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Synthesis of Sterically Hindered Primary Amines by Concurrent Tandem Photoredox Catalysis

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journal contribution
posted on 06.01.2020, 13:35 authored by Michael C. Nicastri, Dan Lehnherr, Yu-hong Lam, Daniel A. DiRocco, Tomislav Rovis
Primary amines are an important structural motif in active pharmaceutical ingredients (APIs) and intermediates thereof, as well as members of ligand libraries for either biological or catalytic applications. Many chemical methodologies exist for amine synthesis, but the direct synthesis of primary amines with a fully substituted α carbon center is an underdeveloped area. We report a method which utilizes photoredox catalysis to couple readily available O-benzoyl oximes with cyano­arenes to synthesize primary amines with fully substituted α-carbons. We also demonstrate that this method enables the synthesis of amines with α-trifluoromethyl functionality. Based on experimental and computational results, we propose a mechanism where the photocatalyst engages in concurrent tandem catalysis by reacting with the oxime as a triplet sensitizer in the first catalytic cycle and a reductant toward the cyano­arene in the second catalytic cycle to achieve the synthesis of hindered primary amines via heterocoupling of radicals from readily available oximes.