Etherification reactions of propargylic alcohols catalyzed by a cationic ruthenium allenylidene complex

The cationic ruthenium allenylidene complex RRuRax - [Ru(indenyl)L(PPh3)=C=C=CPh2]+PF6 catalyzes the etherification of secondary and tertiary propargylic alcohols in a formal nucleophilic substitution reaction utilizing primary and secondary alcohols as the nucleophiles. At a catalyst loading of only 1.1 mol%, the corresponding propargylic ether products were obtained in 9 to 73% isolated yields (18 h reaction time at 100 degrees C); no further additives are required. The reaction exhibits an induction period; as shown by a control reaction, the high reaction temperature may chemically change the allenylidene complex to be employed as the catalyst but does not lead to catalyst deactivation. (C) 2014 Elsevier B.V. All rights reserved.