Asymmetric group transfer polymerization of N-cyclohexymaleimide with Lewis acid and chiral ligand complexes

Asymmetric group transfer polymerization (AGTP) of N-cyclohexylmaleimide (CHMI) was carried out using ketene silyl acetal as initiator in the presence of Lewis acid-chiral ligand complexes to afford optically active poly(CHMI) ([alpha](435)(25) - 6.6 degrees to +31.0 degrees). Lewis acids used as GTP catalyst, probably activating the monomer by coordination, were zinc iodide, zinc bromide, zinc triflate, titanium tetrachloride, aluminum chloride and copper bromide. The zinc catalysts tended to accelerate the polymerization. The addition of trimethylsilyl iodide to the system accelerated the polymerization in spite of low temperature. Poly(CHMI) obtained in a poor yield with zinc triflate as Lewis acid and chiral bisoxazoline (Bnbox) showed low specific optical rotation and had the highest degree of polymerization (DP = 421, (M) over bar (n) = 75400).