Ruthenium(II)-Catalyzed Regioselective Ortho C–H Allenylation of Electron-Rich Aniline and Phenol Derivatives

Ortho
C–H allenylation of electron-rich benzene derivatives
with propargylic alcohol derivatives has been a challenge, due to
their great innate tendency toward a para C–H allenylation
via an SN2′-type substitution process. Here, we
described a Ru­(II)-catalyzed regioselective ortho C–H allenylation
of electron-rich aniline and phenol derivatives, which allows the
previously challenging synthesis of a broad range of ortho allenylated
aniline and phenol derivatives. More significantly, highly optically
active fully substituted allenes can also be prepared with high enantiomeric
excess via a highly efficient chirality transfer. No para C–H
allenylation product was observed in the current catalytic system,
thus showing a complete reversibility of the regioselectivity.