Reusable proline-based ionic liquid catalyst for the simple synthesis of 2-arylbenzothiazoles in a biomass medium

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.

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.

Nano-kaolin/Ti4+/Fe3O4: a magnetic reusable nano-catalyst for the synthesis of pyrimido[2,1-b]benzothiazoles

Herein, nano-kaolin/Ti⁴⁺/Fe₃O₄ as a new magnetic nano-catalyst was synthesized, and its structural properties were characterized using various techniques such as Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), a vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA) and energy-dispersive X-ray spectroscopy (EDX). This catalyst was used for the synthesis of pyrimido[2,1-b]benzothiazoles via the one-pot condensation of 2-aminobenzothiazole, an aldehyde and β-keto ester under solvent-free conditions at 100 °C. This simple protocol has many advantages such as easy workup, high product yields, short reaction times and reusability of the catalyst.

Herein, nano-kaolin/Ti⁴⁺/Fe₃O₄ as a new magnetic nano-catalyst was synthesized, and its structural properties were characterized using various techniques such as FTIR spectroscopy, FE-SEM, TEM, XRD, VSM, TGA and EDX.