Metallaphotoredox Catalysis Unlocks Aldehydes as Safe and Versatile Nonstabilized Carbene Precursors

The direct generation of nonstabilized carbenes from simple feedstocks represents a central challenge in modern organic synthesis. Traditional reliance on diazo compounds imposes significant limitations in safety and functional group compatibility. Herein, we describe a transformative strategy that merges photoredox and iron catalysis, utilizing a transient ligated boryl radical to directly unlock abundant aliphatic aldehydes as practical and powerful carbene precursors. This paradigm shift enables a diverse array of cyclopropanation and X–H insertion reactions under simple, mild, and safe conditions, heralding a new era for carbene chemistry using foundational chemical feedstocks.