Asymmetric Synthesis at Prochiral Centers: Substituted 1,3-Dioxolanes

Article abstract of DOI:10.1021/jo00338a011

Asymmetric substitution at the prochiral carbon atom of two series of 2-substituted 4,5-dimethyl-1,3-dioxolanes is studied; the hydroxy ethers formed by reaction with the "mixed hydride reagent" LiAlH4/AlCl3 show a marked influence of the substitutents on the asymmetric induction, i.e., from 4percent to 98percent diastereomeric excess (de).The dioxolanes are studied by both 13C NMR and 1H NMR spectroscopy and their chemical shift inequivalences correlate well with the de, provided that no unsaturated residues are present.The proposed mechanism is based on preferred complexation of the hydride reagent with one of the diastereotopic oxygen atoms.This is supported by a drastic decrease of the de if further ether groups are introduced into the substrate molecules.