Visible‐Light‐Promoted Metal‐Free Synthesis of (Hetero)Aromatic Nitriles from C(sp3)−H Bonds. Issue 5 (1st December 2020)

• Record Type: Journal Article
• Authors: Murugesan, Kathiravan; Donabauer, Karsten; König, Burkhard
• Is Part Of: Angewandte Chemie international edition. Volume 60:Issue 5(2021)
• Page Start: 2439
• Page End: 2445
• Publication Date: 2020-12-01
• Subjects: ammoxidation -- C−H functionalization -- methylarenes -- nitriles -- photoredox catalysis; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202011815
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: The metal‐free activation of C(sp 3 )−H bonds to value‐added products is of paramount importance in organic synthesis. We report the use of the commercially available organic dye 2, 4, 6‐triphenylpyrylium tetrafluoroborate (TPP) for the conversion of methylarenes to the corresponding aryl nitriles via a photocatalytic process. Applying this methodology, a variety of cyanobenzenes have been synthesized in good to excellent yield under metal‐ and cyanide‐free conditions. We demonstrate the scope of the method with over 50 examples including late‐stage functionalization of drug molecules (celecoxib) and complex structures such as l ‐menthol, amino acids, and cholesterol derivatives. Furthermore, the presented synthetic protocol is applicable for gram‐scale reactions. In addition to methylarenes, selected examples for the cyanation of aldehydes, alcohols and oximes are demonstrated as well. Detailed mechanistic investigations have been carried out using time‐resolved luminescence quenching studies, control experiments, and NMR spectroscopy as well as kinetic studies, all supporting the proposed catalytic cycle. Abstract : C(sp 3 )−H bonds have been converted to cyano derivatives under metal‐ and cyanide‐free condition in the presence of visible light and an organic dye. Potential applications of this method in the late‐stage transformation of complex drug molecules, steroid derivatives, and gram‐scale reactions have been described.