A Room-Temperature Catalytic Asymmetric Synthesis of Allenes with ECNU-Phos

Three-carbon
axial chirality has been asymmetrically established
from racemic one-carbon central chirality efficiently at room temperature:
we report here the discovery of the first catalytic asymmetric carbonylation
of readily available racemic propargylic carbonates to access optically
active 2,3-allenoates with fairly high ee. The combination of [(π-allyl)­PdCl]2 with [(R)-ECNU-Phos], a new
chiral bisphosphine ligand based on a biphenyl skeleton, demonstrates
high enantioselectivity. Both enantiomers of allenoates can be obtained
at room temperature by applying either (R)- or (S)-ECNU-Phos.