Asymmetric synthesis with cinchona-decorated cyclodextrin in a continuous-flow membrane reactor

Research output: Contribution to journalArticlepeer-review

  • External authors:
  • Peter Kisszekelyi
  • Abdulaziz Alammar
  • Jozsef Kupai
  • Peter Huszthy
  • Julia Barabas
  • Tibor Holtzl
  • Lajos Szente
  • Carlo Bawn
  • Gyorgy Szekely

Abstract

This work presents a cyclodextrin-enhanced organocatalytic method from molecular to process design. Cinchona-thiourea and -squaramide catalysts were covalently anchored to inherently large, stable and well-defined permethyl-β-cyclodextrins. The asymmetric catalysis was successfully demonstrated on the Michael reaction of 1,3-diketones and trans-β-nitrostyrene. Both emerging green and conventional solvents were screened for the asymmetric addition (up to 99% ee), and the Kamlet–Taft solvent parameters were correlated to the enantioselectivity. Quantum chemical modelling revealed that the catalyst anchoring resulted in favorable structural changes, and stronger intermolecular interactions between the catalyst and the reagents. Continuous organocatalysis was performed in coiled tube flow reactor coupled with a membrane separation unit, which allowed complete recovery of the catalyst and 50% solvent (2-MeTHF) recycling. The 100% conversion, 98% purity, 99% ee, 100% in-line catalyst recovery, and 80 g L−1 h−1 productivity makes it an attractive catalytic platform.

Bibliographical metadata

Original languageEnglish
Pages (from-to)255-261
JournalJournal of Catalysis
Volume371
Early online date15 Feb 2019
DOIs
Publication statusPublished - Mar 2019