Manganese dioxide(MnO2) oxidizing Reagent shows excellent Selectivity towards allylic and benzylic alcohols over other alcoholic functions. MnO2 is not affecting olefinic and acetylenic bonds. The reason reaction takes place under mild neutral conditions is an advantage to this reagent.
Saturated alcohols are not oxidized by MnO2 under ordinary conditions. Hence MnO2 shows excellent Selectivity towards allylic and benzylic alcohols.
MnO2 oxidizes primary alcohols to aldehydes and secondary alcohols to ketones.
Applications Manganese dioxide(MnO2) Reagent Selectivity
Selectivity towards allylic and benzylic alcohols over saturated alcohols
saturated alcohols are not affected under normal conditions
MnO2 is not affecting olefinic and acetylenic bonds due to mild neutral conditions.
MnO2 sensitive to steric hinderence, oxidation prefers less crowded alcohol over crowded.
Using excess MnO2 saturated alcohols can also be oxidized
MnO2 cleaves 1,2 diols to aldehydes and ketones.
First step: protection of dialcohols selectively using 2,2 dimethoxypropane to form Acetals. Alcohols need to be on the same face to avoid strain while forming cyclic acetals.
Second step: selective oxidation of allylic alcohol using MnO2 to form carbonyl compound. Followed by acid hydrolysis to remove protecting group 2,2 dimethoxypropane.
Also read Birch Reduction