Solvent-Free Oxidation of Primary Carbon-Hydrogen Bonds in Toluene Using Au-Pd Alloy Nanoparticles

Abstract

Selective oxidation of primary carbon-hydrogen bonds with oxygen is of crucial importance for the sustainable exploitation of available feedstocks. To date, heterogeneous catalysts have either shown low activity and/or selectivity or have required activated oxygen donors. We report here that supported gold-palladium (Au-Pd) nanoparticles on carbon or TiO(2) are active for the oxidation of the primary carbon-hydrogen bonds in toluene and related molecules, giving high selectivities to benzyl benzoate under mild solvent-free conditions. Differences between the catalytic activity of the Au-Pd nanoparticles on carbon and TiO(2) supports are rationalized in terms of the particle/support wetting behavior and the availability of exposed corner/edge sites.

Solvent-free aerobic oxidation of hydrocarbons and alcohols with Pd@N-doped carbon from glucose

“…The aerobic oxidation of toluene is a challenging task in the raw material transformation 33 . In the case of toluene, the Pd catalyst can promote the solvent-free oxidation with benzaldehyde and benzyl benzoate as main products (TOF ¼ 4.4 h À 1 ) (Entry 7, Table 3).…”

“…The aerobic oxidation of hydrocarbons to more functional compounds (aldehydes, ketones, acids or esters), one of the most important processes in petrochemical transformation, has been seldom reported by Pd catalysts 31,32 . Recently, the strategy of Au-Pd alloys have enabled O 2 to be used as oxidant in the catalytic oxidation of toluene 33 . However, discovery of active heterogeneous Pd catalysts for the selective oxidation of sp 3 C-H bonds by atmosphere air is still of great importance.…”

Catalysis using colloidal-supported gold-based nanoparticles

“…In the case of toluene, the efficient transformation of toluene to benzyl benzoate (90-95 % selectivity) was achieved at mild conditions (120-160°C, 10 bar of O 2 ) using molecular oxygen or tertbutyl hydroperoxide as oxidant (Fig. 6) [34]. Mechanistic studies revealed that the oxidation proceeds via the initial formation of benzyl alcohol, which is rapidly oxidised to benzaldehyde.…”

Visible Light Promoted Allylic C–H Oxidation

“…[3,4] An oxidation reaction of special interest is the allylic oxidation that allows the conversion of alkenes into allyl alcohols or enones. [5] Allylic oxidations via the direct sp 3 C-H bond activation of alkenes and alkylarenes to the corresponding α, β-unsaturated enones and carbonyl compounds are important transformations with a wide variety of industrial applications [6,7] including the synthesis of drug precursors and building blocks in many organic syntheses.…”