1.3.6 Pyridinium Dichromate (PDC) Oxidation
Pyridinium dichromate (PDC), (C5H5NH+)2Cr2O72-, oxidizes alcohols under neutral condition without affecting other functional groups (Scheme 7). Primary alcohols are oxidized to aldehydes with excellent yield. Allylic alcohol can be oxidized to α,β-unsaturated carbonyl compounds. Excellent yields are obtained by the oxidation of secondary alcohols by using trimethyl silyl peroxide and PDC (Scheme 8).
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Scheme 7 |
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Scheme 8 |
1.3.7 Oxidation of Alkenes
Chromium based reagents are used for the oxidation of alkenes to afford α,β-unsaturated carbonyl compounds and epoxides depending the nature of substrates and reactions conditions. For example, Na2Cr2O4 has been used in acetic anhydride for allylic oxidation of cyclic alkenes to afford α,β-unsaturated carbonyl compounds (Scheme 9).
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Scheme 8 |