Conversion of α-Haloaldehydes into Acylating Agents by an Internal Redox Reaction Catalyzed by Nucleophilic Carbenes

Reactivity umpolung allows us to consider nontraditional bond disconnections. We report herein that treatment of an alpha-haloaldehyde with a nucleophile in the presence of catalytic amounts of nucleophilic carbenes results in an internal redox reaction giving rise to a dehalogenated acylating agent as an intermediate by a new reaction manifold. A brief illustration of the scope of this reaction is presented along with evidence supporting the direct intervention of the carbene in the acylation step.