Studies on the Regioselectivity of Horner-Wadsworth-Emmons (Hwe) Reactions on 3,4-Enuloses. Further Evidence of Phosphonate-Phosphate Rearrangements Through Five Membered Cyclic Intermediates.

OSCAR M. MORADEI; CECILE M. DU MORTIER; ALICIA FERNÁNDEZ CIRELLI

JOURNAL OF CARBOHYDRATE CHEMISTRY

Taylor & Francis

Año: 1999 vol. 18 p. 709 - 719

0732-8303

The Horner-Wadsworth-Emmons (HWE) reaction was performed on methyl 3,6-di-O-benzoyl-2-deoxy- -D-glycero-hex-2-enopyranosid-4-ulose (1) with the potassium enolates of dimethyl [(methoxycarbonyl)methyl]phosphonate (2) or diethyl [(ethoxycarbonyl) methyl]phosphonate (3) under different conditions (metallic cation and solvent) in order to study regio- and stereochemical aspects of the reaction. In the presence of lithium ions, no reaction took place. When sodium enolates were employed, 1,2-addition was the main reaction in chelating solvents, whereas the 1,4-adduct is favoured in the less polar, non chelating toluene. Only 1,2-addition was observed with potassium enolates. Evidence of phosphonate-phosphate rearrangements through five membered cyclic intermediates is described.