Bis(triphenylphosphine)palladium(II) Acetate

Pd(PPh3)2(OAc)2

[14588-08-0]  · C40H36O4P2Pd  · Bis(triphenylphosphine)palladium(II) Acetate  · (MW 749.09)

(catalyst for various reactions, for example coupling reactions, dimerizations, cyclizations, carbonylations, and reductions)

Physical Data: lemon-yellow amorphous crystals; mp 136 °C (dec.).

Solubility: sol acetonitrile, benzene, dioxane, DMF, DMSO, THF; low sol petroleum ether.

Form Supplied in: commercially available solid.

Handling, Storage, and Precautions: store under argon at -18 °C; air and moisture sensitive; hygroscopic.

General Considerations.

This reagent has mainly been used in coupling reactions and cyclizations, but also for reductions, and carbonylations. Although commercially available, the catalyst is easily prepared by mixing Palladium(II) Acetate with an excess of Triphenylphosphine in benzene.1 There is also evidence that mixing Pd(OAc)2 with 2 equiv of PPh3 generates a species with the same properties as Pd(OAc)2(PPh3)2 (1). In most catalytic reactions, complex (1) generates Pd0 in situ, which is the active catalyst.2 Reagents able to do similar reactions as (1) are described in the following text.

Coupling and Dimerization Reactions.

Catalyst (1) has been used to couple and dimerize many types of substrates. For example, isoprene in the presence of (1), Formic Acid, Triethylamine and an alcohol dimerizes to generate predominantly 1,6-diene (2) and 1,7-diene (3) (eq 1). The formic acid serves as a hydrogen donor. These two isomers were used to prepare the terpenes a,b-citronellol and linalool.3 Under similar reaction conditions, alkynes react with iodobenzene to give alkenes.4

Although the most commonly used catalyst for Heck arylation and vinylation reactions5 is Pd(OAc)2, there are several examples where (1) has been used. For example, 2-bromopropene reacts with styrene (eq 2)6a or phenylacetylene (eq 3)6b to yield dienes or enynes, respectively.

Reagent (1) catalyzes the coupling between fluorinated vinyl iodides and 1-alkynes to give excellent yields of fluorinated enynes.7 The use of Dichlorobis(triphenyl-phosphine)palladium(II) (4) and Tetrakis(triphenylphosphine)palladium(0) as catalysts give similar results. Various substituted aryl bromides react with trimethylsilylacetylene in the presence of (1) to give terminal alkynes (eq 4).8 In some cases, (4) has been used in place of (1). The corresponding aryl propargyl alcohols (which are easily converted to terminal alkenes) are made by Tetraethyl Pyrophosphate catalyzed cross-coupling of aryl halides with propargyl alcohol.9

The coupling of aryl iodides with a,b-unsaturated ketones10a,b and aldehydes10c (eq 5) is catalyzed by (1). This reagent nicely catalyzes the coupling of vinyl and aryl triflates with various terminal alkynes in the presence of a base (eq 6).11,12 Addition of n-Bu4NCl increases the yield.

Cyclizations.

Complex (1) catalyzes the cyclization of 1,6-enynes to five-membered rings. Either 1,3- or 1,4-dienes are formed depending on the substituents (eqs 7 and 8).13 When Diacetatobis(tri-o-tolylphosphine)palladium(II) is used the yield increases.

These cyclizations can be performed with full stereocontrol.14 Functionalized butenolides are obtained with high stereo- and regioselectivity in a one-pot hydroarylation cyclization when a,b-alkynic esters are reacted in the presence of formic acid, Tri-n-butylamine, and catalyst (1).15

Reductions.

Vinyl and aryl triflates are reduced in high yields with catalytic amounts of (1).16 The reaction shown in eq 9 is used in a route to angelicin.17

Carbonylations.

If Carbon Monoxide is present in place of formic acid, an insertion of a CO unit into the metal-carbon bond in the intermediate occurs to produce the corresponding acid. Vinyl alcohols and phenols, after conversion to triflates, undergo one-carbon homologation to the corresponding a,b-unsaturated and aromatic acids.18 Vinyl triflates work best with the title catalyst, but with aryl triflates, better results are obtained with Palladium(II) Acetate and 1,1-Bis(diphenylphosphino)ferrocene (dppf) as an added ligand. Oxalic acid esters can be made from alcohols under 20-50 atm of CO employing (1) in stochiometric amounts (4 gave no reaction).19 The use of 1,4-Benzoquinone as a reoxidant makes it possible to use (1) in catalytic amounts. For example, treatment of methanol with 1 mol % of (1) and carbon monoxide at a pressure of 1000 psi and 65 °C gives the methyl ester of oxalic acid in high yield.20


1. Stephenson, T. A.; Morehouse, S. M.; Powell, A. R.; Heffer, J. P.; Wilkinson, G. JCS 1965, 3362.
2. (a) Amatore, C.; Jutand, A.; M'Barki, M. A. OM 1992, 11, 3009. (b) Ozawa, F.; Kubo, A.; Hayashi, T. CL 1992, 2177.
3. Neilan, J. P.; Laine, R. M.; Cortese, N.; Heck, R. F. JOC 1976, 41, 3455.
4. Cacchi, S.; Felici, M.; Pietroni, B. TL 1984, 25, 3137.
5. Heck, R. F. OR 1982, 27, 345.
6. (a) Dieck, H. A.; Heck, R. F. JOC 1975, 40, 1083. (b) Dieck, H. A.; Heck, R. F. JOM 1975, 93, 259.
7. Yang, Z. Y.; Burton, D. J. TL 1990, 31, 1369.
8. (a) Austin, W. B.; Bilow, N.; Kelleghan, W. J.; Lau, K. S. Y. JOC 1981, 46, 2280. (b) Garst, M. E.; McBride, B. J. JOC 1989, 54, 249.
9. Bumagin, N. A.; Beletskaya, I. P.; Ponomaryov, A. B. S 1984, 728.
10. (a) Cacchi, S.; Arcadi, A. JOC 1983, 48, 4236. (b) Cacchi, S.; Palmieri, G. S 1984, 575. (c) Cacchi, S.; La Torre, F.; Palmieri, G. JOM 1984, 268, C48.
11. Cacchi, S.; Morera, E.; Ortar, G. S 1986, 320.
12. Arcadi, A.; Burini, A.; Cacchi, S.; Delmastro, M.; Marinelli, F.; Pietroni, B. R. JOC 1992, 57, 976.
13. (a) Trost, B. M.; Lautens, M. JACS 1985, 107, 1781. (b) Trost, B. M.; Chung, J. Y. L. JACS 1985, 107, 4586.
14. Trost, B. M.; Lautens, M.; Chan, C.; Jebaratnam, D. J.; Mueller, T. JACS 1991, 113, 636.
15. Arcadi, A.; Bernocchi, E.; Burini, A.; Cacchi, S.; Marinelli, F.; Pietroni, B. T 1988, 44, 481.
16. Cacchi, S.; Morera, E.; Ortar, G. TL 1984, 25, 4821.
17. Peterson, G. A.; Kunng, F. A.; McCallum, J. S.; Wulff, W. D. TL 1987, 28, 1381.
18. Cacchi, S; Lupi, A. TL 1992, 33, 3939.
19. Rivetti, F.; Romano, U. JOM 1978, 154, 323.
20. Current, S. P. JOC 1983, 48, 1779.

Roberto G. P. Gatti & Jan-E. Bäckvall

Uppsala University, Sweden



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