Rh-Catalyzed Hydroformylation of Benzylidenecyclopropanes with Formic Acid

A Rh-catalyzed hydroformylation of benzylidenecyclopropanes with HCO2H/Ac2O is described. A wide variety of ring-opening linear γ,δ-unsaturated aldehydes or 2-cyclopropyl-2-arylacetaldehydes can be obtained in up to 82% or 70% yield, respectively, by a judicious choice of the reaction conditions. The reaction is operationally simple and avoids the use of gaseous CO and H2.