Organocatalytic Asymmetric Conjugate Addition of Aldehydes to Maleimides and Nitroalkenes in Deep Eutectic Solvents

Abstract

A chiral primary amine-salicylamide is used as an organocatalyst for the enantioselective conjugate addition of α,α-disubstituted aldehydes to maleimides and nitroalkenes. The reactions are performed in deep eutectic solvents as reaction media at room temperature, leading to the corresponding adducts with enantioselectivities up to 88% (for maleimides) and 80% (for nitroalkenes). Catalyst and solvent can be recovered and reused.

Asymmetric Organocatalysis in Deep Eutectic Solvents

“…This enantioselective Michael addition reaction between α,α‐disubstituted aldehydes and N‐substituted maleimides have also been carried out in DESs at room temperature using a monosalicylamide derived from (1 R ,2 R )‐cyclohexane‐1,2‐diamine as an organocatalyst (10 mol%) (Scheme 5). [18] In this case, the chosen DES was formed by the combination of ChCl/ethylene glycol (1/2 molar ratio), and the presence of 10 mol% of 4‐nitrobenzoic acid improved both yield and enantioselectivity. The obtained enantioselections for the final adducts were generally slightly lower than when using the former organocatalyst in the same process.…”

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

“…Because of a low ecological footprint and unusual physicochemical properties, DESs are progressively replacing toxic, petroleum-derived VOCs in several fields of science. 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.…”

“…Because of a low ecological footprint and unusual physicochemical properties, DESs are progressively replacing toxic, petroleum‐derived VOCs in several fields of science. New emerging applications are related to organometallics, [ 25–27 ] metal‐, [ 28–34 ] bio‐, [ 35–39 ] and organocatalysis, [ 40–42 ] electrochemistry, [ 43 ] photosynthesis, [ 44 ] and solar technology. [ 45–47 ]…”