Palladium(II) Trifluoroacetate


[42196-31-6]  · C4F6O4Pd  · Palladium(II) Trifluoroacetate  · (MW 332.46)

(palladium catalyst used in the oxidation of alkenes3-5 and C-C bond formation6-8)

Physical Data: mp 210 °C (dec).

Solubility: sol diethyl ether, acetone; insol benzene, chloroform, trifluoroacetic acid.

Form Supplied in: brown powder; commercially available.

Analysis of Reagent Purity: IR: n 1690, 1435 cm-1.

Preparative Methods: by reaction of Palladium(II) Acetate with excess Trifluoroacetic Acid on a steam bath, to yield a brown powder after drying in vacuo.1 The reagent is also prepared in 89% yield by reaction of Palladium(II) Chloride with aqueous hydrochloric acid, then 15% sodium hydroxide solution at 85 °C, followed by excess trifluoroacetic acid at 80 °C.2

Handling, Storage, and Precautions: stable solid; irritant and hygroscopic.

Oxidation of Alkenes.

Photolysis of oxygenated acetone solutions of allylsilanes with an arylsulfonyl group at the allylic position in the presence of the title reagent (1) affords a,b-enals and a,b-enones (eq 1).3 Palladium(II) trifluoroacetate also catalyzes the oxidation of styrene to acetophenone in the presence of an oxygen atom donor such as a molozonide (2) (eq 2).4

Allylic Acetoxylations.

The terminal allylic methyl group of geranylacetone is selectively oxidized with a catalytic amount of (1), 1,4-Benzoquinone as oxidant, o-methoxyacetophenone as added ligand, and acetic acid as solvent (eq 3).5

Alkylidenecyclopentenedione Synthesis.

The 4-alkynyl-4-hydroxycyclobutenone ring system rearranges with ring expansion to alkylidenecyclopentenediones in the presence of (1) (eq 4).6 A similar selective ring expansion has provided 2-alkylideneindene-1,3-dione monoacetals (eq 5).6 In both cases the nonvinylic C-C bond migrates more rapidly.

Tetraene Carbocyclizations.

Cyclization of a tetraene employing a catalytic amount of (1) with Triphenylphosphine as an additive in THF afforded a 73% yield of the cyclized and intramolecularly trapped diene (eq 6).7

p-Allyl Palladium Complex.

The dimethyl ester of N-(ethoxycarbonyl)kainic acid forms a p-allyl palladium complex upon treatment with (1) followed by conversion to the more stable chloride complex.2 This p-allyl complex reacts with the anion of t-butyl acetoacetate to afford the alkylated product (eq 7).8

Related Reagents.

Palladium(II) Acetate is similar to palladium(II) trifluoroacetate. Comparable results are obtained in most of the reactions, except acetate is a better nucleophile than trifluoroacetate.

1. Stephenson, T. A.; Morehouse, S. M.; Powell, A. R.; Heffer, J. P.; Wilkinson, G. JCS 1965, 3632.
2. Trost, B. M.; Metzner, P. J. JACS 1980, 102, 3572.
3. Riahi, A.; Cossy, J.; Muzart, J.; Pete, J. P. TL 1985, 26, 839.
4. Matsuura, A.; Ito, Y.; Matsuura, T. JOC 1985, 50, 5002.
5. McMurry, J. E.; Kocovsky, P. TL 1984, 25, 4187.
6. Liebeskind, L. S.; Chidambaram, R.; Mitchell, D.; Foster, B. S. PAC 1988, 60, 27.
7. Takacs, J. M.; Chandramouli, S. V. JOC 1993, 58, 7315.
8. Conway, G. A.; Park, J. S.; Maggiora, L.; Mertes, M. P.; Galton, N.; Michaelis, E. K. JMC 1984, 27, 52.

Michael H. Chen

Parke-Davis Pharmaceutical Research, Ann Arbor, MI, USA

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