Solvent-free catalytic isomerization of perfluoroalkyl allyl ethers

Abstract

A convenient method for the bulk preparation of environmentally safe perfluoroalkyl propen-1-yl ethers via isomerization of primary allyl ethers is presented. Herein the solvent-free isomerization was carried out in the presence of two ruthenium(II) complexes: the ruthenium-hydride [RuClH(CO)(PPh₃)₃] and the second generation Grubb's type catalyst dichloro[1,3-bis-(2,4,6-trimethylphenyl)-4,5-dimethylimidazol-2-ylidene](thien-2-ylmethylidene)(PCy₃) ruthenium(II) known as CatMETium_RF3™. A variety of reaction parameters such as the catalyst loading, the use of a base and UV photoirradiation have been investigated. We found that the presence of Bu₃N is beneficial to both catalytic systems and although CatMETium_RF3™ was shown to be more active than [RuClH(CO)(PPh₃)₃], the catalytic activity of the latter can also be sensibly improved by UV irradiation. Carrying out the isomerization reaction with 0.1 mol% of [RuClH(CO)(PPh₃)₃] under UV-irradiation led to a ca. 30% improvement of the conversion compared to the same reaction carried out under sunlight and to a 60% improvement when the reaction is carried out in the dark thus mimicking the conditions present in an autoclave.