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Olefin Ring‐closing Metathesis under Spatial Confinement and Continuous Flow
Author(s) -
Ziegler Felix,
Roider Thomas,
Pyschik Markus,
Haas Christian P.,
Wang Dongren,
Tallarek Ulrich,
Buchmeiser Michael R.
Publication year - 2021
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.202001993
Subject(s) - trimer , selectivity , metathesis , random hexamer , chemistry , monomer , salt metathesis reaction , ring opening metathesis polymerisation , dimer , catalysis , chemical engineering , polymerization , organic chemistry , polymer , crystallography , engineering
We report on the use of a 2 nd ‐generation Hoveyda–Grubbs‐type catalyst immobilized inside mesoporous silica for the application in selective macro(mono)cyclization (MMC) of an α,ω‐diene under spatially confined and continuous‐flow conditions. Reactions carried out with different flow rates allow for variations in residence time; conversion and MMC selectivity can be determined for well‐defined reaction times. Analysis of the reaction mixtures obtained for different reaction times and temperatures in a single flow experiment by NMR and MALDI‐TOF‐MS allows to address confinement effects and to determine olefin metathesis pathways. These investigations revealed that ring‐chain equilibria are quickly established but substantially affected by residence time and flow, allowing for the determination of conditions under which MMC selectivity reaches a maximum. In contrast to reactions carried out in solution, in which oligomers up to the hexamer were observed, MMC under confinement predominantly proceeds via ring‐closing metathesis of the monomer and backbiting from the dimer and trimer, but not from higher oligomers as their formation is suppressed. This leads to the observed high MMC selectivity, reaching 60 % at a 25 mM substrate concentration.