Membrane-Grafted Asymmetric Organocatalyst for an Integrated Synthesis-Separation Platform

Christos Didaskalou, Jozsef Kupai, Levente Cseri, Julia Barabas, Elemer Vass, Tibor Holtzl, Gyorgy Szekely*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

59 Scopus citations

Abstract

In this work we introduce a sustainable membrane-based synthesis-separation platform for enantioselective organocatalysis. An azido derivatized cinchona-squaramide bifunctional catalyst was synthesized and subsequently grafted to the surface of a polybenzimidazole-based nanofiltration membrane. The favorable effect of the covalent grafting - due to the change in geometry and increased secondary interactions - on the catalytic activity due to conformational changes was confirmed by quantum chemical calculations. Asymmetric Michael and aza-Michael reactions of 1,3-dicarbonyl and indole, pyrazole, and triazole derivatives to β-nitrostyrene were performed with as high as 99% enantiomeric excess. This report on the enantioselective aza-Michael reaction of pyrazoles and triazoles opens new frontiers in the application of squaramide-based cinchona catalysts. A catalytic membrane cascade reactor was developed for an integrated synthesis-purification process allowing at least 98% product and substrate recovery, and quantitative in situ solvent recycling. The sustainability of the synthetic methodology was assessed through E-factor and carbon footprint.

Original languageEnglish (US)
Pages (from-to)7430-7438
Number of pages9
JournalACS Catalysis
Volume8
Issue number8
DOIs
StatePublished - Aug 3 2018

Keywords

  • Michael addition
  • catalytic membrane reactor
  • cinchona-squaramide
  • enantioselective catalysis
  • organic solvent nanofiltration
  • polybenzimidazole
  • recycling
  • surface modification

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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