Asymmetric Polymerizations of Chiral 4-Benzyl-2-Ethynyloxazoline with Rhodium Catalyst and Chiroptical Properties of the Polymers

Researchers at Yamaguchi University in Japan have made new findings in the field of nanotechnology. The team, led by K. Onimura, has successfully polymerized optically active 4-alkyl-2-ethynyloxazoline derivatives (BnEOx) with rhodium catalysts, resulting in polymers with unique chiroptical properties. The study demonstrates the potential of these polymers in various applications, including the creation of chiral supramolecular aggregates.

Key Takeaways:

• The researchers achieved the highest absolute values of specific rotation ([α](D)=-77.3[°]) in toluene.
• The yields, molecular weights, and specific rotations of poly(BnEOx) were influenced by polymerization conditions.
• Copolymerization with phenylacetylene (PA) increased the molecular weight of the copolymer.
• The copolymers exhibited positive specific rotations ([α](D)=+4.7[°] to +62.5[°]) despite the negative sign of BnEOx and the homopolymer.
• The chiral/achiral copolymerization of BnEOx with PA gave copolymers containing higher order structures, such as one-handed helical conformation.
• The formation of chiral supramolecular aggregates was confirmed by induced Cotton effects in the p-p* transition region of conjugated main chain depending a complex of these polymers with zinc triflate salt in tetrahydrofuran solution.

Statistics:

• Highest absolute values of specific rotation ([α](D)=-77.3[°]) achieved in toluene.
• 4.7[°] to +62.5[°] positive specific rotations of copolymers.

Sources:

• Onimura, K., et al. (2011). Asymmetric polymerizations of chiral 4-benzyl-2-ethynyloxazoline with rhodium catalyst and chiroptical properties of the polymers. Chirality, 23 Suppl 1():E43-51.