Pd(II)-Catalyzed Asymmetric Annulation toward the Synthesis of 2,3-Disubstituted Chiral Indenols

An
enantioselective asymmetric annulation of 2-formylboronic acids
with internal alkynes has been realized using a chiral phosphinooxazoline/palladium­(II)
catalyst. The reaction tolerates a variety of alkynes including the
relatively inert diaryl substituted internal ones. A wide range of
optically active 2,3-disubstituted indenols was afforded in high yields
with good to excellent enantioselectivities (up to 99% yield and 99%
ee).