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DFT Study of Mechanism and Stereochemistry of Nickel-Catalyzed <i>trans</i>-Arylative Desymmetrizing Cyclization of Alkyne-Tethered Malononitriles
Present
here is a density functional theory (DFT) study of the
mechanism and origin of enantioselectivity of Ni-catalyzed desymmetric
cyclization of alkyne-tethered malononitriles and aryl boronic acids.
The reaction starts from transmetalation and arylnickel addition,
followed by trans to cis isomerization
to give cis-alkenyl nickel species. The stereodetermining
step is the CN insertion, which prefers a transition state with the
bystander CN group staying away from the ligand to reduce steric repulsion,
and gives the final (R)-product