Overcoming the Barrier to Intermolecular Alkoxy Radical Reactivity: Proton-Coupled Electron Transfer-Mediated Alkene...

Area of Science:

• Organic Chemistry
• Photocatalysis
• Radical Chemistry

Background:

• Proton-coupled electron transfer (PCET) facilitates alkoxy radical formation.
• Intermolecular reactions of alkoxy radicals are challenging due to instability and competing pathways like β-scission.
• Developing methods for controlled intermolecular trapping of these radicals is crucial.

Purpose of the Study:

• To develop an efficient intermolecular anti-Markovnikov hydroetherification method.
• To overcome the challenges associated with alkoxy radical reactivity.
• To design a novel photocatalyst for controlled PCET-initiated reactions.

Main Methods:

• Utilized proton-coupled electron transfer (PCET) for hydroetherification.
• Employed enoxysilanes and enamides as nucleophilic olefin traps.
• Designed and used a novel organophotocatalyst with stimulus-gated redox activation via hydrogen bonding.
• Investigated diverse alcohol precursors under mild conditions with low catalyst loadings.

Main Results:

• Achieved efficient intermolecular hydroetherification using alkoxy radical intermediates.
• Demonstrated successful trapping of radicals with nucleophilic olefins.
• Showcased the catalyst's ability to activate upon hydrogen bonding with alcohols, preventing off-target oxidation.
• Confirmed reactivity with alcohol substrates prone to side reactions like β-scission.

Conclusions:

• The developed organophotocatalyst enables efficient intermolecular hydroetherification via a hydrogen bond-activated PCET mechanism.
• This method provides a robust route for generating C-O bonds from alcohols.
• The findings advance the control over reactive radical intermediates in organic synthesis.