Isomerization of Allyl Ethers of Diols and Triols Catalyzed by Ruthenium Complexes

The allyl and propenyl ethers of diols and polyols have recently attracted increasing attention as monomers and comonomers [1–2]. Most convenient method of the preparation of propenyl ethers consists in isomerization of the corresponding, readily available allyl ethers. Moreover, this isomerization is a key step of deprotection of hydroxyl group, protected as allyl ether [3,4]. Particularly convenient catalysts of the isomerization of allyl to propenyl ethers are transition metal complexes. Complexes of ruthenium [5–8], rhodium [3,4], iridium [9], palladium [10], chromium [11], molybdenum [12], iron [13], platinum [14] and cobalt [15] were applied. In this communication, we describe the synthesis of propenyl ethers via isomerization of the corresponding allyl ethers of diols and triols catalyzed by [RuClH(CO)(PPh3)3] (Table). Other investigated ruthenium and rhodium complexes ([RuCl2(PPh3)3], [RuH2(PPh3)4], [Ru(CO)3(PPh3)2], [RhH(CO)(PPh3)3], [RuCl3 3H2O], [RhCl3 3H2O]) were less effective or even completely inactive. Quantitative yields of propenyl ethers were obtained only if a substrate contained neither triple bond nor allyl-hydroxyl group. Allyl ethers of 2-butyne-1,4-diol did not undergo isomerization to the corresponding propenyl ethers. It is likely that in this case stable acetylene complexes are formed: