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Molecules 2018, 23(6), 1374; https://doi.org/10.3390/molecules23061374

Chiral 2-Aminobenzimidazole as Bifunctional Catalyst in the Asymmetric Electrophilic Amination of Unprotected 3-Substituted Oxindoles

Departamento de Química Orgánica and Instituto de Síntesis Orgánica (ISO), Facultad de Ciencias, Universidad de Alicante, Apdo. 99, E-03080 Alicante, Spain
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Received: 9 May 2018 / Revised: 4 June 2018 / Accepted: 5 June 2018 / Published: 6 June 2018
(This article belongs to the Special Issue Stereogenic Centers)
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Abstract

The use of readily available chiral trans-cyclohexanediamine-benzimidazole derivatives as bifunctional organocatalysts in the asymmetric electrophilic amination of unprotected 3-substituted oxindoles is presented. Different organocatalysts were evaluated; the most successful one contained a dimethylamino moiety (5). With this catalyst under optimized conditions, different oxindoles containing a wide variety of substituents at the 3-position were aminated in good yields and with good to excellent enantioselectivities using di-tert-butylazodicarboxylate as the aminating agent. The procedure proved to be also efficient for the amination of 3-substituted benzofuranones, although with moderate results. A bifunctional role of the catalyst, acting as Brønsted base and hydrogen bond donor, is proposed according to the experimental results observed. View Full-Text
Keywords: organocatalysis; electrophilic amination; benzimidazoles; asymmetric catalysis; oxindoles organocatalysis; electrophilic amination; benzimidazoles; asymmetric catalysis; oxindoles
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Benavent, L.; Baeza, A.; Freckleton, M. Chiral 2-Aminobenzimidazole as Bifunctional Catalyst in the Asymmetric Electrophilic Amination of Unprotected 3-Substituted Oxindoles. Molecules 2018, 23, 1374.

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