Chiral
iridium complexes ligated by anionic oxazoline-bearing NCP-type
pincer ligands were developed and applied to the asymmetric transfer
hydrogenation (ATH) of diarylethenes using environmentally benign
ethanol as the hydrogen donor. High enantioselectivities could be
achieved for substrates bearing ortho-Me, ortho-Cl, or ortho-Br substituents on one
of the aryl groups. The ATH of ortho-Br-substituted
diarylethenes is particularly attractive due to the propensity of
the C(aryl)–Br bond to undergo various new bond-forming
events.