Action des organomagnésiens sur les composés β-dicarbonylés V. Synthèses de β-diols bitertiaires à partir de β-hydroxycétones. Induction asymétrique 1-3

Abstract

Addition of organomagnesium compounds to β-hydroxyketones with an asymmetric center gave a diastereoisomeric mixture of symmetric ditertiary β-diols, the ratio of meso and threo forms depending on the nature of the inductive group.The configurations of the β-diols were determined using their respective n.m.r. spectra in which the methyl and the methylene protons have different chemical shifts.The conformations of the β-hydroxyketones and the β-diols were studied by i.r. spectroscopy. Models for a preferred attack of the organomagnesium compounds are proposed and product-determining transition states for the reactions are also suggested.