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Chiral 2-Aminobenzimidazoles in Deep Eutectic Mixtures: Recyclable Organocatalysts for the Enantioselective Michael Addition of 1,3-Dicarbonyl Compounds to β-Nitroalkenes

2017; American Chemical Society; Volume: 5; Issue: 11 Linguagem: Inglês

10.1021/acssuschemeng.7b02613

2168-0485

Diego Ros Ñíguez, Gabriela Guillena, Diego A. Alonso,

Asymmetric Synthesis and Catalysis

A catalytic system based on deep eutectic solvents (DESs) and chiral 2-amino benzimidazole organocatalysts is used to promote the enantioselective addition of 1,3-dicarbonyl compounds to β-nitrostyrenes. This procedure avoids the use of toxic volitile organic compounds (VOCs) as a reaction medium, providing access to highly functionalized chiral molecules in a selective and efficient manner. Furthermore, the reaction can be performed on a large scale and recycling the catalytic system is possible for at least four times, leading to a clean, cheap, simple, and scalable procedure that meets most of the criteria required to be a green and sustainable process. Nuclear magnetic resonance studies have confirmed the key role of the hydrogen-bonding interactions between the DES and the chiral organocatalyst, which allow their recovery and the recyclability of the system.