Copper-catalyzed formylation of alkenyl C-H bonds using BrCHCl2 as a stoichiometric formylating reagent.

The first example of copper-catalyzed direct formylation of alkenyl C-H bonds for the facile synthesis of α,β-unsaturated aldehydes has been developed. This transformation has demonstrated high reactivity, mild reaction conditions and a broad substrate scope. BrCHCl2 is expected to be developed as an efficient stoichiometric C1 building block in organic synthesis.