Porous Silica Beads Supported TEMPO and Adsorbed NOx (PSB-TEMPO/NOx): An Efficient Heterogeneous Catalytic System for the Oxidation of Alcohols under Mild Conditions

The combination of NOx gas which is stored in the pore canals of porous silica beads (PSB) with a heterogeneous catalyst, PSB-supported 2,2,6,6-tetramethylpiperdine 1-oxyl (PSB-TEMPO, 1), afforded a highly efficient, widely applicable, and efficiently recyclable approach for the selective aerobic oxidation of alcohols. This novel catalytic system (PSB-TEMPO/NOx) can be employed in the oxidation of a wide range of alcohols to their corresponding aldehydes and ketones with selectivities as high as 99% at complete conversions under mild conditions. O-2 is the terminal oxidant. PSB-TEMPO can be recycled for more than 10 times without significant loss of activity.