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Visible‐Light‐Promoted Metal‐Free Synthesis of (Hetero)Aromatic Nitriles from C(sp 3 )−H Bonds **
Author(s) -
Murugesan Kathiravan,
Donabauer Karsten,
König Burkhard
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202011815
Subject(s) - cyanation , chemistry , tetrafluoroborate , combinatorial chemistry , cyanide , catalysis , yield (engineering) , aryl , nitrile , quenching (fluorescence) , organic synthesis , organic chemistry , fluorescence , ionic liquid , materials science , metallurgy , alkyl , physics , quantum mechanics
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.