Unraveling the Potential Role of Deep Eutectic Solvents (DESs): Synthesis of Ketazines & Pyrazolines

Abstract

Increasing demand to curtail the usage of hazardous organic solvents, reagents and/or catalysts, has engrossed the interest of the scientific community towards the development of next generation liquid media, commonly known as the ‘deep eutectic solvents’ (DESs). Bearing the significant role of ketazine and pyrazoline derivatives in mind, herein, after screening various DESs for the condensation of ketones and hydrazine followed by the cyclization to produce corresponding pyrazolines, a low melting mixture of citric acid: N,N‐dimethyl urea (CA:DMU) in 2 : 3 ratio was found to be the best choice for this particular transformation. Interestingly, the DESs was recycled easily and reused up to four times without affecting the yield of the product to a greater extent. Hopefully, this method may be useful to generate different kinds of valuable ketazines as well as pyrazoline derivatives of particular interest in years to come.

Strategies and Methods for the Synthesis of 2‐Pyrazolines: Recent Developments (2012–2022)

“…During the optimization experiments, the authors screened many deep eutectic solvents (DES) to develop an eco‐friendly protocol, and, while most of them gave moderate to good or comparable results, the aforementioned pair proved to be the most efficient. Interestingly, the same reaction at a lower temperature (70 °C instead of 100 °C) and shorter reaction time (2 h instead of 6 h) yielded the corresponding ketazines [107] . Pyrazolines prepared with this method were purified by column chromatography.…”

“…A few years afterwards, the same group reported two methodologies involving the alkaline reagent diethylzinc 111, that enabled the deprotonation of CF 3 CHN 2 (107) to generate in-situ zinc trifluorodiazoethylidene 112. The first application involved the preparation of complex trifluoromethylated polycyclic pyrazolines 114 a and 114 b via a [3 + 2]-cycloaddition reaction with α,β-unsaturated enones 113.…”

“…Interestingly, the same reaction at a lower temperature (70 °C instead of 100 °C) and shorter reaction time (2 h instead of 6 h) yielded the corresponding ketazines. [107] Pyrazolines prepared with this method were purified by column chromatography.…”

Facile synthesis and anion binding studies of fluorescein/benzo-12-crown-4 ether based bis-dipyrromethane (DPM) receptors

“…11–19 But, we believe that, there is still a pressing necessity to develop simple-to-make yet highly sensitive and selective anion receptors. 20–30…”

A Facile Deep Eutectic Solvent (DES) Mediated Green Approach for the Synthesis of Fluorescein and Phenolphthalein Dyes

“…Keeping the astonishing assets of DESs in consideration, and also as our central goal to construct diverse organic as well as supramolecular scaffolds under green conditions, [64–70] here we have successfully developed a novel green protocol to assemble two important dyes, fluorescein and phenolphthalein from commercially available phthalic anhydride and resorcinol/phenol using a DES of ChCl/ZnCl 2 (1 : 2). As far as our knowledge is concerned, this is the first‐ever method for the preparation of fluorescein and phenolphthalein dye molecules under green conditions involving DESs.…”