Efficient Synthesis of an Unprecedented Enantiopure Hybrid Scorpionate/Cyclopentadienyl by Diastereoselective Nucleophilic Addition to a Fulvene

The work described here represents
the first example of an enantiopure
hybrid scorpionate/cyclopentadiene ligand. The ligand was obtained
in a one-pot synthetic procedure by an efficient and highly diastereoselective
nucleophilic addition of an organolithium reagent to an electrophilically
activated olefin in a new fulvene with a chiral substrate to control
the stereochemistry of a newly created asymmetric center. We verified
the potential utility of this ligand as a valuable scaffold that is
able to induce chirality in organometallic/coordination chemistry.
This was achieved through the preparation of a new enantiomerically
pure zinc complex in which the ligand behaves in a tridentate manner
with a κ2NN-η1(π)-Cp
coordination mode. This alkylzinc complex constitutes the first example
of an organozinc derivative which behaves as an efficient initiator
for the ROP of rac-LA in the production of isotactic-enriched
poly­(lactides) with Pi = 0.77.