Asymmetric gem-Hydroboration and gem-Hydrogenation of Ynamides: A New Gateway to Chiral Fischer Carbene Complexes and their Catalytic Transformations.

Ynamides, when reacted with H or HBpin in the presence of [Cp*RuCl], convert into chiral-at-metal Fischer carbenes by regioselective gem-hydrogenation or gem-hydroboration of the polarized triple bond, respectively. gem-Hydroboration concomitantly affords a carbogenic borylated stereocenter adjacent to the ruthenium carbene unit, the configuration of which can be controlled using an Evans auxiliary. These are the first examples of asymmetric gem-addition reactions to alkynes known in the literature; representative pianostool ruthenium carbene complexes formed by this unconventional route were characterized by crystallographic and spectroscopic means.