Continuous flow heterogeneous catalytic reductive aminations under aqueous micellar conditions enabled by an oscillatory plug flow reactor

• Michaela Wernik^a,b
• Gellért Sipos^c,d
• Balázs Buchholcz^e
• Ferenc Darvas^c,d
• Zoltán Novák^f
• Sándor B. Ötvös^a,b
• C. Oliver Kappe^a,b

• ^aInstitute of Chemistry, University of Graz, NAWI Graz, Heinrichstrasse 28, A-8010 Graz, Austria
• ^bCenter for Continuous Flow Synthesis and Processing (CCFLOW), Research Center Pharmaceutical Engineering GmbH (RCPE), Inffeldgasse 13, A-8010 Graz, Austria
• ^cThalesNano Inc., Záhony u. 7, 1031 Budapest, Hungary
• ^dComInnex Inc., Záhony u. 7, 1031 Budapest, Hungary
• ^eInnostudio Inc., Záhony u. 7, 1031 Budapest, Hungary
• ^fELTE “Lendület” Catalysis and Organic Synthesis Research Group, Faculty of Science, Institute of Chemistry, Eötvös Loránd University, Pázmány Péter stny. 1/a, 1117 Budapest, Hungary

Despite the fact that continuous flow processing exhibits well-established technical advances, aqueous micellar chemistry, a field that has proven extremely useful in shifting organic synthesis to sustainable water-based media, has mostly been explored under conventional batch-based conditions. This is particularly because of the fact that the reliable handling of slurries and suspensions in flow has been considered as a significant technical challenge. Herein, we demonstrate that the strategic application of an oscillatory plug flow reactor enables heterogeneous catalytic reductive aminations in aqueous micellar media enhancing mass transport and facilitating process simplicity, stability and scalability. The micellar flow process enabled a broad range of substrates, including amino acid derivatives, to be successfully transformed under reasonably mild conditions utilizing only very low amounts of Pd/C as a readily available heterogeneous catalyst. The preparative capabilities of the process along with the recyclability of the heterogenous catalyst and the aqueous reaction media were also demonstrated.

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