Synthesis of Ether-Diols with Low Polarity from Long-Chained Fatty Alcohols for Use in Block Copolymers

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).