Reshaping Ullmann Amine Synthesis in Deep Eutectic Solvents: A Mild Approach for Cu-Catalyzed C–N Coupling Reactions With No Additional Ligands

Abstract

The CuI-catalyzed Ullmann amine cross-coupling between (hetero)aryl halides (Br, I) and aromatic and aliphatic amines has been accomplished in deep eutectic solvents as environmentally benign and recycling reaction media. Under optimized conditions, the reaction proceeds smoothly under mild conditions (60–100°C) in air, in the absence of ligands, with a catalyst (CuI) loading of 10 mol% and K2CO3 (aliphatic primary and secondary amines) or t-BuOK (aromatic amines) as the base. A variety of amines have been synthesized in yields up to 98% with a broad substrate scope.

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

“…A notable exception is represented by the employment of γ‐valerolactone as an alternative, non‐toxic biomass‐derived medium solvent for synthesizing acetylene‐containing systems starting from (hetero)aryl iodides . Based on our ongoing interest in using water and DESs to explore novel paradigms in metal‐mediated and metal‐catalyzed organic transformations, herein we report the results of a study demonstrating the usefulness of a recycling biocompatible DES such as ChCl/Gly as an environmentally responsible reaction medium for carrying out ligand‐free SH couplings between (hetero)aryl iodides and terminal aryl‐ or alkyl‐substituted alkynes with a broad substrate scope, and working under heterogeneous conditions by using a cheap and recyclable catalyst such as Pd/C (Scheme d).…”

“…The solvent remains an important and active component of heterogeneously Pd‐catalyzed cross‐coupling reactions: the reactants must diffuse through the medium to approach the catalyst and the medium, in turn, can contribute to solvate/stabilize the reactants, the reaction intermediates and the catalyst itself, thereby influencing its activity . DESs are known to be used not only as solvents, but also as ligands and active catalytic species in several metal‐catalyzed coupling reactions . Much work, however, still needs to be done to fully understand the basis of their effects in these processes .…”

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.…”

Ligand‐Free Suzuki–Miyaura Cross‐Coupling Reactions in Deep Eutectic Solvents: Synthesis of Benzodithiophene Derivatives and Study of their Optical and Electrochemical Performance

“…New emerging applications are related to organometallics, [25][26][27] metal-, [28][29][30][31][32][33][34] bio-, [35][36][37][38][39] and organocatalysis, [40][41][42] electrochemistry, [43] photosynthesis, [44] and solar technology. [45][46][47] Building upon our recent findings on metal-catalyzed crosscoupling reactions run in DESs in the absence of additional ligands, [30][31][32] herein we report a systematic study aimed at performing Suzuki-Miyaura (SM) coupling reactions between dibromo or diiodo BDT derivatives and (hetero)aryl-, alkenyl-and alkynyl boronic species in DESs, under ligandless and mild conditions. The newly 2,7-disubstituted BDT derivatives obtained in this study have been fully characterized, and their optical and electronic features thoroughly studied by means of UV/Vis absorption and cyclic voltammetry measurements.…”