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.