyrroles in gluconic acid aqueous solution

Eucalyptol, an All-Purpose Product

Eucalyptus plants have attracted the attention of researchers and environmentalists worldwide because they are a rapidly growing source of wood and a source of oil used for multiple purposes. The main and the most important oil component is 1,8-cineole (eucalyptol: 60–85%). This review summarizes the literature reported to date involving the use of 1,8-cineole for the treatment of disorders. Additionally, we describe our efforts in the use of eucalyptol as a solvent for the synthesis of O,S,N-heterocycles. Solvents used in chemistry are a fundamental element of the environmental performance of processes in corporate and academic laboratories. Their influence on costs, safety and health cannot be neglected. Green solvents such as bio-based systems hold considerable additional promise to reduce the environmental impact of organic chemistry. The first section outlines the process leading to our discovery of an unprecedented solvent and its validation in the first coupling reactions. This section continues with the description of its properties and characteristics and its reuse as reported in the various studies conducted. The second section highlights the use of eucalyptol in a series of coupling reactions (i.e., Suzuki–Miyaura, Sonogashira–Hagihara, Buchwald–Hartwig, Migita–Kosugi–Stille, Hiyama and cyanation) that form O,S,N-heterocycles. We describe the optimization process applied to reach the ideal conditions. We also show that eucalyptol can be a good alternative to build heterocycles that contain oxygen, sulfur and nitrogen. These studies allowed us to demonstrate the viability and potential that bio solvents can have in synthesis laboratories.

Revisit to the synthesis of 1,2,3,4-tetrasubstituted pyrrole derivatives in lactic acid media as a green solvent and catalyst

In this study, for the first time, lactic acid was used as a bio-based green catalyst and reaction medium for the synthesis of 1,2,3,4-tetrasubstituted pyrrole derivatives from one-pot three-component reaction of commercially available primary amines, 1,3-dicarbonyl compounds, and trans-β-nitrostyrene at room temperature. Thirty-three corresponding pyrroles, of which eight are novel and have been reported for the first time, were synthesized in high to excellent yields in lactic acid media and characterized by spectroscopic analysis. In all examined cases, lactic acid represented many advantages, including shorter reaction time, ease of product isolation, higher yields, no by-products, no chromatographic process, and lower volatility in the reaction. This bio-based green solvent can also be recycled and reused three times without loss of its efficiency as a catalyst and solvent.

Greener Synthesis of Nitrogen-Containing Heterocycles in Water, PEG, and Bio-Based Solvents

The solvents used in chemistry are a fundamental element of the environmental performance of processes in corporate and academic laboratories. Their influence on costs, health safety, and nature cannot be neglected. Quantitatively, solvents are the most abundant constituents of chemical transformations; therefore, acting on solvents and replacing standard solvents with safer products can have a great ecological impact. However, not all green solvents are suitable for the wide scope of organic chemistry reactions. A second point to consider is that 50% of pharmaceutical drugs are nitrogen heterocycles compounds. It therefore appeared important to provide an overview of the more ecological methodologies for synthesizing this class of compounds. In this review, all publications since 2000 that describe green reactions leading to the formation of nitrogen heterocycles using safe solvents were considered. We chose water, PEG, and bio-based solvents for their negligible toxicity. The synthesis of five-, six-, and seven-membered aromatic nitrogen heterocycles using green reactions reported in the literature to date is described.

Eco-friendly polyethylene glycol (PEG-400): a green reaction medium for one-pot, four-component synthesis of novel asymmetrical bis-spirooxindole derivatives at room temperature

PEG-400 has been used as a green and biodegradable polymeric solvent for the one-pot, two-step, multi-component synthesis of novel asymmetrical bis-spirooxindole derivatives by the reaction of N-alkyl isatin, isatin derivatives, alkylmalonates and C–H activated carbonyl compounds in the presence of K₂CO₃ at room temperature. Using this procedure, all the products were obtained in good to excellent yields.

