doi:10.3390/catal8080305engGiménez Sonsona, I.Marqués-López, E.Häring, M.Díaz, D.Pérez Herrera, R.Urea activation by an external brønsted acid: Breaking self-association and tuning catalytic performanceART-2018-107612In 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.2018http://zaguan.unizar.es/record/7496710.3390/catal8080305http://zaguan.unizar.es/record/74967oai:zaguan.unizar.es:74967info:eu-repo/grantAgreement/ES/DGA/E07-17Rinfo:eu-repo/grantAgreement/ES/MINECO/CTQ2017-88091-Pinfo:eu-repo/grantAgreement/ES/UZ/JIUZ-2017-CIE-05CATALYSTS 8, 8 (2018), 305 [21 pp]byhttp://creativecommons.org/licenses/by/3.0/es/info:eu-repo/semantics/openAccess