Alkynylation of Csp2 (O)–H Bonds Enabled by Photoredox‐Mediated Hydrogen‐Atom Transfer

• Published in: Angewandte Chemie International Edition Vol. 56; no. 46; pp. 14723 - 14726
• Main Authors: Mukherjee, Satobhisha, Garza‐Sanchez, R. Aleyda, Tlahuext‐Aca, Adrian, Glorius, Frank
• Format: Journal Article
• Language: English
• Published: Germany 13.11.2017
• Subjects: carbonyl radicals; C−H activation; hydrogen-atom transfer; hypervalent compounds; photocatalysis; C−H activation; photocatalysis; hypervalent compounds; hydrogen-atom transfer; carbonyl radicals
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201708037

The development of new hydrogen‐atom transfer (HAT) strategies within the framework of photoredox catalysis is highly appealing for its power to activate a desired C−H bond in the substrate leading to its selective functionalization. Reported here is the first photoredox‐mediated hydrogen‐atom transfer method for the efficient synthesis of ynones, ynamides, and ynoates with high regio‐ and chemoselectivity by direct functionalization of Csp2 (O)−H bonds. The broad synthetic application of this method has been demonstrated by the selective functionalization of C(O)−H bonds within complex molecular scaffolds. Tip your HAT: A photoredox‐catalyzed hydrogen‐atom transfer (HAT) method has been developed for the successful generation of carbonyl radicals from aldehydes and analogous compounds with an XC(O)−H (X=N, O) group. The successful trapping of the carbonyl radicals with ethynylbenziodoxolone (EBX) reagents provides a route for the synthesis of ynones, ynamides, and ynoates from readily available starting materials.