Chiral Primary Amine-Catalyzed Divergent Coupling of α-Substituted Acrylaldehydes with α-Diazoesters

We report, herein, aminocatalytic coupling of alpha-substituted acrylaldehydes with alpha-diazoesters, leading to chemoselective C-H insertion or cyclopropanation depending on alpha-substituents of diazoesters. A chiral primary-secondary diamine catalyst derived from L-tert-leucine enabled the efficient promotion of both C-H insertion and cyclopropanation pathways in good yields and high enantioselectivities at room temperature without any metal or a Lewis acid cocatalyst. Mechanistic studies uncovered an iminium ion-mediated 1,3-dipolar cycloaddition pathway, wherein the electronic nature of diazocarbons dictates the chemoselectivity in this aminocatalytic cycle.