Combination of ManganeseIII Acetate with 13Dicarbonyl Compounds

Reaction Using 1,3-Diketones

Instead of tris(2,4-pentanedionato)manganese(III), manganese(III) acetate dihydrate was used in the reaction of alkenes with 1,3-dicarbonyl compounds [75,77,78]. The adopted reaction conditions were similar to those for the reaction using tris(2,4-pentanedionato)manganese(III). A mixture of 1,1-diphenylethene, 2,4-pentanedione, and manganese(III) acetate was stirred in acetic acid at room temperature in air until the brown color of Mn(III) turned colorless, giving the same endoperoxide in good yield. This method threw light on the synthesis of the functionalized 1,2-dioxan-3-ols by allowing the choice of combination of various alkenes and 1,3-diketones (Scheme 5).

1-Hydroxy-2,3-dioxabicyclo[4.4.0]decan-7-one, the analog of the root formation inhibitor (G factor) [18-20], was produced by the reaction with 1,3-cyclohexanedione. Other cyclic diketones also afforded the corresponding bicyclic endoperoxides (Scheme 6) [79].

Interestingly, for the reaction of the 1,3-cyclopentanedione, a double endoperoxidation took place and octahydro-3,4,7,8-tetraoxabenz[c]indene-4a,6a-diols were obtained (Scheme 7) [79]. The most characteristic feature in the spectral data was the absence of any carbonyl signals in the 13C NMR spectrum as well as in the IR spectrum. The double endoperoxidation could not stop the corresponding monocyclization stage.

Since treatment of 4-acetyl-3-methyl-6,6-diphenyl-1,2-dioxan-3-ol and 1-hydroxy-4,4-diphenyl-2,3-dioxabicyclo[4.4.0]decan-7-one with a mixture of 1,1-diphenylethene and manganese(III) acetate did not afford any spirodiper-

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