2-IMINOOXETANE CHEMISTRY .3. SYNTHESIS OF BETA-HYDROXY AMIDES

Beta-Hydroxy amides were synthesized by hydrolysis of the corresponding 2-iminooxetanes, which were prepared in a very simple step by lanthanide-catalyzed cycloaddition of aldehydes to ketene imines. The stereochemical outcome of the hydrolysis, performed under neutral (DMSO/H2O) or acidic (H2SO4/H2O) conditions, depends on the steric and electronic nature of the substituents, which play a crucial role in the ring-opening mechanism. Experiments done with O-18-labeled water showed that two alternatives are possible: one involving ring opening of the oxetane at the C4-O bond, the other involving ring opening at the C2-O bond.