Olefin Metathesis in Confinement: Towards Covalent Organic Framework Scaffolds for Increased Macrocyclization Selectivity. Issue 8 (5th January 2022)

• Record Type: Journal Article
• Authors: Emmerling, Sebastian T.; Ziegler, Felix; Fischer, Felix R.; Schoch, Roland; Bauer, Matthias; Plietker, Bernd; Buchmeiser, Michael R.; Lotsch, Bettina V.
• Is Part Of: Chemistry. Volume 28:Issue 8(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-01-05
• Subjects: catalysis -- confinement -- covalent organic frameworks -- metathesis -- reticular chemistry; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202104108
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Covalent organic frameworks (COFs) offer vast structural and chemical diversity enabling a wide and growing range of applications. While COFs are well‐established as heterogeneous catalysts, so far, their high and ordered porosity has scarcely been utilized to its full potential when it comes to spatially confined reactions in COF pores to alter the outcome of reactions. Here, we present a highly porous and crystalline, large‐pore COF as catalytic support in α, ω‐diene ring‐closing metathesis reactions, leading to increased macrocyclization selectivity. COF pore‐wall modification by immobilization of a Grubbs‐Hoveyda‐type catalyst via a mild silylation reaction provides a molecularly precise heterogeneous olefin metathesis catalyst. An increased macro(mono)cyclization (MMC) selectivity over oligomerization (O) for the heterogeneous COF‐catalyst (MMC:O=1.35) of up to 51 % compared to the homogeneous catalyst (MMC:O=0.90) was observed along with a substrate‐size dependency in selectivity, pointing to diffusion limitations induced by the pore confinement. Abstract : A biomimetic confinement and precise spatial arrangement of catalysts in porous media can provide increased selectivity for reactions compared to homogeneous catalysis. Herein, a covalent organic framework for molecular heterogeneous olefin metathesis is presented that utilizes spatial confinement of substrates in its pores for a substrate‐size dependent and increased macro(mono)cyclization selectivity.