1,3-DIPOLAR CYCLOADDITION OF IMIDATE YLIDES ON IMINO-ALCOHOLS - SYNTHESIS OF NEW IMIDAZOLONES USING SOLVENT-FREE CONDITIONS

Imidates derived from a-amino esters as potential azomethine ylides, undergo 1,3-dipolar cycloaddition with imino-alcohols, in tautomeric equilibrium with 1,3-oxazolidines, without solvent at 70 degrees C or under microwave irradiation. This reaction leads to a wide range of novel polyfunctionalized 4-yliden-2-imidazolin-5-ones in good yields with short reaction times. The reactivity of these imidates derived from alpha-amino esters with imino-alcohols is rationalized from the energy of the Frontier Molecular Orbitals (FMO) determined by semi-empirical PM3 calculations : the reaction is controlled by the interaction HOMO((1,3-dipole)) - LUMO((dipolarophile)) and the second order pertubation energy calculations are in agreement with the experimental reaction orientation.