Chemoselective reduction of α-keto aldehydes by rongalite in water: a metal- and hydride-free approach.

A chemoselective reduction of α-keto aldehydes using rongalite in water has been developed for the efficient synthesis of α-hydroxymethyl ketones. This transformation exploits the unique reactivity of rongalite to achieve a mild, metal- and hydride-free reduction that proceeds smoothly in the presence of various functional groups. The protocol employs inexpensive rongalite (ca. $0.03 per gram), operates in an aqueous medium under open-air conditions, and requires no inert atmosphere. The reaction is readily scalable to gram quantities and exhibits excellent chemoselectivity and broad substrate scope, tolerating electron-donating, electron-withdrawing, and halogen substituents, as well as hetero aromatics, delivering the desired products in high yields within short reaction times.