Specific Discrimination Polymerization for Highly Isotactic Polyesters Synthesis

Isotactic polymers have emerged with unique and excellent
properties
in material sciences. Specific discrimination polymerization provides
an ideal pathway to achieve highly isotactic polymers from their racemic
monomers, which is of great significance and a challenge in polymeric
chemistry. Although an enantioselective catalyst-mediated asymmetric
kinetic resolution polymerization (AKRP) process makes it possible,
a general and well-defined strategy for catalyst design is still rarely
reported. Here, based on a novel dual-ligand strategy, a new type
of chiral (BisSalen)Al complex with high enantioselectivity has been
described, in which perfect AKRP of racemic phenethylglycolide (Pegl)
is achieved for the first time. The more confined asymmetric microenvironment
formed by a dual ligand is the key to improve the enantioselectivity
of the original catalyst. To illustrate the generality of this strategy,
a series of (BisSalen)Al complexes with homo- or heterodual ligands
were designed for the AKRP of Pegl.