Allylic amination and carbon–carbon double bond transposition catalyzed by cobalt(II) azodioxide complexes

• Main Authors: Kylin A. Emhoff, Ahmed M.H. Salem, Lakshmi Balaraman, Drew M. Kingery, W. Christopher Boyd
• Format: Article
• Language: English
• Published: Elsevier 2020-01-01
• Series: Results in Chemistry
• Subjects: Cobalt; Azodioxide; Amination; Allylic alkenes; Catalysis
• Online Access: http://www.sciencedirect.com/science/article/pii/S2211715619300165

The unusual cobalt(II) diphenylazodioxide complex salts [Co(az)4](PF6)2 and [Co(bpy)(az)2](PF6)2 have been shown to catalyze the allylic amination/C–C double bond transposition reaction of 2-methyl-2-pentene with PhNHOH, with a turnover number of about 4. The mechanism is proposed to involve a nitroso-ene-like transfer of a PhNO moiety from the azodioxide ligand to the alkene, followed by reduction of the organic product to yield a cobalt(III) intermediate, which is itself reduced back to cobalt(II) by PhNHOH, regenerating PhNO. Hetero-Diels-Alder trapping experiments suggest that an “off-metal” mechanism, in which PhNO is released from the cobalt complexes and reacts with the alkenes, is operative, in contrast to an “on-metal” mechanism observed by Nicholas and coworkers for [Fe(az)3](FeCl4)2.