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Open AccessArticle

Urea Activation by an External Brønsted Acid: Breaking Self-Association and Tuning Catalytic Performance

Laboratorio de Organocatálisis Asimétrica, Departamento de Química Orgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH) CSIC-Universidad de Zaragoza, C/ Pedro Cerbuna 12, 50009 Zaragoza, Spain
Institut für Organische Chemie, Universität Regensburg Universitätsstr. 31, 93053 Regensburg, Germany
Institute of Advanced Chemistry of Catalonia-Spanish National Research Council (IQAC-CSIC), Jordi Girona 18-26, 08034 Barcelona, Spain
Authors to whom correspondence should be addressed.
Catalysts 2018, 8(8), 305;
Received: 8 July 2018 / Revised: 24 July 2018 / Accepted: 25 July 2018 / Published: 28 July 2018
(This article belongs to the Special Issue Hydrogen Bonding Activation)
PDF [10682 KB, uploaded 28 July 2018]


In this work, we hypothesize that Brønsted acids can activate urea-based catalysts by diminishing its self-assembly tendency. As a proof of concept, we used the asymmetric Friedel–Crafts alkylation of indoles with nitroalkenes as a benchmark reaction. The resulting 3-substituted indole derivatives were obtained with better results due to cooperative effects of the chiral urea and a Brønsted acid additive. Such synergy has been rationalized in terms of disassembly of the supramolecular catalyst aggregates, affording a more acidic and rigid catalytic complex. View Full-Text
Keywords: Brønsted acids; Friedel-Crafts; organocatalysis; self-association; synergy; urea Brønsted acids; Friedel-Crafts; organocatalysis; self-association; synergy; urea

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Sonsona, I.G.; Marqués-López, E.; Häring, M.; Díaz, D.D.; Herrera, R.P. Urea Activation by an External Brønsted Acid: Breaking Self-Association and Tuning Catalytic Performance. Catalysts 2018, 8, 305.

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