Choline chloride·2ZnCl2 ionic liquid: an efficient and reusable catalyst for the solvent free Kabachnik–Fields reaction

Deep Eutectic Solvents: The Organic Reaction Medium of the Century

“…Deep eutectic solvents have been used as sustainable media, as well as catalysts, in different multicomponent reactions, with the most successful constituent being choline chloride (ChCl). In particular, deep eutectic solvents based on choline chloride and metal chlorides have been used in the synthesis of dihydropyrimidinone derivatives through the Biginelli reaction, [63] as well as in the preparation of functionalized amines, such as -aminoketones [64] and -aminophosphonates [65] through multicomponent reactions. Thus, the Biginelli reaction using a mixture of choline chloride-tin(II) chloride (1:2 molar ratio) as catalyst and reaction media has been used in the synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives (Scheme 12).…”

“…[65] The reaction, which under conventional conditions requires toxic metal catalysts, long reaction times, and the foul smelling triethyl phosphite as reagent, allows the preparation of the target compounds in good yields and very short reaction times at room temperature, as depicted in Scheme 13. Furthermore, the DES was easily recycled and reused for five cycles.…”

Zinc (II) chloride-based deep eutectic solvents for application as electrolytes: Preparation and characterization

“…Despite carrying out the reaction in far shorter time with higher yields over 95% compared to the other alternatives, it is noticeable that ZnCl 2 -based catalysts were recycled by simple extraction from the reaction mixture. The viscous eutectic mixtures that remained in the reaction flask were thoroughly washed with ether and reused in subsequent reactions without further purifications [16]. Add to this, ChCl:CuCl DESs became attractive homogeneous catalysts in view of their ease of applications and low costs in the palladium-free Sonogashira-type cross-coupling reactions.…”

Organic Synthesis without Conventional Solvents

“…Especially ChCl-ZnCl 2 (1:2) was used extensively, for example in esterification, [138] the Biginelli reaction, [139] the Kabachnik-Fields reaction, [140] the Fischer Indole synthesis, [141] the acetylation of monosaccharides, [142] the Friedel-Craft-Acylation [143] and alkylation, [144] the Mannich reaction, [145] the synthesis of aromatic amides, [146] and the Diels-Alder reaction. Especially ChCl-ZnCl 2 (1:2) was used extensively, for example in esterification, [138] the Biginelli reaction, [139] the Kabachnik-Fields reaction, [140] the Fischer Indole synthesis, [141] the acetylation of monosaccharides, [142] the Friedel-Craft-Acylation [143] and alkylation, [144] the Mannich reaction, [145] the synthesis of aromatic amides, [146] and the Diels-Alder reaction.…”