Our group recently reported the use of [(DPEPhos)(bcp)Cu]PF 6 as a general copper-based photoredox catalyst which proved efficient to promote the activation of a broad variety of organic halides, including unactivated ones. These can then participate in various radical transformations such as reduction and cyclization reactions, as well as in the direct arylation of several (hetero)arenes. These transformations provide a straightforward access to a range of small molecules of interest in synthetic chemistry, as well as to biologically active natural products. Altogether, [(DPEPhos)(bcp)Cu]PF 6 acts as a convenient photoredox catalyst which appears to be an attractive, cheap and complementary alternative to the state-of-the-art iridium-and ruthenium-based photoredox catalysts. Here, we report a detailed protocol for the synthesis of [(DPEPhos)(bcp)Cu]PF 6 , as well as NMR and spectroscopic characterizations, and we illustrate its use in synthetic chemistry for the direct arylation of (hetero)arenes and radical cyclization of organic halides. In particular, the direct arylation of N-methylpyrrole with 4-iodobenzonitrile to afford 4-(1-methyl-1H-pyrrol-2-yl)benzonitrile and the radical cyclization of N-benzoyl-N- [(2-iodoquinolin-3-yl)methyl]cyanamide to afford natural product luotonin A are detailed. The scope and limitations of this copper-based photoredox catalyst are also briefly discussed.
Video LinkThe video component of this article can be found at https://www.jove.com/video/59739/ 4 , cheaper alternatives are still highly demanded for the development of complementary processes of interest for industrial applications. In this regard, the use of copper-based photoredox catalysts appears particularly appealing as they are not only cheaper but also provide opportunities to activate a broader and/or different range of substrates, which therefore opens new perspectives in photoredox catalysis 5,6,7,8 . Despite some promising early works reported by the Kutal 9 , Mitani 10 and Sauvage 11 groups, photoactivatable copper complexes have, however, only been scarcely used in photoredox catalysis, most probably because of their short-lived excited states compared to their ruthenium-and iridium-based congeners. More recently, recent remarkable contributions by Peters and Fu 12,13,14,15 , Reiser 16,17,18,19,20 and other groups 21,22,23,24,25 have clearly brought attention back to copper-based photoredox catalysts and demonstrated their unique potential.As part of our recent interest in copper-catalyzed radical processes 26,27, we recently reported a general and broadly applicable copper-based photoredox catalyst, [(DPEPhos)(bcp)Cu]PF 6 (DPEPhos: bis[(2-diphenylphosphino)phenyl] ether; bcp: bathocuproine), which turned out to be