[16800-47-8]  · C9H9N3O3W  · Tris(acetonitrile)tricarbonyltungsten  · (MW 391.06)

(catalyst for nucleophilic substitution of allylic acetates1)

Physical Data: mp 135 °C (dec).

Solubility: sol acetonitrile, nitromethane.

Form Supplied in: not commercially available.

Preparative Methods: by refluxing Hexacarbonyltungsten in Acetonitrile in an inert atmosphere. Removal of solvent under an inert atmosphere yields tris(acetonitrile)tricarbonyltungsten.2 Solutions of the reagent can be prepared by photolysis of hexacarbonyltungsten in acetonitrile.

Purification: can be purified by recrystallization from acetone-hexane.3 The crude solid or solution obtained in the above preparations is typically used without further purification.

Handling, Storage, and Precautions: air and thermally sensitive; pyrophoric. Use in a fume hood.

Allylic Alkylation.

Treatment of allylic acetates or carbonates with various carbon nucleophiles in the presence of tris(acetonitrile)tricarbonyltungsten and bipyridyl leads to the allylic alkylation product (eqs 1 and 2).1 Suitable nucleophiles include those derived from carbon acids having a pKa < ~18. The reaction proceeds with retention of configuration (eq 1) and preferentially produces the allylic regioisomer, where nucleophilic attack occurs at the carbon best able to stabilize a positive charge. This is in contrast to palladium-catalyzed allylic alkylation, where the nucleophilic attack generally occurs preferentially at the less-substituted carbon of the allylic system.4

Related Reagents.

Palladium(II) Acetate; Palladium(II) Chloride; Tetrakis(triphenylphosphine)palladium(0).

1. Trost, B. M.; Hung, M. H. JACS 1983, 105, 7757.
2. Faller, J. W.; Haitko, D. A.; Adams, R. D.; Chodosh, D. F. JACS 1979, 101, 865.
3. Tate, D. P.; Knipple, W. R.; Augl, J. M. IC 1962, 1, 433.
4. Trost, B. M. ACR 1980, 13, 385.

James W. Herndon

University of Maryland, College Park, MD, USA

Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.