Cu Photoredox Catalysts Supported by a 4,6-Disubstituted 2,2 '-Bipyridine Ligand: Application in Chlorotrifluoromethylation of Alkenes

Interest in base metal catalysis motivates the development of Cu-based photoredox catalysts for organic synthesis. However, only a few Cu catalysts have been applied in photoredox reactions, the majority of which contain one or two 1,10-phenanthroline ligands. Here we design a 4,6-disubstituted 2,2'-bipyridine ligand for Cu. Two heteroleptic [Cu((NN)-N-boolean AND)((PP)-P-boolean AND)][PF6] complexes, where (NN)-N-boolean AND stands for the 2,2'-bipyridine ligand and (PP)-P-boolean AND stands for a bisphosphine ligand, have been synthesized and characterized. They exhibit longer excited state lifetimes and higher Cu(I) / Cu(II) potentials compared to the most widely used Cu catalyst, [Cu-(dap)(2)]Cl. The complex with Xantphos as the P<^>P ligand is an efficient catalyst for chlorotrifluoromethylation of terminal alkenes, especially styrenes, which had been challenging substrates for previously reported photoredox reactions. This chlorotrifluoromethylation method enables the convenient introduction of a trifluoromethyl group into organic molecules under mild conditions, which is important for medicinal chemistry.