Propargylic alcohols, manganese dioxide

Isoxazole-5-carbaldehyde was prepared by the manganese dioxide oxidation of 5-hydroxymethylisoxazole (67T4697), the latter being formed from sodium fulminate and propargyl alcohol in greater than 90% yield. 

The procedure described is that of Wille and Saffer. Propiolaldehyde has also been prepared by the oxidation of propargyl alcohol using ammonium dichromate or manganese dioxide in 10% sulfuric acid. Propiolaldehyde has also been prepared by warming the dimethyl or diethyl acetal with dilute sulfuric acid. ... 

Oxidation of sensitive divinyl alcohol 20 to dienone 4 is achieved by treatment with activated manganese dioxide. Commercially available active Mn02 21 is a synthetic nonstoichiometric hydrated material. This reagent provides mild conditions for oxidation of allylic, propargylic, and benzylic alcohols.10... 

Terminal arylalkynes can be prepared by oxidation-decarbonylation of 3-arylpropargyl alcohols using manganese dioxide in the presence of alkali. The corresponding arylpiopargyl dcohols are available by palladium-catalysed cross-coupling of aryl halides with commercial propargyl alcohol. The yield of the second step can be improved by the addition of a phase-transfer catalyst (18-crown-6 Scheme 18). ... 

N.B. Propargylaldehyde attacks the mucous membranes of the eyes and nose. It can also be prepared by oxidation of propargyl alcohol with active manganese dioxide.10... 

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