The selective oxidation of alcohols is one of the most challenging reactions in green chemistry. [1] Although a number of methods have been developed, the search for new, facile, cost-effective, and environmentally benign procedures that avoid the use of a large excess of toxic and expensive stoichiometric metal oxidants has attracted substantial interest. [2,3] An attractive method is the direct oxidation of alcohols-promoted by reusable heterogeneous catalysts-using air or molecular oxygen (O 2 ) under solventfree conditions or (in the case of solid alcohols) in green organic solvents. [4] Ideally, the reaction should also be performed under mild conditions (preferably at room temperature) for the synthesis of complex, thermolabile compounds, which are typical in fine chemistry. Satisfactory results were attained in only very few cases, in which a large excess of base additives was required, and this was usually achieved at the expense of selectivity. [5,6] Therefore, the development of excellent reusable catalysts for liquid-phase aerobic oxidation of alcohols under mild conditions would constitute a breakthrough in both green chemistry and organic synthesis.
Recently, supported gold nanoparticles have attracted considerable attention because of their extraordinarily high activity and selectivity. [7] The outstanding catalytic ability of gold is related to the size and shape of the nanoparticles, the degree of coordinative unsaturation of the gold atoms, and the interactions between gold and the oxide support. [8, 9] Although several gold systems have been reported for the catalysis of alcohol oxidation reactions, in most cases they have been applied at temperatures above 100 8C. [10] Dehydrogenation is known to be the rate-limiting step in the oxidation of alcohols on various noble metals. [11][12][13] Therefore, the combination of gold nanoparticles with a suitable support (characterized by an exceptional alcohol-dehydrogenation activity) may allow the fabrication of new, versatile gold catalysts that could be used for liquid-phase organic synthesis