Dialkylzinc mediated radical additions to chiral N-enoyloxazolidinones in the presence of benzaldehyde. Mechanistic investigation, structural characterization of the resulting γ-lactones

Diethylzinc was used in the presence of oxygen to mediate radical additions to chiral N-enoyloxazolidinones derived from fumaric acid. The synthesis of sterically crowded trisubstituted γ-lactones was achieved through a multicomponent reaction involving t-butyl iodide and benzaldehyde in addition to the above mentioned reagents. The domino process includes successively: iodine atom transfer, radical addition, homolytic substitution at zinc, aldol condensation, and lactonization. The diastereoselectivity of the reaction and the structural features of the resulting lactones were investigated. A tentative rationalization is discussed. Comparative experiments carried out with diisopropylzinc were performed.