A Mild C−O Bond Formation Catalyzed by a Rhenium-Oxo Complex

A mild method for the regioselective synthesis of propargyl ethers by the coupling of propargyl alcohols with a range of other alcohols is described. The method employs an air- and moisture-tolerant rhenium-oxo complex ((dppm)ReOCl3) as a catalyst for the formation of sp3-carbon-oxygen bonds without the need for prior activation of the propargyl alcohol or deprotonation of the alcohol nucleophile. A broad range of functional groups is tolerated, including aryl halides, olefins, esters, and acid-labile functional groups such as acetals. Furthermore, displacement of the alcohol occurs preferentially even in the presence of other electrophiles such as primary alkyl halides and conjugated esters.