Light-Induced C-H Arylation of (Hetero)arenes by In Situ Generated Diazo Anhydrides

    Dr. David Cantillo1, Dr. Carlos Mateos2, Dr. Juan A. Rincon2, Dr. Oscar de Frutos2 *, Prof. Dr. C. Oliver Kappe1 *

    • 1 Institute of Chemistry, University of Graz, NAWI Graz, Heinrichstrasse 28, 8010 Graz (Austria)
    • 2 Centro de Investigación Lilly S. A. Avda. de la Industria 30, 28108 Alcobendas-Madrid (Spain)

    Diazo anhydrides (Ar-N=N-O-N=N-Ar) have been known since 1896 but have rarely been used in synthesis. This communication describes the development of a photochemical catalyst-free C-H arylation methodology for the preparation of bi(hetero)aryls by the one-pot reaction of anilines with tert-butyl nitrite and (hetero)arenes under neutral conditions. The key step in this procedure is the in situ formation and subsequent photochemical (>300 nm) homolytic cleavage of a transient diazo anhydride intermediate. The generated aryl radical then efficiently reacts with a (hetero)arene to form the desired bi(hetero)aryls producing only nitrogen, water, and tert-butanol as byproducts. The scope of the reaction for several substituted anilines and (hetero)arenes was investigated. A continuous-flow protocol increasing selectivity and safety has been developed enabling the experimentally straightforward preparation of a variety of substituted bi(hetero)aryls within 45 min of reaction time.

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