Ring-Opening Metathesis Polymerization of Unsaturated Carbohydrate Derivatives: Levoglucosenyl Alkyl Ethers

Abstract

A series of biomass-derived levoglucosenyl alkyl ethers (alkyl = methyl, ethyl, n-propyl, isopropyl, and n-butyl) were synthesized and polymerized by ring-opening olefin metathesis polymerization using the Grubbs catalyst C793 at room temperature. Polymerizations were successfully performed in conventional solvents such as 1,4-dioxane and dichloromethane as well as in polar aprotic “green” solvents such as 2-methyltetrahydrofuran, dihydrolevoglucosenone (Cyrene), and ethyl acetate. The prepared polyacetals with degrees of polymerization of ∼100 exhibit Schulz–Flory-type molar mass distributions and are thermoplastic materials with rather low glass transition temperatures in the range of 43–0 °C depending on the length of the alkyl substituent. Kinetic studies revealed that the polymerization proceeded rapidly to a steady state with a certain minimum monomer concentration threshold. When the steady state was reached, just about half of the [Ru] catalyst had been effective to initiate the polymerization, indicating that the initiation step was a slow process. The remaining catalyst was still active and did no longer react with monomers but with in-chain double bonds, cutting the formed polymer chains into shorter fragments. In the long term, all catalyst was consumed and propagating [Ru] chain ends were deactivated by the elimination of [Ru] from the chain ends to form inactive chains with terminal aldehyde groups.

Toward E-selective Olefin Metathesis: Computational Design and Experimental Realization of Ruthenium Thio-Indolate Catalysts

“…Olefin metathesis offers an atomefficient catalytic alternative, in which olefinic fragments are rearranged by scission and regeneration of carbon-carbon double bonds [8][9][10]. Thanks to the ease of handling and functional-group tolerance of ruthenium catalysts [11][12][13], olefin metathesis has been widely adopted for the synthesis of complex organic molecules [14][15][16][17], including pharmaceuticals [18][19][20][21], and soft materials [22][23][24][25][26][27][28][29][30][31].…”

Cyrene: a bio-based novel and sustainable solvent for organic synthesis

“…In 2021, the polymerization of levoglucosenyl alkyl ethers 75 was investigated using various green solvents, including Cyrene. 44 The specific polymerization was mostly succeeded by employing a Grubb's catalyst ( C793 ) (Scheme 19). In that work, C793 was used as well and the ROM polymerization of the levoglucosenyl alkyl ethers afforded amorphous polyacetals with thermoplastic behavior, which were easily degradable by hydrolysis.…”

Trendbericht Makromolekulare Chemie 2022

“…Auch bei ringöffnenden Metathese-Polymerisationen lassen sich biobasierte Monomere und Lösemittel nutzen, was besonders schön die Polymerisation von Levoglucosenonderivaten in Dihydrolevoglucosenon zeigt: 12) Beide werden aus Cellulose gewonnen.…”