Bulk Gold-Catalyzed Oxidations of Amines and Benzyl Alcohol Using Amine N-Oxides as Oxidants

Bulk gold powder (similar to 50 mu m) catalyzes the oxidative dehydrogenation of amines to give imines using amine N-oxides (R3N-O) as the oxidant. The reaction of dibenzylamine (PhCH2-NH-CH2Ph) with N-methylmorpholine N-oxide (NMMO) in the presence of gold powder at 60 A degrees C produced N-benzylidenebenzylamine (PhCH=N-CH2Ph) in 96% yield within 24 h. Benzyl alcohol was oxidized by NMMO to benzaldehyde in > 60% yield in the presence of gold powder. Although O-2 was previously shown to oxidize amines in the presence of bulk gold, it is surprising that gold is also capable of catalyzing the oxidation of amines using amine oxides, which are chemically so different from O-2.