Direct Photoexcitation of Ethynylbenziodoxolones: An Alternative to Photocatalysis for Alkynylation Reactions

• Published in: Angewandte Chemie International Edition Vol. 60; no. 44; pp. 23827 - 23834
• Main Authors: Amos, Stephanie G. E., Cavalli, Diana, Le Vaillant, Franck, Waser, Jerome
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 25-10-2021; John Wiley and Sons Inc
• Edition: International ed. in English
• Subjects: Alcohols; alkynes; Amines; Aromatic compounds; hypervalent iodine; Imines; Irradiation; Light irradiation; Oxalates; Oxalic acid; Oxidants; Oxidizing agents; Photocatalysis; photochemistry; Photoexcitation; quaternary centers; Radiation; Reagents; Salts; synthetic methods; Traps
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202110257

Ethynylbenziodoxolones (EBXs) are commonly used as radical traps in photocatalytic alkynylations. Herein, we report that aryl‐substituted EBX reagents can be directly activated by visible light irradiation. They act as both oxidants and radical traps, alleviating the need for a photocatalyst in several reported EBX‐mediated processes, including decarboxylative and deboronative alkynylations, the oxyalkynylation of enamides and the C−H alkynylation of THF. Furthermore, the method could be applied to the synthesis of alkynylated quaternary centers from tertiary alcohols via stable oxalate salts and from tertiary amines via aryl imines. A photocatalytic process using 4CzIPN as an organic dye was also developed for the deoxyalkynylation of oxalates.
Aryl ethynylbenziodoxolones (ArEBXs) can be directly activated by visible light irradiation. In the excited state, ArEBXs act as strong oxidants, alleviating the need for a photocatalyst in decarboxylative and deboronative alkynylations, the oxyalkynylation of enamides, and the C−H alkynylation of THF.