Design of Phosphinic Acid Catalysts with the Closest
Stereogenicity at the α‑Position: Synthesis and Application
of α‑Stereogenic Perfluoroalkyl Phosphinic Acid Catalysts
Chiral C2-symmetric phosphinic acids
were designed based on sterically demanding and helical chiral perfluoroalkyl
groups at the closest α-position advancing asymmetric reaction
environment and catalytic activity. The perfluoroalkyl catalysts,
[(CF3)2F2] and [(C2F5)2F2] phosphinic acids, were synthesized
via a stereoselective addition/cyclization sequence of methyl phosphinate
and deoxofluorination. These new classes of Brønsted acid catalysts
were applied to an asymmetric Friedel–Crafts reaction to give
up to 89% yield and 82% R-enantioselectivity, which
is higher than those obtained with the parent phosphoric acid (42%
and 55.5% S).