Trivalent Metal Lewis Acids Activate CO₂ in Transfer Hydrogenations.

Area of Science:

• Catalysis
• Green Chemistry
• Organic Synthesis

Background:

• Carbon dioxide (CO2) utilization is crucial for sustainability.
• Bio-derived hydrogen (H2) surrogates offer renewable alternatives.
• Lewis acids (LAs) are versatile catalysts in organic transformations.

Purpose of the Study:

• To investigate the use of trivalent metal MX3 Lewis acids for CO2 hydrogenation.
• To explore the catalytic activity of γ-terpinene as a bio-derived H2 surrogate.
• To develop efficient tandem reactions for synthesizing N-formamides and heterocycles from CO2.

Main Methods:

• Catalytic hydrogenation of CO2 using γ-terpinene and MX3 LAs.
• Tandem hydrogenation-coupling reactions for N-formamide synthesis.
• In situ transfer formylation and cyclization for heterocycle synthesis.
• Density functional theory (DFT) calculations to elucidate the reaction mechanism.

Main Results:

• MX3 LAs effectively catalyze CO2 hydrogenation to formate using γ-terpinene.
• Tandem reactions yield up to 91% N-formamides and 95% heterocycles.
• The catalytic system operates efficiently at low pressure (4 bar) and 130°C.
• DFT calculations confirm CO2 activation by MX3 LAs, enabling direct hydride transfer from γ-terpinene.

Conclusions:

• Trivalent metal Lewis acids demonstrate a triple role in CO2 activation, tandem coupling, and transfer formylation.
• This approach offers a sustainable pathway for CO2 hydrogenation and valorization.
• The use of bio-derived γ-terpinene aligns with green chemistry principles.
• The developed methodology enables the synthesis of valuable chemicals from renewable feedstocks and captured CO2.