title: Effect of a Phosphazene Base on the Diastereoselectivity of Addition of alpha-Sulfonyl Carbanions to Butyraldehyde and Isopropylideneglyceraldehyde.
abstract: The effect of tBuP4, a strong and cation-free base, on the yield and diastereoselectivity of additions of thus formed "naked" alpha-sulfonyl carbanions to achiral butyraldehyde and chiral isopropylideneglyceraldehyde was studied. It has been found that with tBuP4 a reasonable yield ( approximately 55%) and a slightly better diastereoselectivity (72% of the anti diastreomer) are obtained with achiral and nonfunctionalized butyraldehyde while with isopropylideneglyceraldehyde the use of tBuP4 allowed us to greatly increase the yields (up to 95-100%) and the diastereoselectivities (83-89% of a single diastereomer over the four possible diastereomers). It was also shown that the extra oxygen atom in the alpha-position plays a determinant role in this effect.
authors.affiliation: Laboratoire de Cristallochimie, associé au CNRS, Université Louis Pasteur, 4 rue Blaise Pascal, 67070 Strasbourg, France.
authors.forename: Arlette
authors.initials: A
authors.lastname: Solladié-Cavallo
authors.forename: Didier
authors.initials: D
authors.lastname: Roche
authors.forename: Jean
authors.initials: J
authors.lastname: Fischer
authors.forename: André
authors.initials: A
authors.lastname: De Cian