2.1.2. 5 Asymmetric Sulfoxidation
The above described Katsuki catalytic system is also effective for the asymmetric oxidation of sulfides to sulfoxides (Scheme 6). The oxidation of aryl alkyl sulfides has been extensively studied with moderate to high enantioselectivity.
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Scheme 6 |
2.1.3 Mn(IV) Reagents as an Oxidant
MnO2 is a useful selective oxidizing reagent in organic synthesis. It is commercially available, and it can also be prepared by the reaction of MnSO4∙4H2O with KMnO4 in aqueous NaOH.
G. Cahiez, M. Alami, Encyclopedia of Reagents for Organic Synthesis, John Wiley and Sons, Inc., L. A. Paquette Ed., New York, 1995, 5, 3229. |
2.1.3.1 Oxidation of Alcohols
MnO2 can selectively oxidize allylic and benzylic alcohols to give the corresponding carbonyl compounds (Scheme 7). The advantage of this method is that the reaction takes place under mild and neutral conditions, also carbon-carbon double and triple bonds are unaffected.
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Scheme 7 |