Tungsten(VI) Chloride-n-Butyllithium


[13283-01-7]  · Cl6W  · Tungsten(VI) Chloride-n-Butyllithium  · (MW 396.61) (n-BuLi)

[109-72-8]  · C4H9Li  · Tungsten(VI) Chloride-n-Butyllithium  · (MW 64.07)

(deoxygenation of epoxides and carbonyl compounds1)

Physical Data: WCl6: dark blue crystals; mp 275 °C; bp 347 °C.

Solubility: WCl6: sol ethanol, ether, benzene, carbon tetrachloride. n-BuLi: sol hydrocarbon and ether solvents.

Form Supplied in: reaction of Tungsten(VI) Chloride and n-Butyllithium produces a poorly characterized species, thought to be a reduced form of tungsten. The compound obtained by mixing these two reagents is typically used without additional purification. Tungsten(VI) chloride is sold as a solid of high purity, often packaged in ampules. Butyllithium is sold as a solution in hexane, cyclohexane, or pentane.

Purification: both reagents are used without further purification.

Handling, Storage, and Precautions: WCl6: corrosive and moisture sensitive; stored in ampules. n-BuLi: reacts fairly violently with water and air; can be stored indefinitely provided the container is protected from the atmosphere.

Deoxygenation of Epoxides.

The combination of tungsten(VI) chloride and butyllithium leads to a structurally uncharacterized reagent which is very efficient for the deoxygenation of epoxides, affording alkenes.1 The reagent is stereospecific for the reduction of cyclic epoxides,1,2 but less stereoselectivity is observed during the preparation of acyclic alkenes from the corresponding epoxides. Reduction of monosubstituted epoxides often leads to substantial amounts of chlorohydrins, which are nonstereospecifically reduced by the reagent at higher temperatures. Tungsten(VI) chloride-butyllithium is the reagent of choice for deoxygenation of highly hindered epoxides. This reagent is effective for reduction of the epoxide functionality in the complex trichothecene derivative in eq 1,3 and the ryanodol synthesis intermediate in eq 2.4

Deoxygenative Dimerization of Carbonyl Compounds.

Treatment of carbonyl compounds with tungsten(VI) chloride-butyllithium leads to the corresponding symmetrical alkenes resulting from deoxygenation and coupling of the carbonyl compounds.1 The reaction proceeds most efficiently with aromatic aldehydes (eq 3) and less efficiently with aromatic ketones and aliphatic carbonyl compounds. The scope and limitations of this deoxygenative dimerization reaction have not been as thoroughly investigated as those employing low-valent titanium species.5

1. Sharpless, K. B.; Umbreit, M. A.; Nieh, M. T.; Flood, T. C. JACS 1972, 94, 6538; Umbreit, M. A.; Sharpless, K. B. OSC 1990, 7, 121.
2. Sattar, A.; Forrester, J.; Moir, M.; Roberts, J. S.; Parker, W. TL 1976, 17, 1403.
3. Roush, W. R.; Russo-Rodriguez, S. JOC 1987, 52, 598.
4. Bélanger, A.; Berney, D. J. F.; Borschberg, H.-J.; Brousseau, R.; Dotheau, A.; Durand, J.-P.; Katayama, H.; LaPalme, R.; Leturc, D. M.; Liao, C.-C.; MacLachlan, F. N.; Maffrand, J.-P.; Marazza, F.; Martino, R.; Moreau, C.; Saint Lauren, L.; Saintonge, R.; Soucy, P.; Ruest, L.; Deslongchamps, P. CJC 1979, 57, 3348.
5. McMurry, J. E. ACR 1983, 16, 405.

James W. Herndon

University of Maryland, College Park, MD, USA

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