Light-Promoted Radical Arylation of Nitrones with Triazenes

Area of Science:

• Organic Chemistry
• Photochemistry
• Radical Reactions

Background:

• Aryl radicals are valuable synthetic intermediates but often require harsh conditions or specialized reagents for generation.
• Hydroarylation of nitrones offers a pathway to substituted hydroxylamines, important motifs in medicinal chemistry and materials science.
• Developing milder, more efficient methods for aryl radical generation and subsequent functionalization is an ongoing challenge.

Purpose of the Study:

• To describe a novel method for generating aryl radicals from aryltriazenes.
• To utilize these aryl radicals for the direct hydroarylation of nitrones.
• To achieve this transformation under mild, visible-light conditions.

Main Methods:

• Aryltriazenes were employed as precursors for aryl radical generation.
• The reaction was initiated using visible-light irradiation.
• Sodium ascorbate served as the reductant, and acetic acid as the proton source.

Main Results:

• The hydroarylation of nitrones with aryl radicals was successfully achieved, yielding substituted hydroxylamines.
• A key feature is the light-induced E to Z isomerization of triazenes, enhancing reactivity without a photocatalyst.
• The method demonstrated effectiveness with electron-rich and neutral aryl triazenes.

Conclusions:

• Aryltriazenes are effective and safe precursors for generating aryl radicals under visible-light irradiation.
• The developed method provides a photocatalyst-free route for the direct hydroarylation of nitrones.
• This approach offers a mild and efficient pathway to valuable substituted hydroxylamine products.