Catalytic Carbocation Generation Enabled by the Mesolytic Cleavage of Alkoxyamine Radical Cations

• Published in: Angewandte Chemie (International ed.) Vol. 55; no. 34; pp. 9969 - 9973
• Main Authors: Zhu, Qilei, Gentry, Emily C., Knowles, Robert R.
• Format: Journal Article
• Language: English
• Published: WEINHEIM Blackwell Publishing Ltd 16.08.2016; Wiley; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: alkoxyamines; carbocations; Chemistry; Chemistry, Multidisciplinary; mesolytic cleavage; photoredox catalysis; Physical Sciences; radical cations; Science & Technology; ELECTRON; ACTIVATION; carbocations; C-C BOND; mesolytic cleavage; PHOTOCHEMISTRY; IONS; photoredox catalysis; radical cations; EFFICIENT; alkoxyamines
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201604619

A new catalytic method is described to access carbocation intermediates via the mesolytic cleavage of alkoxyamine radical cations. In this process, electron transfer between an excited state oxidant and a TEMPO‐derived alkoxyamine substrate gives rise to a radical cation with a remarkably weak C−O bond. Spontaneous scission results in the formation of the stable nitroxyl radical TEMPO. as well as a reactive carbocation intermediate that can be intercepted by a wide range of nucleophiles. Notably, this process occurs under neutral conditions and at comparatively mild potentials, enabling catalytic cation generation in the presence of both acid sensitive and easily oxidized nucleophilic partners. Carbocation intermediates can be accessed by mesolytic cleavage of alkoxyamine radical cations with a remarkably weak C−O bond. Spontaneous scission results in the formation of the stable nitroxyl radical TEMPO. and the reactive carbocation intermediate that can be intercepted by a wide range of nucleophiles.