Copper(II) Acetylacetonate

[13395-16-9; 46369-53-3]  · C10H14CuO4  · Copper(II) Acetylacetonate  · (MW 261.76)

(catalyst for decomposition of diazo compounds1-4 and for coupling reactions of organometallics with organic halides and sulfones9-11,13)

Alternate Names: cupric acetylacetonate; bis(2,4-pentanedionato-O,O)copper.

Physical Data: crystalline solid, mp 284-288 °C (dec); structural studies have been reported.14

Solubility: sol CHCl3; sl sol alcohols.

Form Supplied in: commercially available solid.

Preparative Methods: several available, e.g. addition of acetylacetone (2,4-Pentanedione) to an aq soln of Cu(NH3)42+ prepared from copper(II) nitrate trihydrate and conc aq NH3.15

Purification: recrystallization from CHCl3.15a

Handling, Storage, and Precautions: irritant.

Decomposition of Diazo Compounds.

Copper(II) acetylacetonate has been used to catalyze the decomposition of diazo compounds in preparations of carbenoids. The influence of copper chelates on carbene reactions is due to coordination with the diazoalkane as a fifth ligand to give a complex which decomposes to a copper-carbene complex. Copper(I) Acetylacetonate was also reported to have similar functionality. The reaction mechanism has been studied, based on the decomposition of Diphenyldiazomethane (eqs 1 and 2).1

A variety of thermal cyclizations utilize copper(II) acetylacetonate-catalyzed carbene reactions (eqs 3-5).2-6

Copper(II) acetylacetonate catalyzes the reaction of 2-azido-1,4-quinones with conjugated alkadienyl side chains, giving dihydropyrroloindoloquinones or dihydropyrroloquinolinoquinones, which are not produced by uncatalyzed pyrolysis or photochemical reactions (eq 6).7 In this example, Cu(acac)2 showed greater activity then many other acetylacetonate complexes or copper powder.

Copper(II) acetylacetonate has been used as a catalyst for the coupling of bis-diazo ketones to enediones (eq 7).8

Coupling Reactions.

The reactions of allylic sulfones and Grignard reagents take place readily under Cu(acac)2 catalysis (eq 8).9,10 The carbon-carbon bond-forming method is useful for introducing medium-length alkyl groups, e.g. butyl, hexyl, and octyl, and also succeeds with allylic chloride and acetate substrates at or below 20 °C.

The reagent also catalyzes the stereospecific cross coupling of alkenyldicyclohexylboranes with allylic or alkynic halides (eq 9).11 (E)-Enynes and 1,4-dienes are produced in good yields and high isomeric purity; Tetrakis(triphenylphosphine)palladium(0) gives comparative results in similar or better yields.11

The coupling reaction of Reformatsky reagents with allylic halides can also be accomplished in high yield under the catalysis of copper(II) acetylacetonate.13

Reductive Reactions.

It was reported that aromatic nitro compounds can be reduced to the corresponding amines by Sodium Borohydride-Cu(acac)2 in high yield.12

Related Reagents.

Bis(acetylacetonato)zinc(II); Copper(I) Acetylacetonate; Tris(acetylacetonato)indium; Manganese(III) Acetylacetonate; Nickel(II) Acetylacetonate; Palladium(II) Acetylacetonate; 2,4-Pentanedione; Tris(acetylacetonato)iron(III); Vanadyl Bis(acetylacetonate).

1. Nozaki, H.; Takaya, H.; Moriuti, S.; Noyori, R. T 1968, 24, 3655.
2. Huisgen, R.; Binsch, G.; Ghosez, L. CB 1964, 97, 2628.
3. Fujita, M.; Hiyama, T.; Kondo, K. TL 1986, 21, 2139.
4. Hudlicky, T.; Koszyk, F. J.; Kutchan, T. M.; Sheth, J. P. JOC 1980, 45, 5020.
5. Hudlicky, T.; Short, R. P. JOC 1982, 47, 1522.
6. Hudlicky, T.; Natchus, M. G.; Sinai-Zingde, G. JOC 1987, 52, 4641.
7. Maruyama, K.; Nagai, N.; Naruta, Y. CL 1987, 97.
8. Kulkowit, S.; McKervey, M. A. JCS(C) 1978, 1069.
9. Julia, M.; Righin-Topie, A.; Verpeaux, J. T 1983, 39, 3283.
10. Julia, M.; Verpeaux, J. T 1983, 39, 3289.
11. Hoshi, M.; Masuda, Y.; Arase, A. BCJ 1983, 56, 2855.
12. Hanaya, K.; Muramatsu, T.; Kudo, H. JCS(P1) 1979, 2409.
13. Gaudemar, M. TL 1983, 24, 2749.
14. For example: (a) Ferguson, J. JCP 1961, 34, 1609. (b) Thompson, D. W. Struct. Bonding 1971, 9, 27.
15. (a) Jones, M. M. JACS 1959, 81, 3188. (b) Mehrotra, R. C.; Gora, R.; Gaur, D. P. The Chemistry of beta-Diketonates and Allied Derivatives; Academic: London, 1978.

Edward J. Parish & Shengrong Li

Auburn University, AL, USA

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