Lewis acid catalyzed dipolar cycloadditions of an activated imidate

An evaluation of simple Lewis acids revealed that N-malonylimidates undergo catalyzed [3+2] cycloaddition reactions with aldehydes, imines, and activated olefins to form oxazolines, imidazolines, and pyrrolines, respectively. Reactions proceed optimally at ambient temperature with the addition of 5 mol % Of MgCl2 in CH3CN. Experiments aimed at elucidation of the reactive intermediate undergoing cycloaddition suggest that the Lewis acid promotes a 1,2-prototropic shift to give a metal-coordinated azomethine ylide, rather than ionization and proton transfer to give a nitrile ylide.