·
Palladium complexes containing electron rich ligands such as phenanthroline have been found to catalyze the aerobic oxidation of secondary alcohols to give ketones (Scheme 3).
Mechanism
The palladium catalyzed oxidation of alcohols to carbonyl compounds with molecular oxygen can be explained as shown in Scheme 4. The palladium complex acts as an active catalyst and oxidizes the alcohols to carbonyl compounds. The reduced Pd(0) is reoxidized to Pd(II) by molecular oxygen to complete the catalytic cycle.
 |
Scheme 5 |
1.7.3 Ruthenium Catalyzed Reactions
1.7.3.1 Oxidation of Alcohols
Ruthenium catalyzed aerobic oxidation of alcohol has been extensively studied. RuCl3·H2O has been used for the oxidation of secondary alcohols to give ketones in the presence of oxygen (Scheme 6).
 |
Scheme 6 |
Catalytic amount of RuCl2(PPh3)2 in combination with benzoquinone has been shown as an effective system for the oxidation of aliphatic, allylic and benzylic alcohols to provide aldehydes or ketones in the presence of molecular oxygen (Scheme 7).
 |
Scheme 7 |
1.7.3.2 Oxidation of Amines
Binuclear ruthenium catalyst has been used for the oxidation of secondary amines to provide imines in presence of molecular oxygen (Scheme 8).
 |
Scheme 8 |