Catalyst speciation and deactivation in the ruthenium-mediated transformation of ethynyl-β-ionol to α,β-unsaturated esters for vitamin A synthesis

Asad Saib, Roman Goy, Jonathan Medlock, Bettina Wüstenberg, Gabriele Kociok-Köhn, Catherine L. Lyall, John P. Lowe, Ulrich Hintermair

Research output: Contribution to journalArticlepeer-review

Abstract

The catalytic anti-Markovnikov addition of carboxylic acids to propargylic alcohols to furnish unsaturated esters is an appealing transformation due to its mild conditions, good selectivity and high atom economy. Treatment of the γ-hydroxy α,β-unsaturated esters with Brønsted acids gives access to enals which serve as important building blocks for the production of vitamins and aroma compounds from biogenic terpenes. Unfortunately, current turnover numbers (TON) for this ruthenium-catalysed reaction are too low for industrial application (<100). Here we present a detailed investigation into the speciation and deactivation of the most active [(dppe)RuII(MA)2] catalyst in the anti-Markovnikov addition of carboxylic acids to ethynyl-β-ionol. Multi-nuclear high resolution FlowNMR spectroscopy gave insight into a range of kinetically relevant carboxylate complexes, allowed quantifying catalyst deactivation kinetics, and showed a pronounced influence of the carboxylic acid on catalyst stability. Systematic optimisation of reaction parameters resulted in significant improvements in catalyst productivity to reach TONs of >450 for ethynyl-β-ionol and >2000 for phenylacetylene.

Original languageEnglish
Pages (from-to)355-375
Number of pages21
JournalCatalysis Science and Technology
Volume15
Issue number2
Early online date21 Nov 2024
DOIs
Publication statusPublished - 21 Jan 2025

Data Availability Statement

The datasets supporting this article have been uploaded as part of the ESI.† Crystallographic details can be retrieved from the Cambridge Crystallographic Data Centre under deposition numbers 2296242–2296250.

Acknowledgements

The authors would like to thank colleagues at DSM-Firmenich (Werner Bonrath, Claude Furer, Marcel Joray, Estel Canet-Martinez, Charalampos Panagos, Ralph Waechter and Helen Yeman) for their contributions to this project, as well as Andrew Weller (University of York) and Jordi Burés (University of Manchester) for helpful discussions.

Funding

This work was supported by the Royal Society (UF160458; fellowship to UH), the EPSRC (Dynamic Reaction Monitoring Facility at the University of Bath EP/P001475/1), and DSM-Firmenich (CASE studentship to A. S.).

FundersFunder number
The Royal SocietyUF160458
Engineering and Physical Sciences Research CouncilEP/P001475/1
dsm-firmenichCASE studentship

ASJC Scopus subject areas

  • Catalysis

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