Cobalt-Catalyzed Asymmetric Addition of Silylacetylenes to 1,1-Disubstituted Allenes

The
asymmetric addition of silylacetylenes to 1,1-disubstituted
allenes proceeded in the presence of a cobalt/chiral bisphosphine
ligand to give the corresponding enynes with high enantioselectivity.
The results of deuterium-labeling experiments indicated that a hydrogen
atom at the chiral center is originated from the terminal alkyne,
and they were in good agreement with the proposed catalytic cycle
where enantioselectivity is determined by the reaction of the proposed
π-allylcobalt intermediate with the terminal alkyne.