PEG-400 has been used for the synthesis of novel asymmetrical bis-spirooxindoles by the reaction of N-alkyl isatin, isatin derivatives, alkylmalonates and C–H activated carbonyl compounds in the presence of K₂CO₃ at room temperature.

FeCl3-Mediated Domino Reaction of Benzoxazinones with Aroylmethylidene Malonates: Synthesis to Functionalized Pyrrolobenzoxazines

An efficient domino approach for the synthesis of pyrrolobenzoxazine derivatives is described. The FeCl₃-promoted domino reaction between aroylmethylidene malonates and benzoxazinones has been successfully established to afford the title compounds in good to excellent yield under mild reaction conditions. The domino protocol provides a concise and straightforward access to highly substituted pyrrolobenzoxazines with high efficiency and excellent functional group tolerance.

A magnetic metal–organic framework as a highly active heterogeneous catalyst for one-pot synthesis of 2-substituted alkyl and aryl(indolyl)kojic acid derivatives

A novel magnetic metal–organic framework, NiFe₂O₄@MOF-5, was prepared and demonstrated to be a highly efficient catalyst for the one-pot three-component reaction of aldehyde, indole, and kojic acid.

Magnetically separable graphene oxide anchored sulfonic acid: a novel, highly efficient and recyclable catalyst for one-pot synthesis of 3,6-di(pyridin-3-yl)-1H-pyrazolo[3,4-b]pyridine-5-carbonitriles in deep eutectic solvent under microwave irradiation

A magnetic separable sulfonic acid catalyst was prepared and applied for the synthesis of 3,6-di(pyridin-3-yl)-1H-pyrazolo[3,4-b]pyridine-5-carbonitriles via three-component reaction of 1-phenyl-3-(pyridin-3-yl)-1H-pyrazol-5-amine, β-ketonitrile and aldehydes in DES.

Active methylenes in the synthesis of a pyrrole motif: an imperative structural unit of pharmaceuticals, natural products and optoelectronic materials

Pyrrole is one of the most important azaheterocycles, due to its wide range of applications in pharmaceuticals and optoelectronic materials, coupled with its utility as an intermediate in natural products.

A one-pot sequential five-component domino reaction for the expedient synthesis of polysubstituted pyrroles

A new protocol towards the synthesis of polysubstituted pyrroles via enaminone from one-pot five-component reactions under catalyst free conditions.

Lactic acid as an invaluable green solvent for ultrasound-assisted scalable synthesis of pyrrole derivatives

Lactic acid has been used as a bio-based green solvent to study the ultrasound-assisted scale-up synthesis. We report here, for the first time, on the novel and scalable process for synthesis of pyrrole derivatives in lactic acid solvent under ultrasonic radiation. Eighteen pyrrole derivatives have been synthesized in lactic acid solvent under ultrasonic radiation and characterized by (1)H NMR, IR, ESI MS. The results show, under ultrasonic radiation, lactic acid solvent can overcome the scale-up challenges and exhibited many advantages, such as bio-based origin, shorter reaction time, lower volatility, higher yields, and ease of isolating the products.

Recent advances in the synthesis of pyrroles by multicomponent reactions

Pyrrole is one of the most important one-ring heterocycles. The ready availability of suitably substituted and functionalized pyrrole derivatives is essential for the progress of many branches of science, including biology and materials science. Access to this key heterocycle by multicomponent routes is particularly attractive in terms of synthetic efficiency, and also from the environmental point of view. We update here our previous review on this topic by describing the progress made in this area in the period between mid-2009 and the end of 2013.

Meglumine catalyzed one-pot, three-component combinatorial synthesis of pyrazoles bearing a coumarin unit

Meglumine has been found to be an efficient catalyst for the synthesis of pyrazolylcoumarins by one-pot three-component reaction of salicylaldehyde, 4-hydroxy-6-methyl-2H-pyran-2-one, and hydrazine.