Gold Supported on Nanocrystalline β‐Ga₂O₃ as a Versatile Bifunctional Catalyst for Facile Oxidative Transformation of Alcohols, Aldehydes, and Acetals into Esters

Abstract

The less steps, the better: Deposition of gold nanoparticles onto nanocrystalline β‐Ga2O3 results in the formation of a solid bifunctional catalyst that can allow facile, additive‐free, aerobic oxidation of primary alcohols, aldehydes, and acetals into their respective esters in good‐to‐excellent yields (see scheme), providing an environmentally benign approach for the direct synthesis of carboxylic esters.

Oxidant‐Free Dehydrogenation of Alcohols Heterogeneously Catalyzed by Cooperation of Silver Clusters and Acid–Base Sites on Alumina

“…To achieve environmental and economical acceptability, much effort has been devoted to the development of transition-metalcatalyzed oxidation of alcohols with environmentally friendly oxidants (such as oxygen, hydrogen peroxide, or alkenes) that avoid the use of large excesses of toxic and expensive stoichiometric metal oxidants. [3][4][5][6][7][25][26][27][28][29][30] From the viewpoint of atom efficiency and safety of the reaction, an oxidant-free catalytic dehydrogenation of alcohols to carbonyl compounds and molecular hydrogen would be ideal. Several recent reports show oxidant-free alcohol dehydrogenation with PGM catalysts (ruthenium [31][32][33][34][35] and iridium [36] complexes and heterogeneous ruthenium catalysts [37][38][39] ).…”

Recent advances in the heterogeneously catalysed aerobic selective oxidation of alcohols

“…42,43 Gold nanoclusters on gallia polymorphs have also proven to be versatile green catalysts for the oxidative esterification of several alcohols. 44,45 Early work by Hutchings demonstrated the potential of dispersed gold to selectively oxidise alcohols under solvent-free conditions, an important step in achieving a green process. 46 Gold on Cs 2 CO 3 also exhibits excellent selectivity for the room temperature oxidation of primary alcohols to their corresponding aldehyde, reducing the net energy input.…”

Direct Synthesis of Methyl Propionate from n-Propyl Alcohol and Methanol Using Gold Catalysts

“…The first step could be the ratedetermining step since no propyl aldehyde, hemiacetals or acetals is detected during the reaction, so propyl aldehyde, hemiacetals or acetals may rapidly react further. The base additive which can promote the abstraction of hydrogen in [20], hemiacetal formation from aldehydes and alcohols is a facile reaction due to the good electrophilic properties of aldehydes and nucleophilic properties of alcohols, and may not require a catalyst. Therefore, propanoic acid can not be formed because propyl aldehyde can rapidly react with methanol and n-propyl alcohol to form methyl propionate and propyl propionate.…”

“…According to Su et al [20], facile oxidative transformation of alcohols, aldehydes, and acetals into esters has been carried out over Au/b-Ga 2 O 3 with high activity and selectivity. In this paper, supported gold catalysts prepared by DP method are used in the oxidation of n-propyl alcohol dissolved in methanol to synthesize methyl propionate.…”