Bifunctional Molecular Photoswitches Based on Overcrowded Alkenes for Dynamic Control of Catalytic Activity in Michael Addition Reactions

Stefano F. Pizzolato, Beatrice S. L. Collins, Thomas van Leeuwen, Ben L. Feringa*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

15 Citations (Scopus)

Abstract

The emerging field of artificial photoswitchable catalysis has recently shown striking examples of functional light-responsive systems allowing for dynamic control of activity and selectivity in organocatalysis and metal-catalysed transformations. While our group has already disclosed systems featuring first generation molecular motors as the switchable central core, a design based on second generation molecular motors is lacking. Here, the syntheses of two bifunctionalised molecular switches based on a photoresponsive tetrasubstituted alkene core are reported. They feature a thiourea substituent as hydrogen-donor moiety in the upper half and a basic dimethylamine group in the lower half. This combination of functional groups offers the possibility for application of these molecules in photoswitchable catalytic processes. The light-responsive central cores were synthesized by a Barton-Kellogg coupling of the prefunctionalized upper and lower halves. Derivatization using Buchwald-Hartwig amination and subsequent introduction of the thiourea substituent afforded the target compounds. Control of catalytic activity in the Michael addition reaction between (E)-3-bromo--nitrostyrene and 2,4-pentanedione is achieved upon irradiation of stable-(E) and stable-(Z) isomers of the bifunctional catalyst 1. Both isomers display a decrease in catalytic activity upon irradiation to the metastable state, providing systems with the potential to be applied as ON/OFF catalytic photoswitches.

Original languageEnglish
Pages (from-to)6174-6184
Number of pages11
JournalChemistry
Volume23
Issue number25
DOIs
Publication statusPublished - 2-May-2017
Event8th Munster Symposium on Cooperative Effects in Chemistry - Munster, Germany
Duration: 12-May-2017 → …

Keywords

  • activity control
  • Michael addition
  • molecular switches
  • photochemistry
  • photoswitchable catalysts
  • BAYLIS-HILLMAN REACTION
  • ASYMMETRIC CATALYSIS
  • SWITCHABLE ORGANOCATALYST
  • CHEMICAL-REACTIONS
  • BETA-CYCLODEXTRIN
  • AMINE-THIOUREAS
  • BOND DONORS
  • LIGHT
  • MOTORS
  • ROTAXANE

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