posted on 2018-10-13, 00:00authored byMurat Alkan-Zambada, Xile Hu
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(N^N)(P^P)][PF6] complexes, where N^N stands for the
2,2′-bipyridine ligand and P^P 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.