title: Light-Induced C-H Arylation of (Hetero)arenes by In Situ Generated Diazo Anhydrides.
abstract: 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.
authors.affiliation: Institute of Chemistry, University of Graz, NAWI Graz, Heinrichstrasse 28, 8010 Graz (Austria) http://www.maos.net.
authors.forename: David
authors.initials: D
authors.lastname: Cantillo
authors.affiliation: Centro de Investigación Lilly S. A. Avda. de la Industria 30, 28108 Alcobendas-Madrid (Spain).
authors.forename: Carlos
authors.initials: C
authors.lastname: Mateos
authors.affiliation: Centro de Investigación Lilly S. A. Avda. de la Industria 30, 28108 Alcobendas-Madrid (Spain).
authors.forename: Juan A
authors.initials: JA
authors.lastname: Rincon
authors.affiliation: Centro de Investigación Lilly S. A. Avda. de la Industria 30, 28108 Alcobendas-Madrid (Spain). de_frutos_oscar@lilly.com.
authors.forename: Oscar
authors.initials: O
authors.lastname: de Frutos
authors.affiliation: Institute of Chemistry, University of Graz, NAWI Graz, Heinrichstrasse 28, 8010 Graz (Austria) http://www.maos.net. oliver.kappe@uni-graz.at.
authors.forename: C Oliver
authors.initials: CO
authors.lastname: Kappe
keywords: CH arylation; continuous-flow chemistry; diazo compounds; photochemistry; radical chemistry