Diboron‐Mediated Chemoselective Radical Reduction of 4‐Acylpyridines to Alcohols Under Metal‐Free Aqueous Conditions

Radical reduction of carbonyl compounds is a powerful transformation typically achieved using single‐electron transfer (SET) reagents such as samarium diiodide (SmI 2 ) or alkali metals. While effective, these methods often require strictly anhydrous conditions, inert atmospheres, or expensive reagents. Herein, we report a robust, transition metal‐free protocol for the radical‐type reduction of 4‐acylpyridines to secondary alcohols using diboron reagents in water. This system serves as an air‐stable surrogate for classical SET reductants. The diboron/water system operates under mild conditions, ensuring high chemoselectivity toward the exocyclic carbonyl group while preserving the heteroaromatic core. Preliminary mechanistic investigations support a radical pathway, highlighting the capability of diboron reagents to function as effective radical reductants in aqueous media.