[16923-43-6] · Cl6K2W · Potassium Hexachlorotungstate(IV) · (MW 474.75)
(reduces 1,2-diols to alkenes1)
Physical Data: red crystals.
Solubility: sol liquid ammonia.
Form Supplied in: not commercially available.
Preparative Method: prepared by heating a mixture of Tungsten(VI) Chloride and Potassium Iodide at 130 °C in the absence of air.2
Purification: the compound from the above procedure is used without further purification.
Handling, Storage, and Precautions: air and moisture sensitive.
Treatment of potassium hexachlorotungstate(IV) with the dialkoxides derived from deprotonation of 1,2-diols leads to alkenes.1 The procedure represents a one-pot method to effect this transformation; sequential treatment of 1,2-diols with n-Butyllithium, followed by potassium hexachlorotungstate(IV), leads to the desired alkene in high yield. The reaction is fastest for tetrasubstituted diols and slows with decreasing substitution (eq 1). Predominant but not exclusive retention of stereochemistry is observed in the reaction, due to partial isomerization of the dialkoxides under the conditions of the reaction; the isomerization is thought to proceed via a reversible pinacol coupling. The advantages of this method are that it is a one-pot procedure, and that it is efficient for hindered substrates.3
James W. Herndon
University of Maryland, College Park, MD, USA