A Novel and Efficient Oxidation of Benzyl Alcohols to Benzaldehydes with DMSO Catalyzed by Acids

Abstract

Oxidation of benzyl alcohols to the corresponding aldehydes was achieved by an acid catalyzed DMSO oxidation. When the oxidation was catalyzed by HBr, no side products were detected. In most cases, the yields were excellent. The oxidation rate depends on both the nature and the position of the substituents on the aromatic rings. A tentative mechanism is proposed for the oxidation.

Key words

oxidation - DMSO - HBr - benzyl alcohols - benzaldehydes

References

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9

Typical procedure: A mixture of 557 mg of benzyl alcohol, 0.15 mL of HBr (48%) and 5 mL of DMSO was stirred in an oil bath at 100 ºC. TLC (petroleum ether/diethyl ether, 1:1) was used to indicate the completion of the reaction (3 h). To the reaction mixture were added 5 mL of brine followed by extraction with 30 mL of diethyl ether. The ether layer was washed with brine (5 mL × 4). Evaporation of ether and subsequent bulb to bulb distillation produced 530 mg of benzaldehyde in 95% yield.