Palladium Mesoionic Carbene Pre-catalyst for General Cross-Coupling Transformations in Deep Eutectic Solvents

Abstract

A strong σ-donor mesoionic carbene ligand has been synthesized and applied to four different palladium-catalyzed cross-coupling transformations, proving the catalyst/medium compatibility and the increased activity of this system over previous reports in Deep Eutectic Solvent medium. Some cross-coupling processes could be carried out at room temperature and using aryl chlorides as starting materials. The possible implementation of multistep synthesis in eutectic mixtures has also been explored. The presence of palladium nanoparticles in the reaction media has been evaluated and correlated to the observed activity.

Deep Eutectic Solvents in Solar Energy Technologies

“…All of these exceptional features, combined with the low cost of components, easiness of preparation with high purity, high biodegradability and low toxicity, have made DESs attractive and promising as a new generation of nonaqueous solvents/cosolvents for a broad range of applications in organic synthesis [ 24 , 25 , 26 ], main group chemistry [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ], metal-, bio-, and organo-catalysis [ 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 ], dissolution and extraction processes [ 54 , 55 , 56 , 57 , 58 ], electrochemistry [ 59 , 60 ], material chemistry [ 61 , 62 ], photosynthesis [ 63 ], and even protein crystallization [ 64 ].…”

Sustainable Ligand‐Free Heterogeneous Palladium‐Catalyzed Sonogashira Cross‐Coupling Reaction in Deep Eutectic Solvents

“…Most DESs are easily available from renewable feedstocks, and thus they are extraordinarily biodegradable and non‐toxic . To the best of our knowledge, there are only a few works related to the use of DESs/low melting mixtures (LMMs) in SH coupling reactions: (a) in 2009, König and Ilgen described the use of a D‐mannose/urea LMM to promote cross‐coupling between phenylacetylene and two aryl halides using PdCl 2 (PPh 3 ) 2 as an homogeneous catalyst (Scheme a); (b) in 2010, Fuxiang and coworkers reported the CuI‐mediated cross‐coupling between aryl iodides and 4‐propylphenylacetylene, catalyzed by in situ prepared Pd(Ph 3 P) 4 , using the binary Bu 4 NCl/imidazole (1 : 3) eutectic mixture (Scheme b); (c) between 2017 and 2019, Ramón, Alonso, Guillena and co‐workers mainly investigated the cross‐coupling between phenylacetylene and several (hetero)aryl halides either in a Ph 3 PMeBr/Gly (1 : 2)‐based eutectic mixture using cationic pyridiniophosphine ligands associated to the catalyst PdCl 2 or in a AcChCl/urea (1 : 2) as reaction medium by exploiting the strong σ‐donor ability of a mesoionic carbene ligand to enhance the propensity of Pd to undergo oxidative addition (Scheme c) …”

Deep Eutectic Solvents as Effective Reaction Media for the Synthesis of 2-Hydroxyphenylbenzimidazole-Based Scaffolds en Route to Donepezil-Like Compounds

“…Because of their ability to act also as catalysts and reagents [29,30], DESs have been primarily investigated in extraction and separation processes [31][32][33][34], in material sciences [35], for metal electrodeposition [36], and for the synthesis of heterocycles [37]. Emerging and hot fields of applications are represented by organometallics [38][39][40], metal- [41][42][43][44][45][46][47][48], bio- [49][50][51][52][53], and organo-catalysis [54][55][56][57], electrochemistry [58], photosynthesis [59] and energy technology [60,61]. Building upon our interests in the synthesis of drugs and heterocycles using eco-friendly reaction media like DESs [43][44][45][46][47]55,62,63] and water [64], herein we report the sustainable preparation of several 2-hydroxyphenylbenzimidazole derivatives and the whole synthesis of PZ1 [19] in selected eutectic mixtures.…”