Switchable Decarboxylation by Energy- or Electron-Transfer Photocatalysis

Area of Science:

• Organic Chemistry
• Photocatalysis
• Green Chemistry

Background:

• Kolbe dimerization and Hofer-Moest reactions are electrochemical methods for carboxylic acid transformation.
• These methods construct C-C and C-heteroatom bonds via decarboxylation but require high current density, limiting functional group compatibility.
• Switching between reaction pathways (radical or carbocation intermediates) is possible via electrode selection.

Purpose of the Study:

• To develop a switchable and functional group-compatible photocatalytic method for carboxylic acid transformations.
• To control reaction pathways (energy transfer vs. single-electron transfer) using different photocatalysts.
• To achieve selective synthesis of multiple products from a single carboxylic acid substrate.

Main Methods:

• Utilized photocatalysis for decarboxylative transformations of activated carboxylic acids.
• Employed an organo-photocatalyst for the energy transfer (EnT) pathway.
• Used a ruthenium photoredox catalyst for the single-electron transfer (SET) pathway.
• Coupled resulting radical intermediates with olefins to perform multicomponent reactions.

Main Results:

• The EnT pathway yielded 1,2-diarylethanes from arylacetic acids.
• The SET pathway facilitated the construction of ester scaffolds with arylmethyl moieties.
• Successfully synthesized four distinct products from a single carboxylic acid precursor.
• Demonstrated switchable reactivity and high functional group tolerance.

Conclusions:

• Photocatalytic decarboxylative transformations offer a versatile and compatible alternative to electrochemical methods.
• Controlling photocatalyst and reaction pathway (EnT vs. SET) allows selective product formation.
• This approach enables efficient, cost-effective synthesis of multiple compounds from simple substrates.