Manganese(III) Acetylacetonate

[14284-89-0]  · C15H21MnO6  · Manganese(III) Acetylacetonate  · (MW 352.30)

(one-electron oxidant used to oxidize phenols, b-dicarbonyl compounds, and thiols to the corresponding radical)

Physical Data: lustrous brown crystalline solid; mp 172 °C.1

Solubility: slightly sol water; sol acetone, benzene, chloroform, ether, ethanol, ethyl acetate.1

Manganese(III) acetylacetonate, Mn(acac)3, was reported to be the most useful manganese(III) reagent for oxidative coupling of phenols.2,3 For instance, 2-naphthol is oxidized to 2,2-binaphthol in 69% yield in acetonitrile or carbon disulfide (eq 1).2 Mn(acac)3 has been used for the intramolecular oxidative coupling of a series of a,o-bis(3,4-dimethoxyphenyl)alkanes.4 Anodic oxidation gives somewhat higher yields than Mn(acac)3. Intramolecular oxidative coupling with Mn(acac)3 has been used as a key step in the synthesis of (+)- and (-)-galanthamine (eq 2).5 Mn(acac)3 induces the oxidative cyclization of a phenolic oxime to give the spiroisoxazoline in 50% yield (eq 3).6 Mn(acac)3 in carbon disulfide oxidizes aryl, alkyl, and benzyl thiols at rt in 1-2 h to disulfides in 85-99% yield.7

In the absence of a more readily oxidizable substrate, Mn(acac)3 reacts with alkenes8,9 and electron-rich arenes10 to give radicals that are oxidized by Mn(acac)3 to give the final product (eqs 4 and 5). The acetylacetone radical is probably not an intermediate in these reactions.11

Peroxy hemiacetals are prepared by oxidative addition of Mn(acac)3 to alkenes in the presence of oxygen (eq 6).12

1. Gmelin Handbuch der Anorganischen Chemie: Mangan D1; Springer: Berlin, 1979; pp 85-98.
2. Dewar, M. J. S.; Nakaya, T. JACS 1968, 90, 7134.
3. Omote, Y.; Takizawa, Y.; Sugiyama, N. BCJ 1972, 45, 2882.
4. Rolan, A.; Parker, V. D. JOC 1974, 39, 1014.
5. Shimizu, K.; Tomioka, K.; Yamada, S.; Koga, K. CPB 1978, 26, 3765.
6. Forrester, A. R.; Thomson, R. H.; Woo, S.-O. JCS(P1) 1975, 2340.
7. Nakaya, T.; Arabori, H.; Imoto, M. BCJ 1970, 43, 1888.
8. Nishino, H. BCJ 1985, 58, 1922.
9. Nishino, H.; Yoshida, T.; Kurosowa, K. BCJ 1991, 64, 1097.
10. Citterio, A.; Fancelli, D.; Santi, R.; Pagani, A.; Bonsignore, S. G 1988, 118, 405.
11. Snider, B. B.; Patricia, J. J.; Kates, S. A. JOC 1988, 53, 2137.
12. Nishino, H. Tategami, S.; Yamada, T.; Korp, J. D.; Kurosawa, K. BCJ 1991, 64, 1800.

Barry B. Snider

Brandeis University, Waltham, MA, USA

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