Highly stereoselective synthesis of chiral aldol polymers using repeated asymmetric Mukaiyama aldol reaction

Asymmetric aldol polymerization of bis(triethylsilyl enol ether) and dialdehyde was performed in the presence of chiral N-sulfonyloxazaborolidinone as a catalyst. The polymerization occurred smoothly at low temperature (−78°C to −20°C) to afford optically active polymers having unique main-chain structure of β-hydroxy carbonyl repeating unit. In order to estimate the asymmetric induction during the polymerization, asymmetric aldol reaction of triethylsilyl enol ether and benzaldehyde was studied as a model reaction. Optical purity of the chiral polymers obtained from the asymmetric polymerization was determined by using 1H NMR analysis after their chiral derivatization with (R)-O-acetylmandelic acid.