Highly efficient and chemoselective direct aldol reaction of acyldiazomethane with aldehydes promoted by MgI2 etherate

Direct aldol condensation of various aromatic, heteroaromatic, α,β-unsaturated aldehydes and aliphatic aldehydes with acyldiazomethane was realized using MgI₂ etherate (MgI₂·(Et₂O)_n) as a promoter in the presence of diisopropyl amine (DIPEA) in excellent yields in a short time under mild conditions with high chemoselectivity. Iodide counterion, and a non-coordinating less ploar reaction media (i.e., CH₂Cl₂) are among the critical factors for this unique reactivity.