Vapour-phase gold-surface-mediated coupling of aldehydes with methanol

Area of Science:

• Catalysis and Materials Science
• Organic Synthesis
• Sustainable Chemistry

Background:

• Selective coupling of oxygenates is vital for synthesizing chemicals, including alternative fuels.
• Gold nanoparticles (Au NPs) are increasingly recognized for their catalytic potential in oxidation reactions.

Purpose of the Study:

• To develop a general and highly selective process for ester synthesis via the coupling of aldehydes and methanol.
• To investigate the role of oxygen-covered gold nanoparticles on Au(111) in mediating this transformation.
• To elucidate the reaction mechanism and factors influencing selectivity.

Main Methods:

• Utilizing oxygen-covered metallic gold nanoparticles supported on Au(111) as the catalyst.
• Performing cross-coupling reactions between various aldehydes (formaldehyde, acetaldehyde, benzaldehyde, benzeneacetaldehyde) and methanol.
• Conducting reactions below room temperature to promote selectivity.

Main Results:

• Achieved highly selective synthesis of methyl esters from the cross-coupling of methanol with diverse aldehydes.
• Demonstrated the catalytic activity of oxygen-covered Au(111) nanoparticles at sub-room temperatures.
• Identified nucleophilic attack by a surface-formed methoxy intermediate on aldehydes as the key to high ester selectivity, suppressing competing combustion.

Conclusions:

• Oxygen-covered gold nanoparticles on Au(111) provide an efficient catalytic system for selective ester synthesis.
• The reaction mechanism favors ester formation through methoxy intermediates, highlighting the catalyst's role in controlling selectivity.
• This approach offers a valuable pathway for producing esters, relevant to fine chemical synthesis and alternative fuel development.