Ruthenium-Catalyzed Propargylic Reduction of Propargylic Alcohols with Hantzsch Ester

Ruthenium-catalyzed propargylic reduction of propargylic alcohols bearing a terminal alkyne moiety is accomplished by using Hantzsch ester as a nucleophilic hydride source. A variety of secondary and tertiary propargylic alcohols are reduced to the corresponding propargylic reduced products such as 1-alkynes in excellent yields. Some mechanistic studies indicate that ruthenium–allenylidene complexes may work as key reactive intermediates.