Iridium-Catalyzed Asymmetric Transfer Hydrogenation of Alkynyl Ketones Using Sodium Formate and Ethanol as Hydrogen Sources

A green and efficient iridium-catalyzed asymmetric transfer hydrogenation of alkynyl ketones to chiral propargylic alcohols has been developed. By using sodium formate and ethanol as hydrogen sources, a series of alkynyl ketones were hydrogenated by chiral spiro iridium catalyst (S)-1b to provide optically active chiral propargylic alcohols with up to 98% ee under base-free conditions. This protocol provides a practical and sustainable method for the preparation of optically active propargylic alcohols.