Catalytic enantioselective 1,2-addition reactions of
arylboronic
acids with 1,2,5-thiadiazoline 1,1-dioxide derivatives were achieved
using planar-chiral phosphine-olefin ligand L5 with a
bis[(2,3,4,5,6-pentafluoro)phenyl]phosphino group, showing ≤98%
ee. The enantioselectivities of the addition products were improved
by increasing the number of fluoro substituents on the aromatic ring
of the ligand. X-ray crystallographic studies of 3aa and
[RhCl/L5]2 revealed the absolute configuration
of the enantioenriched addition product 3 and the mode
of phosphine-olefin bidentate coordination of L5 to a
rhodium(I) cation.