Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

Susanne Maria Fischer, Simon Renner, Adrian Daniel Boese, Christian Slugovc*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Electron-rich triarylphosphines, namely 4-(methoxyphenyl)diphenylphosphine (MMTPP) and tris(4-trimethoxyphenyl)phosphine (TMTPP), outperform commonly used triphenylphosphine (TPP) in catalyzing oxa-Michael additions. A matrix consisting of three differently strong Michael acceptors and four alcohols of varying acidity was used to assess the activity of the three catalysts. All test reactions were performed with 1 mol % catalyst loading, under solvent-free conditions and at room temperature. The results reveal a decisive superiority of TMTPP for converting poor and intermediate Michael acceptors such as acrylamide and acrylonitrile and for converting less acidic alcohols like isopropanol. With stronger Michael acceptors and more acidic alcohols, the impact of the more electron-rich catalysts is less pronounced. The experimental activity trend was rationalized by calculating the Michael acceptor affinities of all phosphine–Michael acceptor combinations. Besides this parameter, the acidity of the alcohol has a strong impact on the reaction speed. The oxidation stability of the phosphines was also evaluated and the most electron-rich TMTPP was found to be only slightly more sensitive to oxidation than TPP. Finally, the catalysts were employed in the oxa-Michael polymerization of 2-hydroxyethyl acrylate. With TMTPP polymers characterized by number average molar masses of about 1200 g/mol at room temperature are accessible. Polymerizations carried out at 80 °C resulted in macromolecules containing a considerable share of Rauhut–Currier-type repeat units and consequently lower molar masses were obtained.
Original languageEnglish
Pages (from-to)1689-1697
Number of pages9
JournalBeilstein Journal of Organic Chemistry
Publication statusPublished - 21 Jul 2021


  • Michael acceptor affinity
  • Michael addition chemistry
  • Organocatalysis
  • Phosphine
  • Solvent-free synthesis

ASJC Scopus subject areas

  • Organic Chemistry

Fields of Expertise

  • Advanced Materials Science


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