[13283-01-7] · Cl6W · Tungsten(VI) Chloride · (MW 396.61)
Physical Data: dark blue crystals; mp 275 °C; bp 347 °C.
Solubility: sol ethanol, ether, benzene, carbon tetrachloride.
Form Supplied in: sold as a solid of high purity, often packaged in ampules.
Purification: used without further purification.
Handling, Storage, and Precautions: corrosive and moisture sensitive; stored in ampules.
Diazo compounds are converted to the corresponding carbenoid species by treatment with tungsten hexachloride.2 Tungsten hexachloride is superior to copper catalysts and common Lewis acids in effecting the [3 + 2] cycloaddition reaction between a-carbonyl carbenes and nitriles, forming isoxazoles (eq 1).
Treatment of b-hydroxy carboxylic acids with tungsten(VI) chloride and base leads to the b-lactones, which afford alkenes after thermal carbon dioxide expulsion (eq 2).3 The reaction occurs in one pot and is highly stereospecific. More examples have been examined using tungsten oxychloride.
James W. Herndon
University of Maryland, College Park, MD, USA