Ruthenium-Catalyzed Alkyne Oxidation with Part-Per-Million Catalyst Loadings
Press, New York, 2000; e) P. Y. Bruice, Organic
(see Supporting Information). Under otherwise iden-
tical conditions, replacement of aqueous TBHP with
TBHP in decane (5.0–6.0M, <4% water) in the reac-
tion of 1a only led to the isolation of a small amount
of benzil 2a. On addition of H218O to the above reac-
tion, the desired product was obtained in 89% yield
and 18O was found to be incorporated into the dike-
tone (16O:18Oꢀ56:44 by MS), which confirmed that
water participated as a reagent.
In conclusion, we have disclosed a general, practi-
cal, and simple Ru-catalyzed reaction for transform-
ing alkynes into 1,2-diketones. Salient features of the
method are extremely high catalyst productivity
(TON up to 420,000) and amenability to scale-up,
thus implying the feasibility for industrial/practical ap-
plications. Importantly, no residual ruthenium impuri-
ty was detected by ICP mass analysis in the 1,2-dike-
tone products after recrystallization or column chro-
matographic purification. Further investigations, espe-
cially on details of the mechanism, are ongoing in our
laboratory.
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Experimental Section
General Procedures for Oxidation of Alkynes
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(5.1 mg, 0.02 mmol). Dioxane (1.0 mL) was added via sy-
ringe. A [RuACHTUNGTRENNUNG(cymene)Cl2]2 solution (10 mL, 0.0002 mol/L in
distilled dioxane, 10 ppm) and 100 mL tert-butyl hydroperox-
ide were added into the tube. The reaction mixture was
placed under air, stirred, and heated to 808C for 12 h. It was
then quenched with saturated Na2SO3 solution (consump-
tion of residual TBHP) and reaction mixture was extracted
with ethyl acetate (3ꢂ4 mL). The organic layer was separat-
ed and dried with Na2SO4. Removal of solvent followed by
flash column chromatographic purification afforded the
products.
Acknowledgements
This research was supported by the National Natural Science
Foundation of China (20802047) and the Bureau of Educa-
tion, Jiangsu Province (08KJD150005).
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