Synthesis of Ether‐Diols with Low Polarity from Long‐Chained Fatty Alcohols for Use in Block Copolymers
2019
Huber, Veronika Ramona | Riepl, Herbert Mathias
Diol‐terminated polyethers are important intermediates for the manufacturing of block copolymers, but only a few polyethers other than polyethylene glycols are available on a technical scale. Most of them are highly polar. Natural fatty alcohols—converted to similar polyethers—should have a grossly reduced polarity because of a large separation of the oxygen atoms in the C18 chain. A synthesis sequence of polyethers with a longer carbon chain compared to the ethylene glycol‐derived ethers based on commercially available fatty alcohols was designed for a future examination of the hydrophobic properties. Palladium‐catalyzed cleavage of olefinic dialkyl carbonates results in carbon dioxide elimination and subsequent formation of ethers from an allyl‐palladium cation. It could be shown that this process with fatty alcohols like undec‐10‐en‐1‐ol or oleyl alcohol can be run with appreciable yield. Although carbonates were obtained here using expensive chloroformates as starting materials, transesterification of dimethylcarbonates can be used similarly. Ruthenium‐catalyzed acyclic diene metathesis (ADMET) at both chain terminations then was applied to polymerize the ethers. Depending on the alkenyl chain, short oligomers with a degree of polymerization (DP) of about 5–8 seem to be formed according to gel permeation chromatography (GPC).
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